Check engine light obd2 code P0401 on 1998 Honda Accord

Symptom:

After the engine is started, check engine light is on and when scanned, code P0401 showed up. This code means insufficient egr flow. How do you test it?

Basic Concept:

First reset the ecm to remove the code and make sure it is not an intermittent code. Take the vehicle for road test until warmed up. Then decelerate the vehicle from 55 MPH at least 5 seconds and determine if the check engine light stays. If it does, scan for codes and see if obd2 code P0401 returns.

To fix this, remove the intake plenum by taking off all the plastic covers of the plenum. Unbolt the throttle body by removing the two nuts and two bolts. Then unbolt the intake plenum and disconnect all the hoses and electrical connectors at the rear. The throttle body can be tapped with a mallet where it connects to the plenum and it should come loose. The plenum can then be lifted and pulled out from the throttle body. Turn it over on a bench and use a 8 mm bit to drill out the EGR passage near the front of the plenum. All carbon deposit and debris must be removed and cleared. Once cleaned, everything can then be assembled using new gaskets. Reset the code and that should be it.

Notes:

For exact location of the exhaust ports to be cleaned, get hold of Honda Accord service manual or contact ATS.

Honda dealer should warranty this but phone them first.

Check engine light codes P1345 and P0300 on 1997 Chevy Suburban

Symptoms:

Check engine light showing with codes after scanning it. Engine seems to run OK but the light stays on all the time. It happened after the distributor was replaced.

The meaning for the following obd2 codes is:

P1345 crankshaft/camshaft position sensor correlation
P0300 ramdom misfire

The first code shows the relative position between the cam and crank sensor signals while the engine is running. The 2nd code could be the result of the first code. Fixing the first code can fix the 2nd code provided the latter code is not caused by other causes like mechanical or fuel system failure. Always reset the ecm code after fixing the first code to verify if the 2nd code is still present.

Fixing Strategy:

Fixing code P1345 requires checking the integrity of the distributor which houses the camshaft sensor. To check the distributor, check the cap and rotor visually and the measure the rotor movement to find any wear on the timing chain. Check also the power and ground supplies to the distributor when the ignition key is on. If OK, replace the crank sensor located at the front crank pulley. If all of these above are checked OK then using a scan tool, monitor the camshaft retard degrees setting. It should read 0+ or -2 degrees. Unfortunately, only a scanner can do this for you.

Note:

If you don’t have the special scanner to set up the camshaft/crankshaft sensor running degrees, just rotate the distributor so that the engine runs with its own power and take it to a garage so they can set it up for you.

Check engine light codes P0420B and P0430 on 1996 Ford Taurus

These obd2 codes indicate a failure for both catalytic converters (CAT) of this engine but the problem is the CAT is pricey (almost $1000 for both). How do you check the efficiency of the CAT?

Symptoms:

Both obd2 codes show up within 5 minutes of running the car.
Pinging when taking off

Here are a few common causes of CAT failures:

Poor quality gasoline fuel
Engine misfiring
Faulty oxygen sensors or not connected properly
Damaged exhaust system
Faulty coolant sensor
Faulty mass sensor
Excessive oil consumption

From the list above, if the problem is a sensor failure like oxygen, mass or coolant sensor, it should show when the codes are scanned. The same goes thru if there is misfiring on the engine. Take note that when the mass sensor is dirty or has failed, sometimes it will not show as a code. Try servicing this first before doing anything or replacing the CATs. Then monitor the readings of the oxygen sensors behind the CAT by manually making the mixture either rich or lean. This type of engine has 2 upstream oxygen sensors and 2 downstream oxygen sensors located after the CAT. When working normally, the downstream oxygen sensors fluctuate less than the front upstream sensors. A failed reading on the downstream oxygen sensor usually indicates a breakdown in the CAT. If the sensors checked out OK, replace the CATs but make sure to use Ford OEM parts.

Notes:

This assumes that the engine timing is set right after disconnecting the spout connector.
If you can get hold of a laser thermometer, measure the input and output temperature of the CAT. There should be 50 degrees difference after the engine is at operating temperature.

Check engine light OBD2 code P0172 on 97 VW Jetta

This P0172 obd2 code is coming on intermittently but the funny thing is, the engine runs good! What cause this obd2 code? How do you check it?

When this code shows up in your obd2 scanner, it means the bank 1 fuel trim or mixture setting is rich as calculated by your engine computer. This is determined by the oxygen sensor when it cannot make the mixture to get lean. This results in the computer commanding the injectors to spray more fuel than necessary causing the rich mixture.

Causes:

1.) Oil dilution especially if the oil level is high or the engine is worn causing blow by.
2.) Plugged pcv valve when restricted will cause a built up of oil vapour in the intake.
3.) Contaminated oxygen sensor probe which can supply erroneous signal to the ecm.
4.) Bad fuel regulator if the diaphragm is ruptured causing fuel dilution
5.) Bad mass sensor but check inlet screen first.

Most likely fix:

On most of these VW Jetta models, I would start with servicing the mass sensor first since the wire element of this sensor is easily contaminated. This is very common especially if the air filter is not changed regularly. After servicing the mass sensor, reset the codes before taking it for a test drive. A detailed way of servicing the mass sensor is available from ATS including the location and color of the wiring terminals.

Check engine light codes P0170 and P0173 OBD2 on 1999 Mercedes Benz SUV

This is another easy fix on these OBD2 codes if you know what to do. These codes are tricky because they come in pairs. However, the 2 obd2 codes are the give away to the problem. To fix these codes is shown below.

Symptoms:

Check engine light is always on with obd2 codes P0170 and P0173 when scanned.

These are the meaning of these obd2 codes:

P0170 fuel trim malfunction
P0173 fuel mixture out of limits

Basic Concepts:

Both of these obd2 codes are a by product of possible air induction problem such as vacuum leak at intake manifold, defective fuel regulator failure and even a worn engine. You can test the vacuum leak by using ATS water spray method but the best approach in fixing this is to service the mass sensor. As you will probably know, this sensor is exposed to a lot of abuse if the regular air filter maintenance is not done on schedule. If this is the case with your vehicle, service the wire elements of the mass sensor using instructions found in ATS past newsletters and this should fix the problem.

Remember to reset the engine computer after servicing the mass sensor. Also, if the cost of the mass sensor is not too expensive, you can replace it outright. To locate the mass sensor, get hold of a MB service manual or contact ATS.

Check engine light codes P0123 and P1596 for 1999 Jeep Cherokee

Beware when you see these 2 codes together on 1999 Jeep Cherokee. It is misleading because if you break down the meaning of each code:

P0123 is a failure in the tps circuit where signal voltage is higher than maximum setting.
P1596 is a failure in the cruise control circuit where the speed control switch is always high

Basic Concept:

On 1999 Cherokee, both the TPS sensor and the speed control switch are connected together thru a common brown yellow wire. This is a ground wire located at the right rear of the engine. However, this ground wire also passes the clock spring assembly located in the steering column. This clock spring is a triggering devise that helps activate the airbag and the speed control switch which sends a signal to the engine power train. This can be better understood if you have a wiring diagram of the cruise control circuit which shows in detail the various circuit flows of these components.

In layman’s language, as long as both tps and cruise control codes appear together, don’t try to fix this as if they are separate codes. Example; trying to replace the tps sensor and then fixing the cruise control circuit next are a no, no. The best approach to this is to monitor the signal voltage of the tps sensor and try disconnecting the clock spring terminals. If the clock spring is the culprit, the tps voltage should return to normal.

Notes:

When working on the clock spring, beware that the airbag could accidentally deployed and can cause injury. Please consult your service manual or authorized Jeep dealer.

Check engine light EGR P0401 intermittent code on 97 Toyota Camry

This P0401 egr code means insufficient egr flow at the egr valve. Problem is, it won’t show all the time and egr components look OK. How do you check this without the expensive tools?

Symptoms:

Check engine light coming on after engine gets hot
P0401 code detected

Basic Concept:

On this model, the egr system is composed of an egr valve the opens vacuum from exhaust to intake manifold, a vacuum modulator that regulates the amount of vacuum introduced to the egr valve and finally the egr vsv (vacuum switching valve) solenoid that directs vacuum flow to the egr valve after a command from the ecm. A quick way to test this is to manually pump 3-4 inches of vacuum to the egr valve during idle and the engine should stall. This shows the egr valve is working. The modulator itself is nothing but a regulator valve that that reduces the engine vacuum from 18-19 inches to 3-4 inches needed by the egr valve. This modulator pressure can be checked by teeing a fitting and measured by a vacuum gage.

Finally, the vsv solenoid can be tested with an ohmmeter to check the resistance of the windings. However, it is reported that this part has a high attrition rate because of it’s exposure to heat causing intermittent movement of the shaft inside. This is the part that should be checked thoroughly and replaced if possible.

To get location and wiring diagram of the vsv solenoid, get hold of a Toyota service manual or contact ATS.

Check engine lights for OBD2 codes

For domestic vehicles on 1995 and later models, a new on board diagnostic (obd) system for retrieving your check engine light is now widely used. This also applies on imports after 1993 models. The beauty of this system is the uniformity in getting the code. Now every vehicle whether it is a domestics or imports like GM, Ford or Chrysler, Toyota, Honda, BMW, etc…there is only one way of getting the code called OBD2.

Here are some important features:

1.) Diagnostic connector is located in a single location at the left side of the steering by the dash panel.
2.) The code numbering is the same for all types of car and trucks which promotes uniformity.

So what is the main the advantage of OBD2?

First, a garage or vehicle owner can avoid buying different scanner to get codes for different cars or trucks. This result in fewer tools required to get the code which will help in simplification of the process and at the same time speed up the fixing of the vehicles.

The good news for all vehicles drivers is… if you have a vehicle made after 1995-96; you can go to any local automotive parts store and they usually will offer a FREE scanning of the codes for you. They do this usually to help promote their parts.



Shown here is a Snap-On scanner that most independent automotive garages are using. This is expensive (cost at least in the 4 figure) but if you are doing a lot of vehicles, it will pay for itself. However, if you are driving only your own 1-2 vehicles, you can buy a cheap OBD2 decoder for under $50. The link to the decoder supplier is given if you are an ATS member. Fixing your check engine light is getting better every time.

Tip#25: Check engine light code 51 for 94 Dodge Spirit that causes rotten smell

Obd1 code 51 is an oxygen sensor circuit failure that makes the voltage reading stuck at a lower range (between 0.1 to 0.4 volt) showing lean conditions. When this happens, there is incomplete combustion causing Sulphur from the gasoline to mix with Oxygen molecules resulting in rotten egg smell at your exhaust. Diagnosis to this problem is detailed below.

Symptom:

Code 51 showing lower voltage readings instead of the fluctuating normal voltage.

Basic Concept:

This car has a 3 L engine and an oxygen sensor with 4 wires at the exhaust. Two wires are for the heater circuit and the other two is for the fuel mixture. As discussed in other previous blogs, the voltage reading can be manipulated by manually adding fuel or more air to the intake system. During this time, the voltage at the sensor signal wire should change and oscillate. Otherwise, the sensor itself has failed.

Problem will be get complex if after replacing the sensor; it fails again after a few weeks which suggest only one thing: CONTAMINATION. Causes? There are some engine self induced factors that will cause premature failure of the sensor including:

Coolant contamination caused by head gasket or cracked cylinder head.
Oil contamination caused by oil dripping directly to the sensor from the steering switch.

Both problems can be tested and checked visually using proper tools. Use Dodge service manual or ATS.

Tip#24: Check engine light code 13 for early Toyota Pick ups

This code 13 is an ignition circuit failure caused by a loss of “NE” signal from distributor to the ecm (computer) after 2 seconds the starter signal called “sta” is received by the ecm. Testing procedures is described below.

Symptoms:

Code 13
No start when engine cranked
Failed smog test including rough idle
Misfiring, cutting out and stalling

Basic Concepts:

Without a specialized tool like the ones used by a garage, this will be a little tough for a vehicle owner but using a voltmeter, measure the 12 volt supply from the ignition switch to the distributor. With engine key on, this 12 volt supply can be confirmed easily. If the engine does not start, use a test light and test the negative wire going from the distributor to the ignition coil. This wire should blink while cranking the engine. With these 2 tests, here are the possible culprits:

Bad igniter or ignition module located inside the distributor
Bad ignition coil
Bad NE wiring from the ecm and distributor
Bad ecm

The ignition coil can be removed and tested for comparison voltage with a new coil
The igniter can also be removed and tested except it is very expensive
The NE wire can be substituted with a jumper wire from distributor to the ecm usually located in behind the front kick panel
ECM seldom fails on Toyotas and this is the last option

Note:

NE wire is very common problem on this which is caused by poor insulation and routing.

Tip#23: Obd1 code 13 oxygen sensor for a 1993 Chevy S10 truck

If you get a check engine light code 13 for an obd1 system on 93 S10 truck, it means a failure in the oxygen sensor circuit. Assuming a vehicle owner has a voltmeter, the oxygen sensor has 3 wire connections and one of them (purple in color) can be tested for voltage signal to the ecm (computer). So how do you proceed to repair this problem besides replacing the oxygen sensor itself?

Symptoms:

Code 13 oxygen sensor after retrieving code from diagnostic connector.
Voltage reading at purple wire stuck at 0.400 to 0.475 volt all the time.

Basic Concept:

As discussed earlier in previous blogs, when you get a check engine light with oxygen sensor failure, the signal voltage should oscillates between 0.1 volt to 0.9 volt if it is working normally. In this case, our reading is stuck at 0.4-0.47 volt when tested. To eliminate the possibility that the oxygen sensor itself is the problem, you can inject a carb cleaner spray to the TB (throttle body) and the voltage reading should go up. If not or the reading is still stuck, 2 things are possible:

The oxygen sensor itself is bad
The purple wire connection to the ecm is no good.

The first can be easily fixed by replacing the oxygen sensor and the code reset. If the obd1 code 13 remains, it means the wiring connection from the oxygen sensor to the ecm terminal is buggered up. A long jumper wire can be substituted between the sensor and ecm and the reading verified. This should solve the problem otherwise; the ecm itself must be checked.

Tip#22: Obd1 332 DPFE sensor code for 94 Ford Explorers

When checking for check engine light and code 332 appears, the normal procedure to repair this code is check and repair if necessary the egr valve, the evr solenoid or clean the passages between the egr and your intake ports. However, after doing all of these, the obd1 code returns because a lot of guys forget the dpfe sensor and most of the time, this is the culprit!

Symptoms:

Code 332 displayed after scanning the codes
Engine stalls when vacuum is manually applied to the egr valve

Basic Concept:

On most OBD1 Ford 92-94 egr system, the egr valve has a dpfe sensor sitting on top of the egr valve. What is does is measure the pressure going between the intake manifold and exhaust manifold. The difference between the 2 pressures is sent as an output signal to the ecm. As a result, the ecm can calculate the proper vacuum flow thru the evr solenoid and egr valve. If this dpfe sensor is defective, the vacuum flow might not be enough causing an issuficient flow resulting in obd1 code 332.

Testing the dpfe sensor is simple. Just apply 8-9 inches of vacuum using a hand held vacuum pump to the intake port opening. Then measure the voltage to the center wire of the 3 terminal plugs in of the sensor. You will notice the reading is about 4 volts or more. As soon as you release the vacuum, it should go down to 1.5 volts within 3 seconds. If it is not doing this, replace the sensor. Double check also the hoses going to this sensor before replacing it.

Tip#21: No check engine light on 93 BMWs

If you have a short in your vehicle electronics system, scanning for the fault codes maybe impossible because the check engine light will not come on. So what is the meaning of this for you? It means if your engine has a failure electrically, you cannot access or retrieve the codes.

Symptoms:

When you use either method like putting a jumper wire to the diagnostic connector or hooking up a generic scanner, the dash light does not blink or the scanner does not work.

Basic Concept:

In a typical BMW vehicle computer system, there are a few control modules involved. These are transmission module, abs module, engine control module, AC module, steering module, air bag module, etc. If one of them is shorted, then the rest cannot be contacted by the scanner. What to do? Here are some tricks you can do so you can make the car’s computer come alive again:

1. Try disconnecting both positive and negative battery terminals and touch them together for at least 60 seconds. Doing this will reset the codes if the problem is not serious.

2. Hook up the jumper wire to the diagnostic connector or your scanner. If it does not communicate, try disconnecting the module one at a time. Watch the result while doing this until the scanner or the check engine light blinks. The last module you disconnect where the scanner works is the culprit. Always start with the trany module because it has the highest rate of failure.

Check with your BMW service manual for the modules wiring diagram or contact ATS

TIP#20: Check engine light with code 32 on 94 Dodge Truck

Code 32 refers to failure in EGR solenoid that controls the vacuum supply to the EGR valve. When this happens, a check engine light shows up in your dash panel.

Symptoms:

Code 32-egr solenoid circuit failure

Engine surging cause by too much air coming in and the computer trying to push more fuel in the injectors to compensate

Engine misfire especially under load since the mixture is lean

Rough idle and dies as soon as you put the trany in drive

Basic Concept:

When your egr solenoid fails, the vacuum supply to the egr valve could be stuck open allowing uncontrolled intake air to get in to your combustion chamber. As the computer try to balance the mixture, more fuel is sprayed in the throttle body where air and fuel are mixed. A quick way to test this is to unhook the vacuum hose going to the egr valve and see if the symptom will stop. If it does, service the egr valve. If code 32 shows up, check the solenoid for winding resistance and compare with a new one. You can also try to supply your own power (12 volts) and ground to make it work.



Shown here is an electronic egr that eliminates the need for egr valve. It has about 3 solenoids inside and it controls 3 vacuum openings.

Tip#19: No check engine lights on 94 Toyota Camry and acting up?

The best approach in testing your vehicle problem is to watch your dash panel. Observing the check engine light should give you a hint what is going on inside your engine. However, what do you do if the computer does not display anything when you connect the diagnostic connector?

Symptoms of Toyota Camry:

Intermittent no starts
Will run a few minutes and quit
No check engine light displayed when codes are accessed

Basic Concepts:

Using your basic, always start with the check engine light in the dash. As soon as it starts, does the light stays? If it does, it’s a computer or electronics problem. You can access the code by jumping diagnostic terminals TE1 and E1 and watch the codes being displayed. If the computer does not communicate, most likely the computer is buggered up. Here are some procedures before replacing it:

Take out the computer and have a visual inspection on its terminal pins, connections. Using basic computer test, check presence of voltage on power supply terminals but the most important is to measure the voltage readings of all ground pins. Having a voltage reading higher than 0.250 volt indicates something other than the computer is defective. If you replace the computer without correcting the ground problem, you will damage the computer again.

This fix assumes:

You have done the basic tune up like replacement of plug wires, plugs, cap and rotor including fuel filter.
Cleared the integrity of the fuel regulator and serviced the mass sensor as shown earlier in this blog.
You are familiar with testing the computer as shown in ATS course.

Tip#18: Check engine light code 16 on 92-94 BMW318is

This check engine light codes faults the cam sensor and most garages will replace it automatically but don’t do it if you want to save money.

Symptoms:

Frequent no starts which can occur anytime
Code 16

Basic Concept:

The computer of this engine is called DME. For the code 16 to appear, it means the DME did not received any signal from either crank or cam sensor. When that happens, the fuel relay will not get a ground signal from the DME. Also, the computer will store a code 16 when that happens causing your check engine light to come on.

Tests:

When no start occurs, check your spark for integrity like: Is it consistent? What color? As soon as it shows that the spark is gone or weak, test the crank sensor wirings for cuts, insulation or shorts. You can also measure the ac voltage of the sensor while cranking and compare it to specs. Some parts store will also allow you to compare the resistance reading with a new one if you remove the crank sensor. Also test the integrity of your injector signal if it is working using a noid light tester. With no spark and presence of injector signal, replace the crank sensor first and see if the code returns. If it does, that is the time to replace the cam sensor especially if the injectors are not working. Remember: Don’t change any part until you test the part or circuit.

Always reset your computer after fixing your check engine light codes. For detailed method of testing, get hold of a BMW service manual or contact http://www.automotivetroubleshootingsecrets.com.

Tip# 17: Check engine light code 42 for early 90s Chevy 3.1L engines

This code calls for ESC (electronic spark control) circuit failure which deals primarily with ignition. In other words, ignition parts that help produce spark such as ignition module, plug wires and coil. In this problem, the engine has no distributor and you can expect to investigate the crank sensor which is located either in the front or rear of the engine.

Symptoms:

Code 42 when accessed
Intermittent no start with misfire and hesitation
Starts and idles fine but as soon as you put it in drive, engine stalls

Normally, the symptom looks like a trany tcc (trany torque converter) problem if there is no code 42 code which is ignition related. Since the engine has a crank sensor, begin by checking for ac voltage on the sensor terminals while cranking. If no reading, either it has bad wiring or bad ecm (computer) provided there is 12 volt supply going to the ignition module. If there is an ac reading, the crank sensor is probably defective and you can check that by comparing the resistance with a new crank sensor. To save time, always replace the crank sensor and ignition module at the same time since they always work together. Once replaced, reset the codes and verify if the same code 42 comes back.

Notes:

1.) This check engine code is easily fixed provided you have a wiring diagram to trace the ignition components. Contact your local Chevy dealer or see ATS.

2.) This code problem assumes that the ignition coil and plug wires are tested OK.

3.) On Chevy Lumina 3.1L engines, there is a common wiring short always occurring between the crank sensor and ignition module connections.

Tip #16: Check engine light with EGR sensor code for early 90s Ford vehicle.

A check engine light code 327 on a 92-94 Ford with 4.6 L engine indicates low voltage signal for the EGR circuit. When tested, the DPFE sensor which controls the vacuum supply to the EGR valve was found defective and replaced. The EGR valve was also replaced after resetting the code which showed another EGR code 332 showing up.

Symptoms:

When you have an EGR circuit failure, the engine acts like having a vacuum leak. This makes your fuel mixture go lean resulting in stalling, hesitation and either rough idle or surging.

Common Repair:

When servicing your EGR system, make sure all the vacuum passages between the EGR valve, DPFE sensor and intake manifold are clear. Most of the time, the tubes are removed and cleaned to make sure vacuum flow is not restricted. Doing this will save you a lot of time and grief.



Shown here is an example of an EGR valve with vacuum hose connected on top.
Using a vacuum diagram, the EGR vacuum passages could be serviced and cleared.

Tip #15: Check engine light with oxygen sensor code for 94 BMW

If you have a check engine light in your 1994 BMW with codes 12 or 13, it means the oxygen sensor circuit is faulty. Don’t rush and replace the sensor right away but test the oxygen sensor voltage reading to confirm if it is really defective.

Symptoms:

Check engine light in the dash is always on
Engine runs rough despite changing the spark plugs and wires.

Oxygen sensor monitors the fuel mixture condition of your engine. The info gathered is fed to the engine computer which then decides the amount of fuel to be injected to your injectors. If the info says lean, the computer will command the injectors to spray more fuel and vice-versa.

Testing:

You can measure the voltage of the oxygen sensor while the engine is running by hooking up a voltmeter on the sensor’s signal wire. The reading should be oscillating from 0.1 volt to 0.9 volt. To test, spray some carb cleaner to your throttle plates and the reading should stay in the upper range (say around 0.7 to 0.9 volt). You can also unplug any vacuum line to allow more air causing lean mixture and this will cause the reading to hover in the lower range like around 0.1 to 0.3 volt. If the sensor is not reacting when you do these, the sensor is bad. Otherwise, look for the causes of the oxygen sensor code like vacuum leak, gasket leak, sensor wiring problem and etc. More detailed test is available if you are a member of ATS including later models of BMW.

Tip #14: Testing TPS sensor check engine light codes

TPS or throttle position sensor monitors the movement of your throttle linkage when you step on your gas pedal. A quick way to find it is to follow the linkage rod or cable connected to your gas pedal. You will find it ends on the throttle body (TB) below the air filter housing. On the side of this TB housing is the tps sensor accompanied by 3 wire terminals: one for ground, second for 5 volt reference and the 3rd one: the signal wire.

How to check your tps sensor?

You don’t even have the engine running to check your tps sensor. Just access the middle or 3rd wire and using a voltmeter, measure the voltage against the vehicle ground. With throttle on close position (the setting where the engine runs at idle), the voltage should be around 0.5 volt. Now move the throttle linkage to full or wide open throttle position (just like flooring the gas pedal to get max fuel and speed). The reading should be from 4.5 -5 volts. If the tps sensor is not getting this range, then the sensor is bad. Remember to turn the key on when performing this test.


Shown here is an example of a tps sensor.

This applies to most kind of vehicles whether domestics or imports. If you need the exact wiring diagram for the middle (signal) wire, contact your local dealer or ATS.

Tip #13: Testing 94 Chrysler computers with ignition code

Chrysler engines computer in 1994 models is used to fire the ignition coils which produces spark. Instead of the regular set up where the ignition module is located remotely in your distributor or under the ignition coil, the ignition module is located inside the engine computer. Assuming you have no spark and has a check engine light flashing in your dash, what do you do?

First, verify the check engine light by retrieving the code using the ignition key. If you have an ignition fault code like 43 which means ignition coil failure, try replacing the ignition coil first. Then confirm the code by resetting the computer and see if the engine will start. Assuming you get the code again and has no spark, we can assume the only 2 causes of this problem will be:

1.) Wiring connections between the computer and ignition coil.
2.) Faulty engine computer

We can eliminate the wiring problem above by running our own wires between the ignition coil and computer and supplying power to the ignition coil direct from the battery. This leaves the engine computer as the only other possible source of the problem if the code or no start persists. Therefore, if it does not start and still the code returns, we can safely say the engine computer is defective.

Shown below is an example of Chrysler engine computer.


Remember to disconnect the battery before removing the computer.

Tip #12 Crank sensor code 2 for 1994 Mazda V6 engines

If you encounter a crank sensor code like # 2 for your V6 Mazda engine, please take note of this because it might happen to you.

Symptoms:

Check engine light coming on at low speed but goes away under acceleration and if you access the code yourself, you get a code 02. This code is usually hard to diagnose because the only thing you can do if you are working at home are:

1.) Check the wiring connections leading to the sensor and making sure the connections are tight and test for signs of cuts, shorts or poor connections.
2.) Measure the resistance of the crank sensor (about 900-1200 ohms) using an ohmmeter after disconnecting the crank sensor wiring terminal.

If above tests are OK, most mechanics when confronted with this will replace the crank sensor and if the check engine light is still present, replace the computer?

Fix:

The computer replacement might be the obvious next choice but before doing that you may want to check your distributor first especially these parts:

Distributor cap, if aftermarket replace with OEM part
Distributor rotor, if aftermarket replace with OEM part

It is found that aftermarket parts used for Mazda are far inferior when compared to the quality of materials being used. Most garages will not use them and only used dealer (OEM) parts only. Save yourself the head ache by making sure you use OEM parts only. After replacing these parts, reset the code and go for a road test. Most of the time, the above code will go away but if it comes back, that is the time to check the computer circuit.

Volkswagen vehicles obd1 codes retrieval

You can access your check engine light codes in Volkswagen vehicles for vehicles made from 1988 to 1994. It is done using 2 ways: one type using a rocker switch located at the bottom at your dash panel and a second type using a jumper connected to the diagnostic connector located in the console

When activating the codes using the fist type, press and hold down the rocker switch for 4-5 seconds and with ignition key on, engine off. Release the switch after the code starts flashing in the dash (see “check” light in the dash) and press and hold it again for 4-6 seconds and the rest of the codes should continue flashing.

Using the jumper wire, connect the black end of the jumper wire to the black diagnostic connector of the center console while the white end of the jumper wire connects to the white diagnostic connector of the center console. The jumper wire is available from the dealer and is called “wire cable 357 971 514E”. This jumper wire must be connected for 5 seconds and remove after the codes begin flashing.

For both systems, a code is flashed at 2.5 seconds each and comes as a four digit codes. As soon as you get codes 4444 or 0000, it means the end of the code and it can be stopped by turning the key off. After performing repairs and if you do not get code 4444, it means the problem is not fixed.

To clear the codes, wait until code 4444 is displayed and turn the ignition switch off. Connect the jumper wire to the diagnostic connectors again and turn the ignition switch on. Leave the jumper wire for 5 seconds and wait if code 4444 to appear again. When it does, the codes are erased and the ignition switch can be turned off and jumper wire remove.

Here are common obd1 Volkswagen codes 1988 to 1994:

Code 4444 No fault indicated
Code 2212 Throttle valve potentiometer fault
Code 2312 Engine coolant sensor fault
Code 2322 Intake air temperature sensor fault
Code 2342 Oxygen sensor fault
Code 2141 Knock sensor fault
Code 2341 Oxygen sensor control (vacuum or exhaust leak, wiring fault)
Code 2323 Air flow sensor fault
Code 4411 Fuel injector fault
Code 1111 Control unit
Code 0000 End of code transfer: 2.5 second flashes at 2.5 seconds interval