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.