Tip #3: Computer Quick Test

If you see your engine light in the dash panel and you suspect the computer is the problem by the following symptoms:

Too many codes being displayed
The check engine light will not show or flash when turning the key on
Codes coming up is non-existent or not in the list supplied

Here are quick ways to find the fix:

Tap your computer housing gently with your hand and watch the dash. If connections are loose, the codes might show up.

Check the ground wire connections to the ecm, they could be loose, corroded. You can also measure the ground voltage. It must not exceed 0.250 volt. Higher than this value means a short somewhere in the circuit or the ecm itself. Ground wires are usually black in color. Finally, you can add your own ground wire to the ecm housing if you suspect a poor ground connection.

If the computer only acts up when hot, heat it up with a hair dryer and make voltage reading and see if there are changes. If the ecm is only acting up when cold, remove it and throw it to your freezer and test again.

Finally, take it out (with battery disconnected) and physically check the printed circuit inside for burns, corrosion by moisture.

Shown below is an example of a Chrysler computer.



Note the plug in terminals where the ecm pins are connected.