The Diagnostic Port
Question for the week of September 8th, 1997
I've recently had problems with my Mitsubishi Eclipse that have been
difficult to track down. I suspect that the ECU might be bad. What can I do to
determine whether or not the problem is my ECU or not?
Figuring out ECU related problems can be very difficult
indeed. However, determining whether or not a particular problem is caused by
your ECU can be easy if you have a friend with a similar car. If the
ECU in your friend's car is compatible with your car, you swap the ECUs and see
whether or not the problem goes away. If it does, your ECU might have a
problem. If it doesn't, more than likely, your ECU is okay.
What ECUs are compatible with what cars? Compatibility in
the DSM line of cars is determined by three factors.
- The first is year of manufacture. Due to a wiring harness difference, the
first generation of DSMs is broken into two groups: 1989-1990 and 1991-1994. I
have yet to determine what the 1997 and 1998 models are compatible with -
however, the 1995 and 1996 DSMs can exchange ECUs.
- The second factor is engine type. The important groups here are 1.8l,
2.0l, and 2.0l turbo. There are different ECUs made depending on whether the
car is equipped with a manual or automatic transmission, or is FWD or AWD, but
for testing purposes, these differences really won't matter.
- The third factor is smog type. Basically, was the car made to adhere to
California smog standards or Federal smog standards? For testing, this really
doesn't matter too much - even if the ECU flags a CHECK ENGINE light or runs
rough, you will still be able to determine if the reason the #3 injector isn't
firing is due to the ECU. Also, at 1994 and beyond, all of the models share the
same smog equipment.
Past Diagnostic Port issues available.
Do you have a question about engine computers? Go ahead and