Car is running poorly as of late, Runs fine when cold then beggins to idle rough and tug a little while driving. THe Ecm is throwing a code 45 and code 42. Oxygen sensor is new, EGR seams to be working, the last thing haynes states for both of these codes is a bad ECM. I can get a used ECM for 50 bux from the local wrecker. If I swap out the ecm for the one from the wrecker, do I have to put in my prom?.

 

If the ecm (I'll assume its a 7730) is not from the SAME ENGINE, then you do need the eprom from your car. The Memcal has both the eprom and ESC circuitry for "limp mode". If you get an SES light, with the other Memcal...you could end up being stuck if it is too far off (ie V6 vs V8 car).

BTW, code 45 means "Rich O2 Sensor", just because the O2 sensor is new, doesn't mean it is good. You need a scan tool to see if you are getting the proper "cross counts" around 450 mVs.

Maybe you have a short somewhere.

 

Code 42 is also the code for the ignition module if I remember correctly and what you describe sounds like it could be an ignition module failure. YOu could pull it and have it tested. I replaced mine for $25 two days ago. That was the 7 pin. If yours is 4 pin it's like 60. Just a thought ~Arnold

 

The ignition module is also something I've considered. I'm not sure how to change it though.

 

Now that you have some "serious answers", I will say what I initially thought when I saw your post "How do you tell if ECM is Bad"?

Simple, it starts staying out late, comes home drunk all the time and you find money missing from your wallet.