Symptoms of bad PCM?

Question

I have a 1997 Jeep Grand Cherokee and I have read that when getting my catalytic Converter replaced I should also reprogram the Powertrain Control Module. I know that I have needed a new converter due to the sound, but no indicators ever came on my dash, could this be a symptom? I have read this " The Powertrain Control Module contains software that may not be able to detect a failing catalytic converter. This can result in the failure of the "malfunction indicator light".

Also how much does it cost to reprogram the PCM if needed?

Answer 1

In my experience the reason to reprogram the pcm is to change the parameters on which the engine light would come on; mainly for catalyst efficiency codes. this will give the catalyst monitor a larger window to operate in before turning the check engine light on. If the converter is bad because of being restricted or plugged up I would suspect an air fuel mixture problem but if not it not unusual for a converter to become chemically inactive on a high mileage vehicle.

Answer 2

I would think that PCM reprogram would be no charge recall item. You should ask a dealer. A re-flash, or reprogram is pretty simple so it should not cost too much. Make sure you ask the dealer first because it might be free. As far as the sound telling you you need a new cat, that's not a great indicator. Good luck!

Answer 3

boy oh boy such questions! your control module uses input from sensors to set the engines perimeters. fancy way of saying it sets the tune specs to the engine. does it know if the cats bad? Not exactly but there are often 2 seperate oxy sensors designed into the system. the 1st reads the pre cat exhaust information , too rich, too lean etc the 2nd is behind the cat and reads the flow and how well re burned the exhaust is . this is a good sgnal a cat is bad. your PCM should be able to have the fault codes cleared disconeect the power from the batteys for a while and then drive several miles to get the pcm to "relearn" a light on the dash doesn't say the PCM is bad or good just that the sensors are speaking " complaining" the pcm stores fault codes for us to read later.

Answer 4

I work on jeeps all the time, I've never had to reprogram a pcm due to any failed parts on a jeep, also it wouldn't pick up any problems if the exhaust leak was after the o2 sensors.