Resetting the PCM

OB · Post by OB » Wed Nov 22, 2006 2:26 am

So my dads neon was throwing a code a few months ago, which i traced and found INVALID SKIM KEY as the culprit. we kinda forgot about it, since it wasnt a huge deal, but his car has been acting up lately and it actually died the other night, while stopped at a stop sign. anyways, im workin on diagnosing this over the phone, and when he drove it around with me the other day I noticed that it idled very low (600-700) and started to stumble. it died once, and it felt very intentional, like the car turned itself off. it no longer throws the code, but i still think the immobilizer is behind all this, so I want to restart the computer to see if we can get the code to show itself again. what is the best way to 100% restart the PCM and all systems? Ive heard some people say to unplug the neg battery cable and let the car sit for 30 mins or an hour, and that does it. Others say that the car wont restart unless the fuel relay is pulled. The battery option makes the most sense, but i wanted to confirm. thanks and any help in figuring this out would be appreciated. I dont have a lot of time to work this out seeing as how im so busy with work and school.

white2000neon · Post by **white2000neon** » Wed Nov 22, 2006 7:52 am

Unplug the negative battery terminal. I tried to pull the fuel pump relay and it did not reset my ecu. To speed the process unplug the negative terminal and hit the brakes afterwards to drain as much power thats left in the wires so you only have to wait like 10 minutes or so.

BlackRoseRacing · Post by **BlackRoseRacing** » Wed Nov 22, 2006 8:31 pm

white2000neon wrote:Unplug the negative battery terminal. I tried to pull the fuel pump relay and it did not reset my ecu. To speed the process unplug the negative terminal and hit the brakes afterwards to drain as much power thats left in the wires so you only have to wait like 10 minutes or so.

Ive tested this with a multimeter, stepping on the brakes for 1minute still did not totally discharge the pcm from any voltage...
The best luck I have had(without further testing) is to disconnect the battery, unplug the fuel pump relay and let it sit overnight.....
I have not sat down and tested on how long it actually takes, but the easiest way to do it is what I stated above....

OB · Post by OB » Thu Nov 23, 2006 2:42 pm

Ill use my DMM when i do it and use some techniques i learned at school to test static voltage. turning on the headlights for 15 seconds is one of the things we do to clear voltage at the battery, but the PCM is something im not too sure about, as i varies from car to car. I know they can hold amperage for quite awhile, so ill just have to let it sit for a few hours. thanks guys