Bearstream

PCM keeps kicking out a check engine light, pulled battery ground, resets fine for a while, then kicks out a check engine light, codes the P0601, I’m suspicious of a PCM ground, got to figure out where to look, so I can smog cert…2003 WJ 6 Cyl.

Cherryokee

Hi Bearstream, look at this screen shot from my 2000 WJ FSM. You're looking for G103 and it's in this image. There is a splice to check also, called S138, leading to the data link connector. It's a Black/Orange 20AWG and should also be found at G103. Good luck.


PCM and G103 location

Bearstream

Thanks for the screenshot, it gives me another place to look, bad grounds cause all types of strange problems. BTW, I’ve bought a number of Jeep parts from Quirk up in your area, the last place in the country that had the parts I needed, sometimes you got to get them wherever you find them.

Cherryokee

I went on a "bad ground" search-and-destroy mission last fall and I found that all of the braided ground straps had disintegrated. After adding new straps and cleaning grounds the electrical gremlins, rough idle and noise in the radio went away. Quirk is a good go-to for hard to get parts. They were a high volume Jeep dealer for a long time and I think they warehoused a crapload of parts. Good luck with that "quirky" PCM!

Bearstream

The ground lugs were a little crusty, scrubbed them good, reassembled with corrosion inhibitor, so far so good, multi-meter showed clean continuity, hope that solves it…

Bearstream

Cleaned up contacts, still getting the P0601 code, tried a few resets, but they didn’t hold, I may try a reset and drive it awhile and see if it recovers the sensor inputs. My WJ sat for six weeks while I was recovering from a knee replacement, got out and started it several times to keep the battery charged. May have something to do with it…Smog Tech said the PCM wasn’t getting a complete read from one of the sensors, and suggested I drive it to allow the PCM time to register the data from the sensor, I’ll give it a go, everything else works fine…

Bearstream

Well, the Smog Tech’s computer indicated O2 sensor heater “not ready” , so it looks like they’re going to need a diagnostic check a with the multimeter. Quite possibly could be failing at 210,000 miles, also noticed a slight bobble with the idle, otherwise no other issues. If O2 sensors need replacement, I’ve heard NGK/ NTK are closest to Mopar OEM in terms of PCM system compatibility, any suggestions welcomed…

Gr33ntr@nsformer

Hello I'm new to this forum and don't really know how to use it so hopefully someone's sees this this and can help me out. I have a 1998 grand cherokee lardeo. So when I first got it it had cracks in the front transmission lines and was spraying all over the exhaust pipe causing white smoke got that fixed. So then the jeep wouldn't turn over some times and would die randomly. Since then I've had the jeep for a few months now I've changed the spark plugs, coil and crankshaft position censor. I also found out the fifth cylinder wasn't working properly so I changed the pin. So the jeep still dies randomly and I think it's the pcm. I went through car computer exchange and they sold me a faulty computer that didn't work. Does anyone know of a credible website I could buy an aftermarket part like that from.

Bearstream

Did you plug in an OBD2 and see what P-codes it was displaying? Also if you click the ignition key off and on 3 times, the odometer will display a P-code if there is a system fault. Best place to start your search before buying parts, I’m in the same position, as a retired geezer, I can’t afford to spend more than necessary, so I’m in progress of diagnosing an issue with the O2 sensors, so I’ll pass California smog testing. I was initially inclined to replace the PCM, however my research took me in a different direction pointing to faulty O2 sensors.

Bearstream

Went through all O2 sensors with digital multimeter, up and down sides, and all seemed to be working within parameters, yet I’m still getting the check engine light with a P0601 fault code, not looking good for the PCM unit, not quite sure what to look for now…If it needs replacing, I’ll have to find a reliable replacement, as I know there are some out there that are garbage…

Bearstream

OK, bought a rebuilt PCM, starts up and runs for 5 seconds then quits, PCM doesn’t recognize ignition key SKIM chip, any way to bypass this anti-theft feature, the WJ is 20 years old, I’m not overly worried about it being stolen, I just need my rig to run…DANG IT!!!