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Discussion Starter · #1 ·
Howdy, all. Got an '04 WJ (4.0L) automatic trans, with around 130,XXX mi that I'm having a few different issues with. Hoping to find some guidance here! Sorry in advance for being long winded.

1. More consistently over the last couple months it's been giving electrical issues (prior to this it's been once in a blue moon - no rhyme/reason) Every so often when turning the ignition switch on (but before cranking) all electronics will be dead. Almost as if the battery has been disconnected. The instrument panel lights will flash, and all the gauges (tach, speedo, voltmeter, etc) will all come alive and then die within a second. I let it sit for a few minutes and then everything operates as normal. Back in June, while on a road trip, it did this while I made a pit stop. After electricity came back on and got back on the road, the voltage was fluctuating between 12-14 or 15 volts, headlights were flickering like a candle, and when I turned my brights on all the warning lights came on the instrument panel. When I cycled my A/C on and off, this reset the warning lights. My limited knowledge let me to thing it was a simple voltage regulator (I'm used to working on Squarebody Chevys - ha!) and that's when I learned more about PCM failures. Is my understanding correct the voltage regulator on an '04 WJ is in the PCM?

2. Around the same time as the electrical issues began over the last 2 months, it's also started stalling when I put it in reverse when the engine was warm or hot. No electrical failures with the engine stall. It just dies like cutting the switch off. First start and drive of the day (or between drives when the engine cooled down) everything operates normal. Now it's grown into more anytime I shift into reverse, regardless of engine temp.

3. Within the last week it's been stalling in forward gears too. It was wanting to stall at low RPM at a stoplight, and did stall while crossing a parking lot. Took it for a test drive last night after it sat for week, and it stalled again in a parking lot where I was turning around. Cranked it back up, and let it idle for a minute, and then it just died. Couldn't get it cranked back up after that - almost as if the fuel pump was dead (couldn't hear fuel pump running.) When I was trying to start it back up, it was backfiring and spitting like the timing was off. Went back to tow it home this morning, and it fired right up and I immediately drove it home (less than a mile.) Obviously, I would think this means the fuel pump is working. Going to test the fuel pressure now. Now I've got it in my driveway where I can start to try and diagnose different issues.

I'm kind of at a loss on where to start with this. My initial thoughts are possibly:
  1. Failed cam and/or crank sensor
  2. Failed fuel pump
  3. Failed neutral safety switch
I've cleaned all the grounds around the engine bay, cleaned the battery terminals, and unplugged/replugged the PCM.

Could a PCM failure be the root of all these other problems? I get where if it's bad, it'll throw the timing off, and possibly give electrical issues.

If it is a PCM failure and it has to be replaced, what does that generally look like? From what I understand either a dealer or mechanic with the software has to flash a replacement PCM specifically for my VIN. Is there a decent success rate on replacing a PCM?

Am I also correcting in that MOPAR doesn't make these PCMs anymore, and that I'd have to buy a reman/refurb one?

Should also note that this WJ had an aftermarket alarm system installed by a previous owner. I'm concerned that it's fried the PCM. I had a similar issue with the ECM on an '02 Dodge Ram, and was basically told there was nothing anyone could do. It had been fried by the aftermarket alarm/remote start system.

Any guidance is much appreciated. Trying to research what I can instead of just throwing parts at it.

Thanks in advance!
 

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Yours sounds similar to Minnesota…not sure yours is a crank sensor, but my Aurora did just about everything yours is doing, and it was cleared up with a crank sensor. If the computer doesn’t get a crank signal, it just sits there and waits. It does not know how to predict the next firing event, it just waits to be told what to do.
 

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Discussion Starter · #3 ·
Yours sounds similar to Minnesota…not sure yours is a crank sensor, but my Aurora did just about everything yours is doing, and it was cleared up with a crank sensor. If the computer doesn’t get a crank signal, it just sits there and waits. It does not know how to predict the next firing event, it just waits to be told what to do.
Thanks, Ntrenn. Spent some time this afternoon cleaning the battery terminals and that seemed to help with the odd electric issues.

I let it sit for a couple hours again and then it cranked right up. Ran for about 2.5 min and then quit again and wouldn't fire up. Did your Aurora act similar?
 

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not cranking would have me look at the battery cables - both ends, the terminal clamps- TIGHT?
The positive feed to the PDC.
Do scan of the sysem post ALL codes, at least key on off trick if no scanner.
Do you have BOTH keys and used both?

Whats your skill level - comfortable with a test light and a wiring diagram ?

Was anything electrical changed or added?
 

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not cranking would have me look at the battery cables - both ends, the terminal clamps- TIGHT?
The positive feed to the PDC.
Do scan of the sysem post ALL codes, at least key on off trick if no scanner.
Do you have BOTH keys and used both?
Whats your skill level - comfortable with a test light and a wiring diagram ?
Was anything electrical changed or added?
X2 for THIS !!!

And if you feel your skills are good enough to dig into,then after checking the cables and terminals ditch the aftermarket alarm and revert
the wiring back to factory Jeep. Then check the wiring in the rubber grommets which go to both front doors. Look for broken wires.
Try to pull wire by wire as they often break inside insulation but visually look normal.
Remove both kick panels in the front. On each side there are 2 big connectors with a screw in the middle sitting one above another.
Remove and check for corrosion on terminals
 

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I assume that you had a crank, but no start. As long as the vehicle is cranking, it’s not a battery issue.
my aurora did all kinds of goofy things… the headlights would go out and come back on. The dash lights would flicker off for a half second or so. The car would die at speed. Never had a no start. New crank sensors and all the goofy went away.
my Son’s wj, did all kinds of goofy, just different. It would drive all the way to work one day (25 miles) then the next day it would die 3 times during the drive. Then it would be good for a day or two.
I’m pretty sure there is a single sensor in the Jeep system. The gm system has 2 discrete sensors. Ours on the wj would get warm and stop working.
sometimes it would throw the no crank or cam signal code, but not always.
Has not missed one beat since the new sensor.
 

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Discussion Starter · #7 ·
X2 for THIS !!!

And if you feel your skills are good enough to dig into,then after checking the cables and terminals ditch the aftermarket alarm and revert
the wiring back to factory Jeep. Then check the wiring in the rubber grommets which go to both front doors. Look for broken wires.
Try to pull wire by wire as they often break inside insulation but visually look normal.
Remove both kick panels in the front. On each side there are 2 big connectors with a screw in the middle sitting one above another.
Remove and check for corrosion on terminals
I'm probably not using the best terminology, but the engine would turn over. Just wouldn't fire. It would seem to fire on a couple cylinders, but almost like the timing was out of whack. Cleaning the terminals, terminal clamps seemed to alleviate the electrical issues, but it also won't run long enough to diagnose much. I'll check this wiring going to the doors!
 

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Discussion Starter · #8 ·
not cranking would have me look at the battery cables - both ends, the terminal clamps- TIGHT?
The positive feed to the PDC.
Do scan of the sysem post ALL codes, at least key on off trick if no scanner.
Do you have BOTH keys and used both?

Whats your skill level - comfortable with a test light and a wiring diagram ?

Was anything electrical changed or added?
Weird thing is that it's not throwing codes. I've used an OBD II scanner, and also the method of turning the ignition switch on/off to get a code to flash on the odometer. Prior to all this happening it was throwing a couple evaporative emissions codes. But over the last couple months hasn't given a single one.

Only have one factory key that will work in the ignition. Made a couple spares, but they won't start it since they don't have a chip.

I'm lucky enough my dad is good with electrical circuits, so if we had a good wiring diagram we could troubleshoot further. My personal skill level is basic at best.
 

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Discussion Starter · #9 ·
I assume that you had a crank, but no start. As long as the vehicle is cranking, it’s not a battery issue.
my aurora did all kinds of goofy things… the headlights would go out and come back on. The dash lights would flicker off for a half second or so. The car would die at speed. Never had a no start. New crank sensors and all the goofy went away.
my Son’s wj, did all kinds of goofy, just different. It would drive all the way to work one day (25 miles) then the next day it would die 3 times during the drive. Then it would be good for a day or two.
I’m pretty sure there is a single sensor in the Jeep system. The gm system has 2 discrete sensors. Ours on the wj would get warm and stop working.
sometimes it would throw the no crank or cam signal code, but not always.
Has not missed one beat since the new sensor.
Yeah, it engine would turn over but no start. Up until the last week, it's been acting like your son's WJ. I could drive it around for a while and it would be fine. Then all of a sudden it won't run for more than a couple minutes.

The '02 Ram I had acted similar to you Aurora. It ran fine, but all kinds of screwy electrical things. Like when I'd hit the turn signal, the headlights would flash, horn would blow, and the wipers would cycle. Very inconvenient to say the least.

Sounds worth replacing the cam/crank sensors before going down the PCM rabbit hole. That terrifies me.
 
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