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Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > 96 ZJ Just stops running.

Rockridge 4WD IS Taking Zone Offroad Suspension Lift Kits JEEP Gear Change Packages From ROCKRIDGE 4WD. We Are DIFFIron Cross Customer JK and TJ Wrangler Bumpers now at ROCK

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Unread 09-02-2013, 02:07 PM   #16
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 4,222
Quote:
Originally Posted by ZeeJay1997 View Post
lol, pencil neck geeks!
It's OK for me to say that because I was one of them, many years ago. You know the type.... a TI calculator on my belt, a pencil behind my ear and a stupid grin on my face. I just couldnt bring myself to wear a pocket protector, though. I have my limits....

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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."

Stalling? Work through Zeejay's list
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Unread 09-02-2013, 05:41 PM   #17
cletus93
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Mine did the same thing try the coil pack thats what mine was
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Unread 09-06-2013, 04:19 AM   #18
Speedymcracer01
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It sounds like what mine did when the o2 sensor was pulled loose by a down limb after the drive shaft rubbed it down to wires it kept arching causing my pcm to temporarily loose power when mine lost power it would do it so fast i just felt like the transmission kicking and loosing drive until it got caught on the drive shaft which blew the main power supply fuse to the pcm in the pdc. The problem your having might not be a loose o2 sensor arching. But it sounds alot similiar. But mine only died when it would blow the fuse in the pdc though. But i wouldn't rule out it being a sensor shorting out on something temporarily disabling your pcm killing the vehicle like it did mine. I traced all my wires from the pdc to the pcm then from there to the sensors the wires ran to. It's not that easy if you still have wire covers wrapping the wires but its not all that hard either. If all that checks out good then your pcm could be getting ready to give out on you
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Unread 09-09-2013, 11:48 AM   #19
MeWJWifeZJ
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1996 ZJ 
 
Join Date: Sep 2008
Location: Richfield, Minnesota
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Quote:
Originally Posted by ZeeJay1997 View Post
here's an afterthought, if the crank sensor signal is absent, the PCM doesnt send the relay grounds.

It will not crank or run without crank sensor signal.
It will run but not crank without cam sensor signal

So the as the code suggests, and intermittent crank sensor signal is suspect. Since you have changed the sensor already, it would be a good idea to pull the black connector off the PCM and check pin 18. it may be pushed back. The sensor ground is furnished from the PCM on pin 4. it splices in the main engine harness near the injector wiring breakout.

Also, remove the TPS connector and turn the key on. Check for 5V between the two outside sockets on the connector.
Took off the covering from the entire wiring harness from the back of the engine to the grounds on the right cylinder head, also took the covering off the wiring from the PCM to the back of the engine block. Spent 3 hours inspecting each wire for burn marks, chafing, broken wires etc and found nothing. There are several factory splices that appear to be connected with a heat shrink tubing but I did not cut those apart. Pin 18 is right at the end of the connector just like every other connector and is just as tight as the others as well. Pin 4 is clean an in place as well.

Does the computer have to "re-learn" after it's disconnected? The reason I ask is because after re-connecting all the wiring after sealing it back up, I still had no CEL on the dash and no response from the Fuel or voltage gauges, the volt gauge wouldnt even read battery voltage. The red security light on the top of the dash remained lit for about 30 seconds after turning the key on.

Once it started, it died almost immediately. Restarted several times and once it ran for 22 minutes before dying again without warning. The ASD relay clicks when it dies but swapping the relays doesnt change anything. IF it dies and the connection is lost for an extended amount of time, the PDC box relays all start clicking as the make or lose connections.

I'm beginning to hate this truck. My Wife already hates me for buying it. Other ideas?
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Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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Unread 09-10-2013, 02:32 AM   #20
Speedymcracer01
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The computer doesn't relearn. It is programmed from the factory to run the vehicle a certain way for maximum fuel economy,and have the best emission quality as possible determined by what information the sensors are feeding it. As the engine runs the sensors tell the computer how everything is working with small amounts of volts. The computer does have factory default settings. Say the o2 isn't sending any volt readings to the computer telling it the emissions are good, and the current fuel air mixture is where it needs to be. The factory default setting is activated supplying the engine with a constant fuel supply thats not regulated by the computer like it normally is for emission control since it has no idea what the emissions are any more. This willcause it to run rich
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Unread 09-10-2013, 05:28 AM   #21
ZeeJay1997
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So you're back to square one?
You're probably looking at a bad PCM.


for the record: The PCM learns fuel strategies for the closed loop mode.
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Unread 09-11-2013, 04:30 PM   #22
MeWJWifeZJ
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1996 ZJ 
 
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Location: Richfield, Minnesota
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New PCM, same result. Truck stalls and wipes all stored computer info including codes. PDC relays all start clicking and Voltmeter and Fuel gauge reset to their "rest" position as if the key was off until the relays click back to life and make connection. Switched all relays around to check functionality, all check good. Grrrr.....
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Praise to a Child is like Sunlight to Flowers

Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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Unread 09-11-2013, 04:43 PM   #23
ZeeJay1997
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your suspects are crank sensor, o2 sensor, pcm battery and ground inputs.

that's all i know of that will wipe the codes other than internal problems.
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Unread 09-11-2013, 08:00 PM   #24
craddock01
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1996 ZJ 
 
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All right heres a suspect to add to add to your list my relays were causing all of the above probs because of a nice layer of gray corrosion on the prongs. Cleaned them up Varoom! Never had a prob since.

(Fuel pump relay was the culprit but I went thru and cleaned all of the relays and fuses inside. Got lots of Humidity around here)

Oh yeah also add I swapped my relays too seemed like they were good . The corrosion causing low/no voltage to fuel pump intermittently
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Unread 09-11-2013, 08:41 PM   #25
ZeeJay1997
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Quote:
Originally Posted by craddock01 View Post
All right heres a suspect to add to add to your list my relays were causing all of the above probs because of a nice layer of gray corrosion on the prongs. Cleaned them up Varoom! Never had a prob since. (



Quote:
Originally Posted by MeWJWifeZJ View Post
So tonight I completely disassembled the PDC and cleaned each terminal as well as cleaned off each termial on every relay, and fuse with emery cloth.
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Unread 09-11-2013, 11:51 PM   #26
Speedymcracer01
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Quote:
Originally Posted by craddock01 View Post
All right heres a suspect to add to add to your list my relays were causing all of the above probs because of a nice layer of gray corrosion on the prongs. Cleaned them up Varoom! Never had a prob since.

(Fuel pump relay was the culprit but I went thru and cleaned all of the relays and fuses inside. Got lots of Humidity around here)

Oh yeah also add I swapped my relays too seemed like they were good . The corrosion causing low/no voltage to fuel pump intermittently
How would the fuel pump relay cause the pcm the erase codes
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Unread 09-11-2013, 11:58 PM   #27
Speedymcracer01
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When you cleaned the pdc did you check the connection from the pcm fuse "make sure the fuse didn't feel kinda loose in the fuse compartment". If the pcm is erasing codes before it tells you the problem then its sounds like a power supply issue. Just wondering have you checked all you power supply wires from the battery to the pdc to the pcm?
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Unread 09-12-2013, 11:22 AM   #28
MeWJWifeZJ
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1996 ZJ 
 
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Location: Richfield, Minnesota
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When I cleaned the PDC I did disconnect the positive power supply and it was tight when I removed the connection. That cable end was also cleaned. If I keep my foot on the gas in park, i can keep it running by giving it more gas when the Jeep wants to die because it recovers within 1 - 2 seconds usually. Even when it stumbles and doesnt die because I have the RPM's at 2000 - 2500, it still wipes the computer. If i can keep it going without it trying to stall, it'll pop code P1391 but as soon as it wants to stall it erases that code. If I have time to view a freeze frame on my cheap scanner, the 1st O2 is in open loop, the second says CL-Fault, the operating temp is accurate (Matches the gauge on the instrument panel) and teh RPM matches.
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Praise to a Child is like Sunlight to Flowers

Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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Unread 09-12-2013, 07:44 PM   #29
ZeeJay1997
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try starting it, then disconnect the cam sensor. it will use default fuel time and go into open loop mode.

if this doesnt help, you need to reassess the crank sensor.
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Unread 09-12-2013, 07:57 PM   #30
MeWJWifeZJ
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1996 ZJ 
 
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Once the cam sensor is disconnected, will it die if the cam sensor is bad? The cam sensor was new about 2 months ago because it did fail and threw a code and would crank all day but not fire.
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Praise to a Child is like Sunlight to Flowers

Traded away the WJ to get a commuter

We finally got another Jeep after 5 years without. Too bad it's ALL stock.
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