2003 Rubicon with P1391 code

rab669

New Member
Feb 11, 2019
5
Atlanta
I am at a loss as is my mechanic

Golen Stoker 4.6 with about 8,000 miles.
Had a bad exhaust gasket and was misfiring on 2 and 5. that was fixed and jeep ran fine for 6 months
Then I had a broken value spring on Cyl 5 - Repaired that

Next at about 3,000 rpm the jeep would throw misfire on Cyl 5 and go into Limp Mode. Turn key off then on and jeep would run fine

Mechanic has had it about 2 months and we are all running out of suggestions.

1: Fuel Injectors returned to manufacturer for cleaning and inline filters
2: Cam Position sensor swapped from a jeep that was running fine - other jeep runs fine with my CPS
3: Crank Sensor swapped from a jeep that was running fine - other jeep runs fine with my CKS
4: Ignition Coil replaced with 2 different ones
5: Plugs replaced
6: All wiring inspected and tested by Jeep mechanic
7: Ignition Timing set (off by 1 degree)
8: Fuel Timing checked
9: Fuel Pressure tested OK
10 PCM sent for testing and repair. Shop claimed some capacitors were bad but said the 3 coil firing systems were fine. Charged about 350 to fix "Something" but problem remains. Claims PCM tests fine and issue is wiring downstream

Odd thing - When this started it would throw a code for Cyl 5 misfire then go into limp mode. This is the same Cyl that had the broken value spring.
After the PCM rebuild it now throws the P1391 (Intermittent Cam and Crank Sensor connectivity)
Thinking next I will purchase another PCM to rule out the repair performed on original PCM


Currently Jeep starts fine but if you drive a mile or so it throws the P1391 then goes into limp mode.

Any other suggestions would be appreciated
 
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Chris

Administrator
Staff Member
Sep 28, 2015
36,262
Salem, Oregon
If it was me, I'd seriously think about purchasing a PCM from another vehicle that is known to work. I'd want to rule that out, since it sounds like the work they performed on the PCM was questionable at best.

It might not be PCM related, but it doesn't hurt to have another spare one on hand.

What brands of replacement crank and camshaft sensors did you replace them with?
 
OP
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rab669

New Member
Feb 11, 2019
5
Atlanta
Not sure about the brand of sensors. We have a jeep performance shop in town and the owner has taken the challenge to figure this out. He took the sensors of his own personal jeep and swapped them with mine. Mine run fine in his jeep

The computer was repaired by Auto Computer Specialist in Plantation FLA and there after sale support just pain sucks. These guys are not helpful.

Any suggestions on a better place to purchase another PCM. I was thinking about ProTech Auto systems or Car Computer Exchange. I also my try and find someone with the same jeep and just try their PCM in my jeep.
 
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rab669

New Member
Feb 11, 2019
5
Atlanta
Also do you know if I can just take the same computer out of another similar 2003 Rubicon and test it in my Jeep or do I have to first have the Vin and Mileage updated?
 
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rab669

New Member
Feb 11, 2019
5
Atlanta
Spoke to module gods and they feel pretty certain that the software on the pcm is corrupt. Going to sent to them to test it and see what they say
 
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rab669

New Member
Feb 11, 2019
5
Atlanta
Well they told the ecu module was bad and sold me a new module built from the ground up. Not cheap. And the problem still persists. Same proble with the new module. Jeep throws a P1391 ( loss of cam or crank sensor) after running about 5 minutes and eventually throws a misfire on cylinder 3 or 5. Everything had already been replaced and wiring tested. Maybe I’ll just part this out and move on. Frustrating. Been going on for 4 months and 2 different shops, and 2 ecu companies later- no change