Code p1391

Keith1138

Keith1138

Well-Known Member
Joined
Nov 18, 2015
Location
Harrisburg NC
After fixing the rear axle in my 2000 Jeep Cherokee I went to pull it out of the garage and it had an extremely rough idle and it would die. It originally threw the code p1391. After looking it up on the inerwebs I found it can be either caused by the crankshaft or cam shaft position sensors going bad. So I ran out and grabbed a camshaft position sensor since the crankshaft was a mopar one I installed a few years ago. This did not solve the problem. I did confirm the cam shaft is in sync by setting the engine at TDC and the holes on the cam shaft sensor shaft thing (The thing the distributor would mount to) aline.

So I broke out the multimeter and tested to make sure everything was getting its 5 volt feed along with a good ground and the 5 volt from the computer through the signal wire. I tested the cam, crankshaft and tps since they are on the same circuit for the computer. Everything checked out. So I decided to replace the mopar crankshaft position sensor with a parts house one. Just as a temporary solution. This did not fix the issue instead it started throwing a p0122. Tps circuit low code.

At this point I'm lost so I decided to clean every single ground. With a wire wheel in a drill. I cleaned the two under the ac compressor, the ribbon, and the one by the battery. Still no change in the idle or codes. So I continue to do some research I found a similar thread and the cause was his tcu was coroaded. This morning I pulled my tcu and cleaned the connecter with electrical parts cleaner. I also cleaner a ground that was under the dash. The jeep ran the same with the tcu plugged in and unplugged in. And the same after it was cleaned. Then I unplugged the ECU/PCM and cleaned the plugs. The issue still presist with both codes being thrown.

At this point I'm leaning towards the pcm or tcm being bad. Any advice or anything else to check?
 
a stretched timing chain or jumped chain will throw this code. I have attached a 2000 xj service manual. the pin out is there in the schematics. I would back prob the harness and ohm each circuit. You may have a sync issue between crank/cam sensors also.
 

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Keith1138 said:
After fixing the rear axle in my 2000 Jeep Cherokee I went to pull it out of the garage and it had an extremely rough idle and it would die. It originally threw the code p1391. After looking it up on the inerwebs I found it can be either caused by the crankshaft or cam shaft position sensors going bad. So I ran out and grabbed a camshaft position sensor since the crankshaft was a mopar one I installed a few years ago. This did not solve the problem. I did confirm the cam shaft is in sync by setting the engine at TDC and the holes on the cam shaft sensor shaft thing (The thing the distributor would mount to) aline.

So I broke out the multimeter and tested to make sure everything was getting its 5 volt feed along with a good ground and the 5 volt from the computer through the signal wire. I tested the cam, crankshaft and tps since they are on the same circuit for the computer. Everything checked out. So I decided to replace the mopar crankshaft position sensor with a parts house one. Just as a temporary solution. This did not fix the issue instead it started throwing a p0122. Tps circuit low code.

At this point I'm lost so I decided to clean every single ground. With a wire wheel in a drill. I cleaned the two under the ac compressor, the ribbon, and the one by the battery. Still no change in the idle or codes. So I continue to do some research I found a similar thread and the cause was his tcu was coroaded. This morning I pulled my tcu and cleaned the connecter with electrical parts cleaner. I also cleaner a ground that was under the dash. The jeep ran the same with the tcu plugged in and unplugged in. And the same after it was cleaned. Then I unplugged the ECU/PCM and cleaned the plugs. The issue still presist with both codes being thrown.

At this point I'm leaning towards the pcm or tcm being bad. Any advice or anything else to check?
Click to expand...
You said you replaced the cam sensor. Is it a one piece deal with synchro, or two piece? If it's two piece, might want to try replacing the synchro.
 
fordwheelinman said:
You said you replaced the cam sensor. Is it a one piece deal with synchro, or two piece? If it's two piece, might want to try replacing the synchro.
Click to expand...
It was a two piece.

So after spending many days dealing with the issue I found a signal wire grounding out from the crank position sensor. Along with the coil rail was dying. I figure these issues compound to cause many weird symptoms because the two were not connected. After fixing the wire and replacing the coil rail everything seems to be solved.
 
Keith1138 said:
It was a two piece.

So after spending many days dealing with the issue I found a signal wire grounding out from the crank position sensor. Along with the coil rail was dying. I figure these issues compound to cause many weird symptoms because the two were not connected. After fixing the wire and replacing the coil rail everything seems to be solved.
Click to expand...
Random wiring issues is what made me split the harness open on my 96 Dakota and fuse everything powered by the ASD relay.
 
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