NEED HELP PLEASE P1391 Trouble Code - JeepForum.com

 
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post #1 of 5 Old 03-25-2012, 04:24 PM Thread Starter
Sandfreak8
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NEED HELP PLEASE P1391 Trouble Code

Hello I have 1998 Jeep Cherokee Sport 4.7L Stroker That I keep getting a P1391 Trouble code. I have replaced the Crank Position Sensor, Re Indexed the Distributor same results. The Engine starts up and runs fine just keeps setting this code and preventing me from getting an emissions test. Any Help will be greatly appreciated.

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post #2 of 5 Old 03-25-2012, 04:43 PM
tjwalker
It's the crank sensor!
 
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P1391 is intermittent loss of the "crankshaft position sensor" signal OR the "camshaft position sensor" signal.

Any symptoms??

As you have replaced the crank sensor and it hasn't resolved, time for a new cam sensor.

Good luck and keep us updated!

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post #3 of 5 Old 03-26-2012, 07:59 AM Thread Starter
Sandfreak8
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I have replaced the distributor i guess it is possible that the cam Position Sensor in the distributor is defective. The Jeep has no symptoms it starts and runs fine, that is why I am at such a loss.
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post #4 of 5 Old 03-26-2012, 09:40 AM
tjwalker
It's the crank sensor!
 
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Quote:
Originally Posted by Sandfreak8 View Post
I have replaced the distributor i guess it is possible that the cam Position Sensor in the distributor is defective. The Jeep has no symptoms it starts and runs fine, that is why I am at such a loss.
First, I would clear the codes and at the same time, I'd clean the connector for the cam sensor with a thorough spray of electrical contact cleaner and then add a dab of dielectric grease to the connector and reconnect.

If the same code returns after that, I'd replace the cam sensor, even if you have no symptoms. There still could be an issue that isn't bad enough for you to sense.

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #5 of 5 Old 03-26-2012, 09:41 AM
CJ7-Tim
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P1391 (M)Intermittent Loss of CMP or CKP. Loss of the Cam Position Sensor or Crank Position sensor has occurred.

Several recent threads have been posted by Cherokee owners that have had issues with random CMP and CKP/CPS codes and some starting or running issues. In these threads a new generic CPS from Advance/IdiotZone/O'Reilly's did not resolve the issues.

What made the difference, was installation of a genuine Jeep CPS from the dealership. Cheap sensors can be not quite the correct size or can be slightly out of specification, enough so that the engine doesn't run right, despite the new parts called for by diagnostic testing.

Cheap parts are cheap for a reason.

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