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Old 10-06-2011, 04:22 PM   #1
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Throwing codes P0340 and P1391

I'm having the same problem as a lot of you I guess. My Jeep would start fine, but then after a little while of driving or idling it would sputter then shut off! Even after that there was NO Check Engine Light that came on. I already replaced the plugs and the Throttle Position Sensor since that is what I thought it would be by searching this forum... but then the CEL cam on and it threw those two codes. I searched here and found out that P0340 was Camshaft Position Sensor, so I guess I'll have to replace that. On the sheet that shows me what P1391 is, I still can't figure out what it means.

Definition: CMP or CKP signal intermittent condition
Explanation: The ECM detected the actual CMP position disagreed with the expected CMP level
Probable cause: 1. Timing belt or chain stretched or jumped. 2. Defective CMP sensor

What is CMP? What is CKP? My guess is Camshaft and Crankshaft? So by replacing the Cam Pos Sensor, this will fix my P1391?

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Old 10-06-2011, 10:18 PM   #2
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You are correct CMP = cam position, CKP crank position. You would need to find a scanner of some sort that would allow access to view the PID data and see which reference is scewed or missing

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Old 10-07-2011, 09:12 AM   #3
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Thanks! Well after the TPS didn't fix the problem but was able to take me to VatoZone, I had them pull the codes for me. It was either one of those problems that I listed before. I just bought them both and see which fixed it. I installed the CMP first and then the CKP. I had no idea it would be such a PITA to take off and install the CKP!!! I am just going to leave them both on and not fool with testing which one was the culprit, call me lazy. So I'm under $140, but at least I have three new sensors and new plugs. I'm ok with that.
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Old 10-08-2011, 09:31 AM   #4
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what yr is your jeep? i am having the same problem with my 1999. will start just fine and drive but out of the blue it just dies...sometimes for just a second and the longest was for about 10 minutes before it would start again on the side of the road. no check engine light..put it on one of those homeowner obd2 scanners and no codes came up..going to take it to the the shop and have them put it on the scope..did replacing those sensors cure your problem
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Old 10-09-2011, 07:05 AM   #5
Join Date: Aug 2011
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I have the exact same problem with my jeep (2002 TJ) and it only occurs in cold weather... If it's in the 40's it'll start sputtering on start. If it's any colder it won't start at all and throw the codes. I have to leave the key engaged so all the electronics are on for 5 mins and then it will start up and sputter but all the problems go away when it heats up... Replaced the sensors and it behave slightly better now.
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