Cam sensor, crank sensor or both?

matkal

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‘04 4.0, this is what the code reader comes up with and when I Google cps for my TJ both come up. Which one are the codes referring to ? Also, what is a good brand for replacements as Mopar are discontinued?
 
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It's more common for the crankshaft position sensor to fail. Avoid store brands and if you have the 4.0 engine make sure to get one to match your transmission type, automatic or manual.
 
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It's more common for the crankshaft position sensor to fail. Avoid store brands and if you have the 4.0 engine make sure to get one to match your transmission type, automatic or manual.

I've got both ( crank and cam, both brands) in my cart at Rock Auto, Delphi and NKS(?) I'll be ordering whichever is recommended.
 
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I've got both ( crank and cam, both brands) in my cart at Rock Auto, Delphi and NKS(?) I'll be ordering whichever is recommended.
Delphi, NTK, Mopar, or Standard Motor Products would all be fine. Personally I'd go for Mopar first followed by NTK as my first two choices. Again make sure it matches your transmission choice.
 
Matkal:

I don't know how helpful this is without a DRB III or oscilloscope at your disposal, but the Powertrain Diagnostic Procedures Manual lists possible causes and diagnostic tests for each code. There is a 2002 manual in the references section here, and it should be the same as your 2004 (they both use the JTEC+ PCM). You can find it here. One of your codes is on pdf page 131 and the other is on pdf page 191. Here are the official descriptions and set conditions for those codes:
  1. P0340 is "No cam signal at PCM" and the set description is "At least 5 seconds have elapsed with Crankshaft Position Sensor signals present but no Camshaft Position Sensor signal."
  2. P1391 is "Intermittent loss of CMP or CKP" and the set description is "When the failure counter reaches 20 for 2 consecutive trips."
Reading that information, I would start with P0340 because P1391 would trigger only after loss of signal on two consecutive trips. That means that you had an intermittent problem for a while. And then the P0340 completely stopped the engine. So, my initial theory would be that you had a crank sensor signal issue that started as intermittent and then failed completely.

Hope that helps!
 
It's worth checking the wiring on the pigtail of both the crank & cam sensors. That insulation tends to pull back and for some reason the wires are always twisted there and you can easily have a short at the sensor.
 
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Matkal:

I don't know how helpful this is without a DRB III or oscilloscope at your disposal, but the Powertrain Diagnostic Procedures Manual lists possible causes and diagnostic tests for each code. There is a 2002 manual in the references section here, and it should be the same as your 2004 (they both use the JTEC+ PCM). You can find it here. One of your codes is on pdf page 131 and the other is on pdf page 191. Here are the official descriptions and set conditions for those codes:
  1. P0340 is "No cam signal at PCM" and the set description is "At least 5 seconds have elapsed with Crankshaft Position Sensor signals present but no Camshaft Position Sensor signal."
  2. P1391 is "Intermittent loss of CMP or CKP" and the set description is "When the failure counter reaches 20 for 2 consecutive trips."
Reading that information, I would start with P0340 because P1391 would trigger only after loss of signal on two consecutive trips. That means that you had an intermittent problem for a while. And then the P0340 completely stopped the engine. So, my initial theory would be that you had a crank sensor signal issue that started as intermittent and then failed completely.

Hope that helps!

Thank you for looking that up. 👍🏻
 
It's worth checking the wiring on the pigtail of both the crank & cam sensors. That insulation tends to pull back and for some reason the wires are always twisted there and you can easily have a short at the sensor.

I’ll add that to my list.
 
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