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Good Afternoon everyone! first time poster.. Codes pulled (P0340, P1391)
I have a 2004 Jeep Wrangler with a 4.0L I6. Jeep starts and idles beautifully but once I apply power it starts to back fire, ignition coils all shut down and stall out. I came across Scanner Danners youtube in the process of research which has helped me diagnose and dive deeper into these pull down hall effect sensors that Chrysler’s use.
So here’s my question, I purchased an oscilloscope to read the signals for both the CKS and CPS and have found that the CPS intermittently loses signal. I sometimes have no 5V signal when the sensors plugged in and once unplugged it goes to 5V which tells me the sensor is bad. I just replaced the camshaft sensor with a NEW NAPA Echlin brand and it goes back to 0V when plugged in.. I’m at a loss with what to test now, if anyone has guidance or advice please that would be greatly needed to get this unit back on the road!
I just replaced the camshaft sensor with a NEW NAPA Echlin brand and it goes back to 0V when plugged in.. I’m at a loss with what to test now, if anyone has guidance or advice please that would be greatly needed to get this unit back on the road!
Have you run the engine after you replaced the sensor? :huh: Does the sensor signal remain at 0V with the engine idling?
The camshaft sensor tone wheel is just a 180 degree shutter, which means you have a decent chance of the camshaft sensor pointing at the 'low' portion of the tone wheel at any given time with the engine stopped. It may be that the sensor is reporting 0V because it's doing its job.
I did have it running and still was reading 0V, also tested with the sensor off the dummy shaft and used a razor blade in front of the magnet and was still reading nothing.. I just checked resistance between the PCM and the signal wire and i’m getting 1.9kohms! Looks like I have an intermittent open in the signal wire! correct me if i’m wrong? i’m fairly new to all this lol.
I just checked resistance between the PCM and the signal wire and i’m getting 1.9kohms!
How was this reading obtained? PCM and CMP unplugged probing the signal wire terminals on each end? 1.9K doesn't sound bad enough to prevent you seeing a 0-5V square wave at the sensor.
Back probed the signal wire with the PCM harness still connected.. I had the cam sensor connectors unplugged during this test, that’s probably why I had a higher resistance was due to the PCM being connected..
Back probed the signal wire with the PCM harness still connected.. I had the cam sensor connectors unplugged during this test, that’s probably why I had a higher resistance was due to the PCM being connected..
Best to re-do the test with the PCM unplugged to be sure. Or personally I'd just ground the signal wire thru' the mA shunt of my DMM KOEO. Then tap it to ground a few times to see if it sets a P0320 :silly:
Interestingly the ohm reading you got is about double the PCMs internal signal circuit resistance. So I'm wondering if you'd maybe backprobed another signal wire and measured resistance thru' the PCM??
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