99 PCM replace/update
#331
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From: CO
Year: 99
Model: Cherokee (XJ)
Engine: 4.0
I suppose what you're really asking is
and I do not know that. But since 1391 can be generated by
I think we're REAL close. With an otherwise normal and synced CPS signal that artifact (I believe it's coil) would seem to be the culprit. I think it's either the CPS, the distributor cap, rotor or somewhere along the harness to the ECU.
and I do not know that. But since 1391 can be generated by
I think we're REAL close. With an otherwise normal and synced CPS signal that artifact (I believe it's coil) would seem to be the culprit. I think it's either the CPS, the distributor cap, rotor or somewhere along the harness to the ECU.
by "coil" you mean "pickup coil" yes?
#332
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#333
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From: CO
Year: 99
Model: Cherokee (XJ)
Engine: 4.0
Hmm, my ignition coil is only a few months old echlin brand, replaced while on the hunt in this thread( stock ohmed good but had a crack in the insulation), the new one didnt change anything.
Is this something the scope can check? Don't want to fry it lol
Is this something the scope can check? Don't want to fry it lol
Last edited by 4x4jeepmanthing; 11-25-2019 at 10:55 AM.
#334
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You can fiddle with this with the Hantek by using the attenuator probe on the secondary coil and it should match up with the artifact in the CPS (don't be standing in a puddle of water while playing with the secondary coil).
#335
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I'm sure it's fine.
1. Check the distributor cap and rotor for any signs of arcing.
2. Folllow the CPS signal wire all the way back to the ECU to see if it has any contact with the coil supply wire.
3. Change out the CPS.
4. If the CEL remains on, cover with the aforementioned black tape.
1. Check the distributor cap and rotor for any signs of arcing.
2. Folllow the CPS signal wire all the way back to the ECU to see if it has any contact with the coil supply wire.
3. Change out the CPS.
4. If the CEL remains on, cover with the aforementioned black tape.
#336
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From: CO
Year: 99
Model: Cherokee (XJ)
Engine: 4.0
Because it appears in every set of reluctor windows, it has to be either all 6 spark plug wires (TTBOMK, impossible), scatter from the high voltage side of the coil, or perhaps contamination from the wire that signals the coil to fire (I'm away from my stuff again for the holiday, but see if the CPS wire is in the same harness as the coil signal supply wire). Since the artifact looks to be only about 7-8 volts, it can't be a direct shot from the secondary coil (which would fry everything).
You can fiddle with this with the Hantek by using the attenuator probe on the secondary coil and it should match up with the artifact in the CPS (don't be standing in a puddle of water while playing with the secondary coil).
You can fiddle with this with the Hantek by using the attenuator probe on the secondary coil and it should match up with the artifact in the CPS (don't be standing in a puddle of water while playing with the secondary coil).
im trying to dig up wiring diagram for this coil
#337
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#338
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From: CO
Year: 99
Model: Cherokee (XJ)
Engine: 4.0
I'm sure it's fine.
1. Check the distributor cap and rotor for any signs of arcing. will do!
2. Folllow the CPS signal wire all the way back to the ECU to see if it has any contact with the coil supply wire. out of two wiring harnesses I can confirm the current, which I fully gutted and reworked, has no wires touching.
3. Change out the CPS. headed to the JY to see if I can get lucky with a mopar cps, otherwise I can stop by napa on the way home.
4. If the CEL remains on, cover with the aforementioned black tape. did you one better, ive already pulled the light haha.
1. Check the distributor cap and rotor for any signs of arcing. will do!
2. Folllow the CPS signal wire all the way back to the ECU to see if it has any contact with the coil supply wire. out of two wiring harnesses I can confirm the current, which I fully gutted and reworked, has no wires touching.
3. Change out the CPS. headed to the JY to see if I can get lucky with a mopar cps, otherwise I can stop by napa on the way home.
4. If the CEL remains on, cover with the aforementioned black tape. did you one better, ive already pulled the light haha.
#340
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#345
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There is that thing where the major spikes only occur when CPS is sending 5 volt signal. Is that diagnostic of a faulty CPS? IDK, but certainly something to ponder on...