Am I headed down the right path?


RangerZ21i

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Oct 24, 2017
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91
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Southeast LA
Yesterday leaving the neighborhood my CEL illuminated, the engine started to sputter and eventually died. After a few minutes the engine would start but die as soon as it started. I eventually got it running and made it home, sputtering the entire way. Scan gave me codes P0121, P0455 and P0442. P0442 and P0455 are both related to the evap emissions system?. Because of P0121 and out of weekend desperation and I replaced the TPS with an Orielly part, cleared the codes and saw no change in the way the vehicle was running. (Mopar TPS is on order). CEL on again immediatly after Orielly TPS change, P1297 which is a MAP code. Decided to clear the code and try one more time, engine ran the same and this time picked up P0340 (camshaft pos. sens) and P1296 (no 5v to MAP sensor).

Is it likely the Mopar TPS will fix the problem? Should I replace the MAP sensor? What else should I do to help diagnose ?
 

Mall'er

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May 3, 2021
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I suspect not. I believe all of those sensors share a 5v power. I expect you have a damaged wire in the harness. When the engine is running, start wriggling the wire harness, and see if you have a change. You can also probe the sensors to see if you have the needed 5v on the power side.
 

CharlesHS

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Doubtful... it will help.
Sounds as though you may have a an intermittent short of the 5V reference for your sensors.
As posted above... check the wiring harness for your sensors...
I would check the wiring at the O2 sensors... shorts down at the harness are some what common.
Check in the forum TJ Resources section where you can download PDFs of the FSM for your year TJ.
Section 8W will have the wiring colors, pin outs and connector numbers to assist in tracing the wiring harness.

 
OP
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RangerZ21i

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Oct 24, 2017
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Southeast LA
I checked power at the plug of MAP sensor prior to starting the engine and had 5v, checked again while and after running and had trouble finding 5v again, eventually did. Wiggling wires did not seem to help while the engine was running. Could this be a ground issue associated with the grounding strap from the engine to to firewall?
 

Mall'er

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The ground (returns) for those sensors go back to the PCM. Then the PCM is grounded to the block.
When you check the voltage, use the return line as your ground. If that return line is flaky you will get intermittent voltage also.

The only reason I suggest this path is that you are getting codes for are on the same PCM circuit. Have you tried your old TPS to see if the new codes go away?

Cleaning your grounds is always a good idea, they can cause all sorts of strange conditions. I am not sure, but I think the PCM block ground is by the oil pressure switch.
 
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RangerZ21i

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Oct 24, 2017
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Southeast LA
I am going to get back to electrical testing later today. I cleared the codes and the one that keeps returning is actually P1297 which I think is a MAP problem associated pressure differential atmosphere to inside the manifold. That said while I had the breather off the throttle body I decided to clean it and the throttle valve. When I sprayed cleaner in the TB I could see cleaner coming out of the TB onto the intake manifold. I don't think this is supposed to happen as if the cleaner can get out the air can get in. Correct? Is it possible I have a bad TB gasket? or something leaking vacuum in the TB area??
 

Mall'er

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Where was the cleaner spraying from the TB? If you had the map disconnected, it is a direct line from the inside of the TB to the outside where the MAP sensor plugs in.

If you do decide to replace the TB gasket, they are about 3 bucks or so at your local auto parts store. You will only torque the TB down at 90 INCH/lbs. If you do 90 FOOT/lbs, you will not be happy.
 
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RangerZ21i

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Oct 24, 2017
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91
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Southeast LA
Where was the cleaner spraying from the TB? If you had the map disconnected, it is a direct line from the inside of the TB to the outside where the MAP sensor plugs in.

If you do decide to replace the TB gasket, they are about 3 bucks or so at your local auto parts store. You will only torque the TB down at 90 INCH/lbs. If you do 90 FOOT/lbs, you will not be happy.
MAP sensor was still installed on the manifold while I was spraying. I could not tell exactly where it came from but definitely from the TB. I am going to change the TB gasket and put a new OEM TPS and cross my fingers.
 
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RangerZ21i

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Oct 24, 2017
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Southeast LA
Still need advice.
I removed the throttle body and cleaned body and sensors, installed Mopar TPS. When the engine runs it runs better BUT for the most part I am having the same sputtering and dying issues. I am getting still getting code P1297 but also getting P0155 (O2 sensor bank 2 sens 1). What do I do next? Change 02 sensor?