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Old 07-18-2014, 02:19 PM   #1
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P0122 - issue not what you think

Help! Ghost in the 2.5L machine!?!

So I've been getting a P0122 code and a MIL, and have gone through the following troubleshooting steps:

  • verified properly functioning TPS - getting 5.12V reference voltage at sensor, getting signal output within spec at all throttle positions with no dead spots in the range
  • verified ground continuity at the sensor, and as far back in the wiring harness as I can go
  • replaced connector and wiring pigtails
  • cleaned battery terminals and verified voltage into ECM
  • replaced the TPS twice just to make sure (thanks warranty!)
  • removed and cleaned the throttle body, MAP sensor pickup tube, IAC housing and sensor
  • lubricated throttle cable (this wasn't an issue)
  • had a professional mechanic friend run a diagnostic scan to get some data monitoring - ECM showing good voltage input from the TPS
The damn thing is still throwing the code, and I still get a hiccup in acceleration - worse between 1200-2200 rpm, but still there at full throttle.


What am I missing?!?

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Old 07-19-2014, 12:00 AM   #2
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Quote:
Originally Posted by DermJeep View Post
Help! Ghost in the 2.5L machine!?!

So I've been getting a P0122 code and a MIL, and have gone through the following troubleshooting steps:

  • verified properly functioning TPS - getting 5.12V reference voltage at sensor, getting signal output within spec at all throttle positions with no dead spots in the range
  • verified ground continuity at the sensor, and as far back in the wiring harness as I can go
  • replaced connector and wiring pigtails
  • cleaned battery terminals and verified voltage into ECM
  • replaced the TPS twice just to make sure (thanks warranty!)
  • removed and cleaned the throttle body, MAP sensor pickup tube, IAC housing and sensor
  • lubricated throttle cable (this wasn't an issue)
  • had a professional mechanic friend run a diagnostic scan to get some data monitoring - ECM showing good voltage input from the TPS
The damn thing is still throwing the code, and I still get a hiccup in acceleration - worse between 1200-2200 rpm, but still there at full throttle.


What am I missing?!?


i got the same thing that you got except mine threw the code PO123 but i experience the same symptoms you are i would hiccup at exactly 2000rpm, my solution was the clockspring behind my steering wheel that connects to your airbag and horn and cruise (if you have it). remove the lower steering column behind the steering wheel held together by two screws, once you remove the lower column it should look like this:


remove that white plug dont touch the yellow one thats your airbag, once that white plug is disconnected be aware that you cannnot use your horn or cruise control. take your jeep out for a spin if it is back to normal then you need a new clockspring

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Old 07-19-2014, 07:42 AM   #3
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@Jassio- thanks, I'll follow up today and post results.
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Old 07-20-2014, 09:22 AM   #4
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&@;&#%*|„!!!!

Disconnected the clockspring, and that took care of the code error. I'll replace it just to get an inspection to pass.

But, the acceleration stumble issues haven't disappeared altogether. I'm going back to basics: check fuel pressure, distributor, spark plugs and wires, vacuum system. What else is there if all airside issues check out?!?

Beyond that, all I can think of is a PCM reflash. What kind of POS diagnostic system can't pick up a misfiring issue and relies on a tiny ribbon cable to maintain electrical grounding?
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Old 07-20-2014, 02:42 PM   #5
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Problem found! I removed all the cable shrouding for the entire wiring harness, and sure enough, I found a spot in the ground wire where the insulation was skinned!

It was right near a splice from the PO or PO's mechanic. OBD-II scanner confirmed consistent TPS input and engine load once I re-did the wiring conneciton.

Clockspring still needs to be replaced, but now I can drive it without feeling like a rodeo cowboy. I hate electrical issues.
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