Please help: Limp Home mode/P2138 -

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Old 06-16-2017, 09:13 AM   #1
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Join Date: Jun 2017
Location: SC
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Default Please help: Limp Home mode/P2138

4.0L 2008 Coupe, no mods. I've had this car for almost 10 years, bought it with 63 miles on it. Two weeks ago the "limp-home" wrench showed up. Threw it into neutral, restarted the engine, wrench went away. Wrench came back after about 5 miles, now with a MIL. Checked the code with my scan tool and all it had was a P2138: throttle/pedal position sensor voltage error. Replaced the TPS, cleared the code, disconnected the battery to reset the PCM, and let it relearn idle. Drove fine to and from work for three days, then same wrench and MIL code. Replaced the pedal position sensor, reset PCM again. Same thing. Drove for about 15 miles and wrench/MIL came back right as I coasted into the parking lot. I'm thinking either it's a wiring problem (corrosion, short, etc) or maybe PCM that's on its way out. It's weird that it drives fine for a bit after every idle-relearn procedure/PCM reset (it seems not intermittent enough to be a wiring issue, but I could be wrong). OR it could be the entire throttle body, but I don't know why it's throwing P2138. Sorry for the long post; any thoughts/help would be greatly appreciated!
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Old 10-11-2017, 01:02 PM   #2
Join Date: Oct 2017
Location: texas
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I'm dealing with the same issue. I have a 4.0L 2008 Coupe with no mods with 130,000 miles on it.

I was driving my car on the freeway and it fell into limp mode (wrench light on). I was able to safely drive off thinking my transmission went out. After, I took it to a mechanic and they said it was related to my throttle body and would charge me $900 to replace and reprogram my computer. I decided to just replace it my self and did. I did the disconnect battery relearn procedure but still had issues. I then took it to the dealer ship and they said aftermarkets sometimes don't work. I replaced with another throttle body and i got the same issue. I then replaced the pedal position sensor and did the relearn procedure again. This minimized the issue a lot but did not completely fix the issue. My car will now go into limp mode after a day or two of driving and will go away after I restart my car. I've been driving it like this for two weeks. So after all of this i don't know what is going on. Why would replacing my pedal position sensor help but not completely fix the problem. Why does restarting my car turn the wrench light back off and back to running normal for awhile . Why can my car run great for two days then fall back into limp mode?

Let me know if replacing your whole throttle body worked for you or if you find any fix. Thanks
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Old 10-11-2017, 02:52 PM   #3
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Join Date: Jun 2017
Location: SC
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Default The answer will frustrate you

After messing around with the pedal position sensor for way too long I decided to take a break for a week and then reattack with fresh eyes. As soon as I popped the hood I saw the problem. It ended up being a broken wire on the throttle position sensor harness. It was the grey one; the plastic sheath had that white spot you can see on wires where the interior wire has broken at a sharp angle inside of the plastic sheathing. I confirmed by straightening the wire out and taping it to a wooden splint, which made the wrench mode permanent, no longer intermittent. I used wire strippers to open it up and sure enough; broken wire. A simple re-solder job later, no limp mode. I would take an extra-close look at your wires again; hopefully the problem is close to your sensor like mine was. I feel bad that you’ve spent so much $$ already but the best lessons are sometimes the most expensive :/. Hope this helped; good luck!!
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