Can't Shake Limp Mode -- No CEL (1 Viewer)

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So my limp mode saga continues. In early December, my newish-to-me 05LC100 with 156K threw a P2118 code and went into limp mode. The ETCS fuse was intact, so I towed it to my experienced cruiser mechanic. The wiring all seemed to check out, but the motor on the throttle body was giving bad readings so we replaced the throttle body.

After installing a new OEM throttle body, P2118 and limp mode returned. Suspecting a problem in the ECM, I shipped it off to G7 Computers for a repair. They reported finding a hardware problem in the ECM and repairing it.

So we plugged the newly repaired ECM back in, and no more P2118 code! The problem is when I tried to drive the cruiser away from the shop, it was still in limp mode (little response from accelerator/cap on RPMs at around 2000). This time, however, the CEL is NOT on.

So, the cruiser is stuck in limp mode but without any code. My mechanic has been able to get it out of limp mode by leaving the battery disconnected overnight, and taking it for a spin the next morning, but it will only travel about 1-2 miles before limp mode returning. It seems as if once the engine is warm, something triggers limp mode.

My mechanic has examined all the wiring again and everything looks good. We are not sure what is going on. He took at look at the transmission fluid and it is not a pretty color. Because of the relationship between transmissions and limp mode, we are going to go ahead and drop the pan, clean it out, and then exchange all the ATF with our fingers crossed that a happier transmission will solve the problem. But if that doesn't work, 🤷‍♂️.

Anyone encountered anything like this? Limp mode but no code or CEL?
 
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UPDATE: In advance of a transmission fluid exchange, my mechanic dropped the transmission pan to examine for potential tranny damage and to change the filter. Reinstalled and refilled. Still in limp mode, but now it throws a code: P2102 -- Throttle Actuator Control Motor Circuit Low.

Likely causes include bad throttle body (throttle motor) WHICH IS BRAND NEW and bad ECM--WHICH IS PURPORTEDLY REPAIRED.

So the good news we have a code, instead of stabbing in the dark. The bad news is the code implicates parts which have been replaced or repaired.

Anyone ever dealt with P2102?
 

kruisinkid

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are you sure it doesnt need to be driven more to relearn with the new throttle motor? i swear there was a thread within the last 2 or 3 months where a guy replaced his motor and had a helluva time getting things smooth again but there was a few steps of things he had to do to have the new motor get "settled". sorry very vague. i will try and search for it too. maybe look at youtube for relearning a throttle body motor
 
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I didn't know of the warm up/key to on/key to off/key to start/put in drive relearn. The idle upon plugging the computer back in was pretty wild. I'll dig a little bit for procedure upon reinstalling ECM.
 

kruisinkid

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has the throttle position sensor been confirmed as good?
is the MAF clean and remembered to plug it back in? i nearly always forget to plug it back in before i start everything back up
 
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are you sure it doesnt need to be driven more to relearn with the new throttle motor?

I would have loved to have driven it more with new throttle motor, but we haven't been able to shake limp mode.

I appreciate the help troubleshooting.

On the throttle position sensor, my understanding is that on the 2005, the TPS is built into the throttle body rather than a separate part. This is unlike earlier 100s. We've been eyeing the pedal travel sensor on the accelerator itself suspiciously, but that was before P2102 showed up today.

We haven't checked the MAF for issues. That's a good idea.
 

kruisinkid

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yeah i hear you on the drive to relearn. this fail safe mode sounds sucky.
have you replaced the ETCS fuse regardless of whether it meters out as good. its not crazy to have a fuse pass a continuity test and still be flakey. the ECM circuit could bench test as good but if its not getting proper juice from that ETCS fuse, that could be why the current is so low.

if you go to try that relearn process from the video, i would certainly clear that DTC code after its warmed up.
 

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