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The SLC Clubhouse RCR SLC Build Logs and Technical Questions

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Old 14th July 2017, 01:40 PM   #1
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Help! Throttle position sensor error

So I'm 100 miles from home at a car show . 7 miles from the show the check engine light comes on and no response to the throttle. Reads code 1238. I let it sit for a while and tried restarting the engine. No check engine light, throttle works fine. I'm a bit concerned about driving all the way tomorrow.
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Old 14th July 2017, 02:12 PM   #2
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Re: Help! Throttle position sensor error

Have you had any heat issues?

"""
The primary reason why this part fails is due to exposure to high heat, as it's typically located on the floorboard next to the firewall of the vehicle, in very close proximity to the engine. """
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Old 14th July 2017, 02:18 PM   #3
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Re: Help! Throttle position sensor error

No heatissues at all
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Old 14th July 2017, 09:09 PM   #4
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Re: Help! Throttle position sensor error

In my experience, TPS are susceptible to carbon tracking which can many times be temporarily cleaned up by simply exercising the TPS through its full range of motion (engine off of course) a dozen times or so.
I'm dating myself, but maybe some of you remember the scratchy volume knob on the radio or stereo system? If you exercised the knob quickly - it would perform adequately for a while.. Same thing - same issue - actually the very same ancient technology..
Will it act up again? Probably. You just exercise it and reboot the ECU and you're on your way. Be aware though, that you could be feeding somewhat dirty signals to the ECU. There is generally fiter circuitry that does a remedial "cleanup" of the signal - so it's not quite as hairy as it would seem...
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Old 15th July 2017, 01:46 AM   #5
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Re: Help! Throttle position sensor error

Is your charging system working good Pete? The ECM watches the voltage of the tps/app circuit carefully and will set a code if the charging system starts to go bad.

Are you sure the code is 1238? I don't see a listing for it. 2138 is a common code for the accelerator pedal position sensor.

Last edited by KENS80V; 15th July 2017 at 02:16 AM.
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Old 15th July 2017, 04:23 PM   #6
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Re: Help! Throttle position sensor error

The code is 2138. Charging system seems fine, showing ~14.5v with the engine running.

Happened again this morning, so I called a friend with a trailer for a rescue. Got it home now, but not really sure what to replace. I guess I'll start with replacing the electronic throttle pedal assembly.
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Old 15th July 2017, 04:42 PM   #7
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Re: Help! Throttle position sensor error

Did you use an extension harness to get the wiring to reach the pedal assembly or did you just unravel the harness and pull out the existing wiring to make it reach. The code has to do with the two sensors in the pedal assembly (voltage reading between the two sensors not matching within parameters). It's either the pedal assembly or the wiring of it back to the ECM.

Last edited by KENS80V; 15th July 2017 at 06:25 PM.
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Old 16th July 2017, 04:38 AM   #8
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Re: Help! Throttle position sensor error

Quote:
Originally Posted by PeteB View Post
The code is 2138. Charging system seems fine, showing ~14.5v with the engine running.

Happened again this morning, so I called a friend with a trailer for a rescue. Got it home now, but not really sure what to replace. I guess I'll start with replacing the electronic throttle pedal assembly.
Likely only 3 things:
throttle pedal or throttle body.

if you used a wiring harness extension or did a DIY wiring harness wiring lengthening that could cause it

also, if your tuner played with the throttle body vs pedal positioning in the ecu your ecu might need to be replaced (playing with that area of the ecu can damage or brick the ecu, and it usually doesn't happen right away)
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Old 16th July 2017, 12:43 PM   #9
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Re: Help! Throttle position sensor error

I didn't extend the harness.

Ordered a new throttle pedal assembly, should be here by Wed. Don't understand why a brand new one only lasted 1200 miles.
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Old 16th July 2017, 01:20 PM   #10
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Re: Help! Throttle position sensor error

Did exercising it through full cycles do any good at all?
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Old 16th July 2017, 02:15 PM   #11
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Re: Help! Throttle position sensor error

Quote:
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Did exercising it through full cycles do any good at all?
I took the intake tube off and pushed the throttle plate back and forth a few times, but there's no way to exercise the throttle plate without the engine running with an electronic throttle.
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Old 16th July 2017, 02:33 PM   #12
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Re: Help! Throttle position sensor error

Quote:
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I didn't extend the harness.

Ordered a new throttle pedal assembly, should be here by Wed. Don't understand why a brand new one only lasted 1200 miles.
it can also be the throttle body - you need to make sure the style of tb (gold vs silver .... late vs early model) is matched to how your ECU is programmed (and you can't change this).

it's also possible there's an issue with the wiring harness - with one of the GMPP wiring harness I bought the pedal would work for 2 or 3 minutes after the ecu was on, then just stop working. Replaced the whole wiring harness and no more issues (and the wiring harness before that one had no pedal issues, so clearly wiring harness issue). I imagine this issue would have showed up much earlier on, but maybe something isn't soldered/connected good enough and worked its way loose.
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Old 16th July 2017, 05:13 PM   #13
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Re: Help! Throttle position sensor error

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Originally Posted by EFNFAST View Post
it can also be the throttle body - you need to make sure the style of tb (gold vs silver .... late vs early model) is matched to how your ECU is programmed (and you can't change this).

it's also possible there's an issue with the wiring harness - with one of the GMPP wiring harness I bought the pedal would work for 2 or 3 minutes after the ecu was on, then just stop working. Replaced the whole wiring harness and no more issues (and the wiring harness before that one had no pedal issues, so clearly wiring harness issue). I imagine this issue would have showed up much earlier on, but maybe something isn't soldered/connected good enough and worked its way loose.
I had forgotten about this....
We actually had it happen to a 2010 Camaro SS / LS3 that we gutted for a racecar back in 2009-10.. Opting to save weight and time we installed the GM Performance Parts wiring harness. Doggoned thing stopped responding to pedal input and set a code. We would reset the codes and it would work again for a few mins.
As it turned out, we had to replace the Throttle Body with the GMPP unit before the system worked together. That was a bitter pill to swallow because at that time, the TB was something like $450!
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Old 17th July 2017, 11:20 PM   #14
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Re: Help! Throttle position sensor error

Quote:
Originally Posted by Big-Foot View Post
I had forgotten about this....
We actually had it happen to a 2010 Camaro SS / LS3 that we gutted for a racecar back in 2009-10.. Opting to save weight and time we installed the GM Performance Parts wiring harness. Doggoned thing stopped responding to pedal input and set a code. We would reset the codes and it would work again for a few mins.
As it turned out, we had to replace the Throttle Body with the GMPP unit before the system worked together. That was a bitter pill to swallow because at that time, the TB was something like $450!
yea, there's 2 style of LS throttle bodies - early and late model - they look almost the same (one is gold throttle plate, one is silver), same electrical connector, but they open in reverse of eachother and the dbw doesn't like if the ecu is mis-matched to the throttle body
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Old 21st July 2017, 09:20 PM   #15
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Re: Help! Throttle position sensor error

Installed a new gas pedal. No codes and seems to be working. Hopefully this solves the problem
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Old 22nd July 2017, 02:05 PM   #16
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Re: Help! Throttle position sensor error

Great to hear there is a resolution, Pete!
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