Question: HELP!! Constant failure of throttle position sensors - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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Old 09-25-2014, 06:57 PM   #1 (permalink)
w2rivers
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HELP!! Constant failure of throttle position sensors

2001 Silverado 2500HD Duramax, Allison. 81,000 miles and no mods. I have replaced the throttle position sensor (throttle assembly) 3 times and it has failed again. I am able to pull up a code but never a check engine light. We have checked the pins for looseness. Replaced with GM parts.

After replacing with new part there is a period that it works ok then it fails and may fail continuously and at random times. Last time it failed 5 times over a 50 mile run. Since it is used to pull a 5th wheel it has become a real safety hazard.

I have had it into 4 different repair shops with no change other than my bank account. I would really like some thoughtful advice if not an simular experience and resolution to this problem.

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Old 09-25-2014, 07:49 PM   #2 (permalink)
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What exactly is the code?

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Old 09-25-2014, 10:55 PM   #3 (permalink)
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One failed APPS is rare enough, but 3 is a red flag you have a wiring issue, not a sensor issue. Foolw your APPS harness out to the underhood plug just below the windshield and check the plug out side. Alos check for windshield leaks as it isn't uncommon to get a leak that lets water drip down into the APPS.
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Old 09-26-2014, 11:10 AM   #4 (permalink)
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Quote:
Originally Posted by w2rivers View Post
2001 Silverado 2500HD Duramax, Allison. 81,000 miles and no mods. I have replaced the throttle position sensor (throttle assembly) 3 times and it has failed again. I am able to pull up a code but never a check engine light. We have checked the pins for looseness. Replaced with GM parts.

After replacing with new part there is a period that it works ok then it fails and may fail continuously and at random times. Last time it failed 5 times over a 50 mile run. Since it is used to pull a 5th wheel it has become a real safety hazard.

I have had it into 4 different repair shops with no change other than my bank account. I would really like some thoughtful advice if not an simular experience and resolution to this problem.
I didn't see the exact code to quote it but it refers to the failure of the sensors. There are no interior leaks and failure occurs during very dry weather.

I will check the connections. We think the problem is in another connection away from the throttle assembly but don't know where the wires lead.
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Old 09-26-2014, 02:22 PM   #5 (permalink)
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Quote:
Originally Posted by w2rivers View Post
I didn't see the exact code to quote it but it refers to the failure of the sensors. There are no interior leaks and failure occurs during very dry weather.

I will check the connections. We think the problem is in another connection away from the throttle assembly but don't know where the wires lead.
There should be an a 8 pin plug under the hood mounted to the firewall behind the fuse box for the APPS harness. They used the same APPS I believe for diesel or gas, and I believe the TAC module plugged in there for DBW gassers, for diesels they just put a mating plug there and ran it back to the ECM.
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Old 09-26-2014, 08:41 PM   #6 (permalink)
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I need to test both pin drag and power at that connection. No loose wires that I can see. I tightened the plastic nut as it was loose.
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Old 09-27-2014, 12:38 PM   #7 (permalink)
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So the problem wire should/could be between the throttle and ECM?
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Old 09-27-2014, 02:44 PM   #8 (permalink)
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So the problem wire should/could be between the throttle and ECM?
Yes. Follow your wiring harness from the throttle pedal out to under the hood, and then follow it to see if it plugs into another plug under the hood. I know the 01-02 trucks did, and I'm pretty sure the 03+ trucks did as well. Also make certain your cab grounds and such are good as it doesn't take much of a loss of ground to wreak havoc on electrical parts.
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Old 09-28-2014, 01:04 AM   #9 (permalink)
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After disconnecting the APPS and reconnecting it last night i began driving it today. Oddly it seems to shift shift smoother than before and, although i haven't driven very many miles, so far no issues. Holding my fingers crossed!
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Old 09-28-2014, 11:10 AM   #10 (permalink)
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Moving to electrical forum for a little more exposure.

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