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Code PO121 TPS

Tiny
CHARLES 123
  • MEMBER
  • 2008 CHEVROLET 1500
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Have replaced TPS but check engine light keeps coming back on.
Sunday, August 13th, 2017 AT 10:50 AM

4 Replies

Tiny
DIESEL&AUTOTECH
  • MEMBER
  • 5 POSTS
May not be TPS. Check wiring leading up to TPS.
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Sunday, August 13th, 2017 AT 11:26 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,018 POSTS
First thing is to clean the throttle body. Carbon can cause the throttle to hang and the ECM thinks this is a TPS issue because it cannot close fully.

Next is to look at the data coming from the throttle control system, for that you need a scan tool with bi-directional control. With that on there you can wiggle the harness and see if it is a bad wire/loose connection or similar. You can also watch the system to look at the voltages it is seeing from the TPS.
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Sunday, August 13th, 2017 AT 11:47 AM
Tiny
DIESEL&AUTOTECH
  • MEMBER
  • 5 POSTS
I remember there were a lot of issues on those vehicles with wiring they were trying to push for recall. But Steve is right, clean the throttle body first and see. They may have given you a faulty sensor too. Good luck
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Monday, August 14th, 2017 AT 2:56 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,018 POSTS
Still are pushing for GM to do the replacement TBs and software updates but it is like pushing water with a rake.
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Monday, August 14th, 2017 AT 8:40 AM

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