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FIXITMAN
FIXITMAN, Master Technician
Category: GM
Satisfied Customers: 17143
Experience:  ASE Master Certified
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My check engine is on, it was a p0121 I believe, I replaced

Customer Question

My check engine is on, it was a p0121 I believe, I replaced the throttle positioning pedal I believe that's what it's called the whole pedal(unit) not just the sensor. Anyway, I doubled-triple checked everything was put back the same way it was as well as the plug and gray clip. So turned it on light was still on(check engine) so I turned it off put it in just the "on" position plugged the scanner and cleared it, I tried my auto start 3 times because it hadn't been working ever since the light came on and it worked! So I thought it was good, so next morning before I walked it the door I tried it and started right away, I get in my truck put the key and turn it and what do I see?? That freaking light back on! So I put the scanner again I get the same code(p0121) cleared it went away go to work it stayed off and comes back on when I turned it on after work it's been 8 days and gotten the same code but I haven't noticed any crazy rpms going wack before or after replacing the tps but I'm honestly out of options on what it could be. My next move is taking the throttle body off and clean it and see what that does. Any ideas what else I could try or what i might have done wrong? Any info/constructive criticism is welcome. Thanks in advance.
Submitted: 11 months ago.
Category: GM
Expert:  FIXITMAN replied 11 months ago.

Hello, my name is Bobby. Thank you for the question. Most of the time when this code comes up there are some other common issues. Most of the time the issue is actually the connection at the throttle body or the throttle body itself. I have also seen issues with the wiring to the accelerator pedal where it goes behind the driver kick panel. There are issues with water getting in there and causing this. I would start by checking this wiring and then adding dielectric grease to the connection on the throttle body to see if it helps. Then replace the throttle body if needed. Please let me know if you need more help.

Customer: replied 11 months ago.
One thing I noticed when replacing the accelerator pedal that there's some sort of a "pin" not part of the replacement part but when I took off the old one I kinda wiggled it and it had a lil play so I put the new one and checked that pin again and it had the same "play" to it would that have anything to do or affect the "positioning" sensor? And thanks for that tip I wil check the wiring and for rust in the connectors.
Expert:  FIXITMAN replied 11 months ago.

Yes, that can cause this. If there is a loose connection then replace the connector on the pedal assembly. Most auto parts stores sell these.