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Dave Nova
Dave Nova, Chevrolet Technician
Category: Chevy
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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hello Im working on an 05 chevy cobalt, and i got a code that

Resolved Question:

hello I'm working on an 05 chevy cobalt, and i got a code that is PO121 and I change the throttle positioning sensor but the RPM is still surging up and down and is running a little rough. And the engine has a vin code F
Submitted: 7 years ago.
Category: Chevy
Expert:  Dave Nova replied 7 years ago.

This could be due to a shorted wire in the trunk. I have included the technical service bulletin that covers this problem.


#PIC4252: Buck While Driving Stall SES Light Flash Door Locks Cycle CD Player Skip Clock Reset - keywords amp blown fuse ground idle inop inoperative intermittent L61 LE5 P0121 short STG surge trunk wire - (Oct 5, 2006)

Subject:Buck While Driving, Stall, SES Light Flash, Door Locks Cycle, CD Player Skip, Clock Reset

Models:2005-2007 Chevrolet Cobalt
2005-2006 Pontiac Pursuit
2007 Pontiac G5


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


Owner complaining that the vehicle would buck while driving at times, may stall, ses light would flash, door locks cycle, cd player skip and reload, and clock reset to 12:00 It has been found that the Red/Black wire circuit #142 shorting on left rear inner quarter panel. It was not blowing the 50 amp maxi fuse right next to the battery in the trunk. This circuit feeds, hot all the time long term memory for ecm, tcm, bcm, radio, rcdlr. The wire is taped along with one other wire, the location is just to the rear of the subwoofer (must remove to access to remove trunk liner).

Note:: Your vehicle may or may NOT have a subwoofer, however the wiring is the same.


Remove damaged section of wire and repair, install insulation over edge of inner quarter panel, and install conduit..






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