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reduced power mode

reduced power mode

Postby Beehler [OP] » Nov 10 2019, 5:23am


2002 GMC 2500HD, 8.1 liter, Allison Transmission.

The truck has been sitting for about 3 weeks. The day before my wife reset the clock on an after market radio that was installed a couple years ago.

The truck started fine, but immediately went in to reduced power mode and the service engine soon light came on. Shutting off the truck and re-staring it produce the same result 2 more times. On the fourth start the truck reverted to normal mode, but the service engine soon light stayed on.

Since then I have driven the truck about 50 miles with multiple starts and everything has been fine. The other day I reset the "service engine soon" light. Hooking up the scanner revealed two codes "P1515" and "P1515 pending." I cleared these codes and have not driven the truck since.

Any suggestions? Thanks in advance!
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Re: reduced power mode

Postby Rambodog » Nov 11 2019, 5:25pm

There is a Yellow wire coming off the throttle body connector that can break inside the insulation. Grab the wire about 5 or 6" above the connector and try moving it around and give it a tug to see if it is connected solid. I saw a thread on a different site that stated. "When I have a vehicle with these codes and reduced power, I update the PCM (check Dealer for update). Replace the throttle body and the harness connector and check the ground on pass side head".
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