2011 Silverado 5.3l Reduced Engine Power Issues

Lars Swenson · October 27, 2022

I am new to the forum page and am hoping to get an idea as to why i am getting the REP on my 2011 5.3l.

Symptoms: When actually driving if put a decent load to the accelerator i can feel that it is responsive to a point, then it loses responsiveness and goes into REP mode, stabilitrack comes etc. The codes that get thrown include P1516, P0223, P0121, P1618. However, when i erase the codes with the OBDII scanner the truck will sit and idle and i can rev like there is no tomorrow including up to 5k+ rpm held. Soon as i take it out for a 5 minute spin the truck acts up and goes into REP. Essentially did the fix for each code that is being displayed repeatedly. Every time i hit REP mode the same codes come up.

Already Tried: I have already replaced the throttle body, TPS, pedal sensor, ignition switch, TPS wiring harness (there was a small cut in one wire), checked voltage on ecm (14v), checked sensor agreement (the pedal and TPS on throttle body) which are in agreement and receiving proper voltage, cleaned and re-secured all grounds on block, frame, and body, double checked the fuses and relay for the throttle system and also checked for any mice chewing of wires. Inspected under the fuse box (yes pulled it out and looked underneath. Checked that the positive cable to the fuse box was clean and secure.

However i cannot get this issue fixed. Any help would be appreciated. Do actually need a new ECU? To me that's just hard to believe.

Edited October 27, 2022 by Lars Swenson