Hope this helps:
03 Reduced Engine Power - DTCs P0120, P0220, P1516 and/or P1518 - 03 Model Year Full Size Trucks and Utilities with 4.8, 5.3 or 6.0 Engines - kw CEL light low LQ4 LQ9 LR4 MIL reducedpwrmde #PIP3042A - (Aug 30, 2004)
The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Service Engine Soon Light and / or Reduced Engine Power Mode due to any of the following DTCs: P0120, P0220, P1516 and/or P1518.
If the SI diagnosis and bulletin 03-06-04-032 did not isolate a concern, the following information may help:
1. Inspect the Yellow TAC Motor Control Circuit (581) about 1 inch to 4 inches from the throttle body connector to see if it is broken inside of the insulation.
2. Inspect S102 if there is a P1518 stored. S102 is in the engine harness and is 5.5 inches from the MAP Sensor.
3. Install that latest engine diagnostic calibrations in the PCM. Some 2003 model year vehicles have updated engine diagnostic calibrations available to address DTCs P0120, P0220, P1516 and or P1518. The title of the updated engine diagnostic calibration in TIS2000 is "New calibration to eliminate setting of P0120, P0220, or P1516 with the engine not running. Includes diagnostic enhancements for P1518."
If the above did not help, replace the throttle body and retorque it to 45 lb/in on the 1st pass and 89 lb/in on the second and final pass.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
(03 Cadillac Escalade) and (03 Chevrolet Avalanche) and (03 Chevrolet Silverado)and (03 Chevrolet Suburban) and (03 Chevrolet Tahoe) and (03 GMC Sierra) and (03 GMC Yukon) and (03 Hummer H2)
Sunday, September 25th, 2011 AT 5:41 PM