03 5.3 LM4 GMT370 Reduced Engine Power due to DTCs P0120, P0220 , P1516 , and/or P1518 - kw GMT305 GMT360 CEL light low MIL no power reduced reducedpwrmde SES

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) 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. This condition is normally very intermittent.

If the published diagnostics did not isolate a concern, the following information may help:

1. Inspect G108 on the left side of the engine block.
2. Install that latest PCM engine diagnostic calibrations. 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 P1516 is the only DTC and the above did not help, replace the throttle body and retorque it using a two step process. It should be torqued to 45 lb/in on the 1st pass and 89 lb/in on the second and final pass. If P1518 is the only DTC and the above did not help, replace the ignition switch.

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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.

(2003 5.3 LM4 GMT360 GMT370 Chevrolet Trail Blazer EXT) and (2003 5.3 LM4 GMT370 GMC Envoy XL) and (2003 5.3 LM4 GMT305 GMC Envoy XUV)

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