2003 Chevrolet GMC S/T Classic Crew Cab Pickups and Utilities 4.3L Engine ONLY - SES Light and EVAP DTC P0442 But No Leak Found - kw driveability harness mil no

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

SES lamp on with DTC P0442 stored in PCM memory. P0442 diagnostics in Service Information may not detect a leak in the EVAP system.

The rear chassis wiring harness may be incorrect on some 2003 S/T Classic Crew Cab Pick-Ups and Utilities built prior to VIN 1GNDT13X83K125206, Built at Linden NJ Plant Code K (11th digit of VIN).

For a Engine Off Natural Vacuum ECM EVAP leak detection the EVAP vent valve needs battery voltage when the key is in the off position, because the system is tested when the ignition is Off.

Perform the following test to ensure that the wiring harness is functioning properly:

1. Cycle ignition key on, then off.
2. With ignition key in the OFF position, raise the vehicle and remove the vent solenoid connector. (Note: In prior years, the engine had to be running to perform this test. Do NOT have a vehicle running to perform this test on 2003 models.)
3. Measure voltage at the vent solenoid connector - there should be 12 volts present.

If voltage is only present with the key in the on position, replace the rear chassis wiring harness.

If the connector measures 12 volts with the key off, or if the new harness has been installed per this PI, use normal diagnostic procedures to root cause the concern. Some preliminary repairs have indicated a possible small leak occurring at the sender to tank seal. This leak may not be detected by the EVAP test cart. To correct this type of leak replace the sender seal and fuel tank sender.

Rear Chassis Wire Harness Part numbers are as follows:

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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. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

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(2003 Chevrolet Blazer 2dr/4dr) and (2003 GMC Jimmy 2dr/4dr) and (2003 Chevrolet S-10 Pickup Crew Cab) and (2003 GMC Sonoma Pickup Crew Cab)