Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2003 Chevrolet Express 1/2 Ton Van V6-4.3L VIN XFACTORY OEM SERVICE PROCEDURE
Power Mode Mismatch
POWER MODE MISMATCH
CIRCUIT DESCRIPTION
Normal vehicle class 2 communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by the power mode master (PMM) module in order to determine the correct power mode. The PMM communicates the system power mode to all class 2 modules on the class 2 serial data line. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
6. This step tests for battery voltage on the signal circuits that are not required.
7. This step tests for no battery voltage on the required signal circuits.
8. If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
9. This step eliminates open circuits as the cause of the malfunction.
CIRCUIT DESCRIPTION
Normal vehicle class 2 communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by the power mode master (PMM) module in order to determine the correct power mode. The PMM communicates the system power mode to all class 2 modules on the class 2 serial data line. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.
TEST DESCRIPTION
Step 1:
Steps 2-5:
Steps 6-7:
Steps 8-12:
Steps 13-14:
The numbers below refer to the step numbers on the diagnostic table.
6. This step tests for battery voltage on the signal circuits that are not required.
7. This step tests for no battery voltage on the required signal circuits.
8. If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
9. This step eliminates open circuits as the cause of the malfunction.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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