B1540

Step 1: Perform visual inspection of the driver's door wiring harness, especially at the hinge area where flexing occurs. Look for damaged insulation, broken wires, or pinched harness. Inspect all connectors at the mirror switch and BCM for corrosion, pushed-back pins, or moisture intrusion.

Step 2: Using a digital multimeter, check for continuity between the mirror switch connector pins and the BCM connector pins according to wiring diagram specifications. Test each circuit individually with the connector disconnected. An infinite resistance reading confirms an open circuit.

Step 3: If wiring tests good, disconnect the mirror switch assembly and test for internal continuity across switch contacts while activating the switch in different positions. Compare resistance readings to manufacturer specifications (typically less than 5 ohms when closed).

Step 4: If switch tests good, check for proper ground circuit integrity at the switch assembly using a multimeter between the ground pin and known good chassis ground. Resistance should be less than 1 ohm.

Step 5: After identifying and repairing the open circuit (replacing damaged wiring, connector, or switch), clear the DTC code and cycle the mirror switch through all positions to verify proper operation and confirm the code does not return.