B1977

Step 1: Perform visual inspection of passenger seat switch assembly and all visible wiring. Look for signs of water damage, physical damage, crushed wires under seat rails, or burnt/melted connectors. Check for any aftermarket modifications.

Step 2: Disconnect the passenger seat switch connector and use a digital multimeter to measure voltage at the BCM-side connector terminal for the seat up switch circuit. With ignition on, verify if battery voltage (12V+) is present when it should read 0V or reference voltage (typically 5V or less).

Step 3: If battery voltage is present at BCM connector with switch disconnected, inspect the wiring harness routing under the seat and along the B-pillar for pinch points, chafing against metal brackets, or damage from seat track movement. Check continuity between the affected wire and known battery voltage sources.

Step 4: If no wiring damage is found and voltage is normal at BCM side with switch disconnected, test the seat switch assembly by measuring resistance across the up switch terminals. Compare readings to manufacturer specifications (typically open circuit when not pressed, low resistance when activated). Replace switch if internal short is detected.

Step 5: Clear the code and operate the seat up function while monitoring live data with the scan tool. Verify proper voltage readings during switch activation. If code returns immediately without switch activation, suspect BCM internal fault.

Step 6: After repair, cycle the seat through full range of motion, clear codes again, and perform a BCM relearn procedure if available. Verify code does not return and all seat functions operate correctly.