B1979

Step 1: Perform visual inspection of passenger seat switch assembly and wiring harness for obvious damage, pinched wires, melted insulation, or signs of liquid intrusion. Check for any aftermarket installations or modifications near the seat area.

Step 2: Disconnect the passenger seat switch connector and use a digital multimeter to measure voltage on the rearward switch circuit terminal at the harness side (vehicle side). With ignition on, you should read 0 volts; if battery voltage (12-14V) is present, the short is in the wiring harness between the connector and BCM.

Step 3: If no voltage was found at the harness connector in Step 2, inspect the switch assembly itself by measuring resistance across the rearward switch terminals with the switch in released and activated positions. Released should show open circuit (infinite resistance), activated should show continuity (near 0 ohms). Any reading showing continuity to the power supply terminal indicates internal switch failure.

Step 4: Inspect all connectors in the circuit path for corrosion, pushed-out pins, or cross-contamination. Pay special attention to connectors under the seat that may be exposed to moisture or debris. Clean and secure all connections.

Step 5: If wiring and switch test normal, perform a BCM input test using bidirectional controls to command the seat motor while monitoring circuit behavior. Check for proper voltage drop and current flow patterns to isolate BCM internal faults.

Step 6: After repair, clear the code, cycle the seat through all adjustment positions multiple times, and verify the code does not return. Test all seat functions to ensure proper operation of memory settings and other seat controls.