B2315

Step 1: Visually inspect the passenger door wiring harness from door jamb to mirror for chafing, pinching, or visible damage. Flex the harness while monitoring for intermittent faults. Check the door jamb boot area where wires commonly break.

Step 2: Disconnect the passenger mirror electrical connector and inspect for corrosion, water intrusion, or damaged pins. Using a digital multimeter, measure resistance from the horizontal feedback potentiometer signal wire (typically 3-5 wires in connector) to ground with mirror disconnected. Reading should be infinite ohms; any continuity indicates a short.

Step 3: With mirror still disconnected, measure resistance across the feedback potentiometer terminals while manually moving the mirror horizontally. Should see smooth resistance change between approximately 500-5000 ohms (varies by manufacturer). Erratic readings or direct continuity to ground indicates failed potentiometer.

Step 4: If wiring and potentiometer test good, backprobe the BCM connector at the mirror feedback circuit pin with mirror connected. Measure voltage while commanding mirror movement (typically 5V reference). If voltage drops to zero or shows short characteristics with good mirror assembly, suspect BCM fault.

Step 5: Perform continuity test on mirror harness from BCM connector to mirror connector with both disconnected. Should show less than 5 ohms resistance on all circuits with no shorts to ground or other circuits.

Step 6: After repairs, clear codes, cycle mirror through full range of motion in all directions, and verify smooth operation with no binding. Road test and verify code does not return.