B1814

Step 1: Locate the rear wiper relay assembly (typically in underhood fuse box or rear compartment) and perform visual inspection for corrosion, water intrusion, damaged connectors, or burnt relay. Check associated fuse with test light or multimeter for continuity.

Step 2: With ignition on, use a multimeter to measure voltage at relay coil power supply terminal (should read battery voltage). Then check for continuity between relay coil ground terminal and chassis ground (should read less than 1 ohm resistance).

Step 3: Disconnect relay and measure coil resistance across relay terminals with multimeter (typical specification 70-120 ohms). If out of spec or open circuit, replace relay. If within spec, reconnect and monitor voltage drop across coil during wiper operation.

Step 4: Backprobe BCM connector at relay control circuit pin with multimeter while commanding rear wiper function. BCM should provide ground path or switched power (manufacturer-specific). If no signal present, inspect wiring harness for breaks or shorts between BCM and relay.

Step 5: If wiring and relay test good, measure resistance in complete circuit from BCM to relay including all connectors. Values exceeding 5 ohms indicate high resistance requiring connector cleaning or harness repair.

Step 6: After repairs, clear codes and cycle rear wiper through all functions multiple times. Verify wiper parks correctly in down position and code does not return. Road test in wet conditions if possible to confirm proper operation under load.