What Does B1621 Mean?
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the rear wiper low limit position sensor circuit. Specifically, the circuit is seeing battery voltage when it should not, suggesting a short to power somewhere in the wiring or sensor assembly. The low limit sensor typically detects when the wiper has reached its parked or rest position.
Common Causes
45%
Damaged or chafed wiring harness causing short to battery voltage in the rear wiper motor position sensor circuit
30%
Faulty rear wiper motor assembly with internal short in position sensor circuit
15%
Corroded or moisture-damaged connector at rear wiper motor causing cross-circuit short
10%
Failed Body Control Module (BCM) with internal fault in wiper control circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of rear wiper motor and all associated wiring harness routing from BCM to motor, looking for chafed insulation, pinched wires, or damage near hatch hinge areas and liftgate mechanisms
2
Step 2: Disconnect rear wiper motor connector and inspect for corrosion, moisture intrusion, pushed-back pins, or burnt terminals; clean and apply dielectric grease if contamination found
3
Step 3: With motor disconnected, use digital multimeter to check resistance between the low limit position sensor wire (consult wiring diagram for specific pin) and battery positive; reading should be infinite (open circuit), any continuity indicates short to power in harness
4
Step 4: If harness tests good, check rear wiper motor internal resistance on position sensor terminals per manufacturer specifications (typically 100-500 ohms); out-of-spec readings indicate faulty motor assembly
5
Step 5: Reconnect all components and clear code; operate rear wiper through full cycle and monitor live data for position sensor voltage (should vary between 0-5V depending on position); constant battery voltage confirms component failure
6
Step 6: If all circuits and components test normal, suspect BCM internal fault; verify BCM software is up to date and consider BCM replacement only after all other causes eliminated
Estimated Repair Cost
$120 - $650
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an abnormal voltage condition in the rear wiper low limit position sensor circuit. Specifically, the circuit is seeing battery voltage when it should not, suggesting a short to power somewhere in the wiring or sensor assembly. The l...
The most common cause of B1621 (Wiper Rear Low Limit Input Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to battery voltage in the rear wiper motor position sensor circuit
Typical repair costs for B1621 range from $120 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects rear wiper functionality and does not impact vehicle safety systems. Repair at convenience, though reduced rear visibility during inclement weather should be considered.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1621 to identify the root cause.
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Quick Info
Category
Body
System
Body Control System - Rear Wiper Assembly
Difficulty
Type
Manufacturer
Recommended Tools
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