B1421: Passenger Window Motor Circuit Short to Ground
Diagnostic trouble code B1421 indicates a short to ground in the passenger power window motor circuit. This code is specific to Toyota, Lexus, and Scion vehicles, where the body ECU monitors the circuit resistance or current. A short to ground prevents the window motor from operating correctly, often causing the window to not respond to the switch.
1. Commonly Affected Makes
2. Most Common Causes
- Passenger window motor wiring shorted to chassis or ground
- Passenger window motor with internal winding shorted to housing
- Moisture or corrosion in the motor or switch connector causing a ground leak
- Faulty body ECU with internal short in the control circuit
- Master window switch with internal insulation failure
3. Symptoms You Will Notice
- Passenger window does not move when using the switch
- Window may move slowly or intermittently
- Other windows may still operate normally
4. Step-by-Step Diagnosis
Check for blown fuses related to the power window circuit
Inspect the passenger window motor connector for corrosion or damage
Test the motor circuit for continuity to ground using a multimeter
Verify the body ECU is receiving proper signals from the switch
If wiring and motor check out, test the body ECU for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the passenger window will not operate. The issue does not affect vehicle drivability.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on whether the wiring, motor, or body ECU needs replacement.