What Does B1421 Mean?
This code indicates the Body Control Module (BCM) has detected an abnormal electrical condition in the passenger power window motor circuit where current is flowing directly to ground instead of through the intended path. This suggests a short circuit condition that causes excessive current draw and prevents proper window operation. The BCM monitors the motor circuit and sets this code when resistance to ground falls below the expected threshold.
Common Causes
40%
Damaged or chafed wiring harness between door jamb and door panel causing wire insulation to wear through and contact metal body/door frame
30%
Internal short circuit within the passenger window motor itself due to failed commutator, brush assembly, or armature winding insulation breakdown
20%
Water intrusion into door panel causing corrosion and short circuit at motor connector or window switch terminals
10%
Failed window switch with internal short to ground or defective BCM power window relay
Diagnostic Steps
1
Step 1: Perform visual inspection of door jamb harness for visible damage, chafing, or pinched wires. Flex harness while observing for breaks or exposed copper. Check for water stains or moisture in door panel and inspect drain holes for blockage.
2
Step 2: Disconnect the passenger window motor connector. Using a digital multimeter, measure resistance between each motor terminal and ground with switch in neutral position. Reading should be >10k ohms; <100 ohms confirms short to ground in motor.
3
Step 3: With motor disconnected, check resistance to ground on both motor feed wires at the motor connector (harness side). If either wire shows <5 ohms to ground, inspect wiring from BCM to motor, paying special attention to door jamb area. If >10k ohms, motor is faulty.
4
Step 4: If wiring tests good, isolate window switch by disconnecting it and measuring resistance between switch terminals and ground. <100 ohms indicates faulty switch. Check switch connector for corrosion or water damage.
5
Step 5: After repair (motor replacement, wiring repair, or switch replacement), clear codes, operate window through full up/down cycles multiple times, and verify code does not return. Check amp draw during operation (typical 3-8 amps depending on vehicle).
Estimated Repair Cost
$150 - $550
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an abnormal electrical condition in the passenger power window motor circuit where current is flowing directly to ground instead of through the intended path. This suggests a short circuit condition that causes excessive current draw and...
The most common cause of B1421 (Passenger Power Window Motor Circuit Short To Ground) is: Damaged or chafed wiring harness between door jamb and door panel causing wire insulation to wear through and contact metal body/door frame
Typical repair costs for B1421 range from $150 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects passenger window convenience function. No immediate safety risk unless window is stuck in down position during inclement weather, allowing water intrusion into cabin.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1421 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical - Power Window System
Difficulty
Type
Manufacturer
Recommended Tools
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