B1321: Driver Door Ajar Circuit Short to Battery
The B1321 code indicates that the vehicle's body control module has detected a short to battery voltage in the driver door ajar circuit. This circuit monitors the driver door switch to determine if the door is open or closed. A short to battery means the circuit is receiving constant voltage when it shouldn't, causing the module to incorrectly interpret the door as open or detect a circuit fault. This code is specific to Ford Motor Company and its associated brands, used in comfort and convenience systems.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty driver door ajar switch with internal short
- Damaged wiring insulation causing a short to a power wire
- Corroded or bent pins in the door switch connector causing a short
- Internal failure in the body control module (GEM/BCM) affecting the detection circuit
- Aftermarket electrical accessories interfering with the circuit
3. Symptoms You Will Notice
- Door ajar warning light stays on even when the driver door is closed
- Interior dome light stays on or fails to turn off
- Remote keyless entry or alarm system malfunctions
4. Step-by-Step Diagnosis
Scan for other codes and check freeze frame data
Inspect the driver door ajar switch and its connector for damage, corrosion, or bent pins
Test the switch circuit for voltage with the door closed; should be low, not battery voltage
Check wiring harness for chafing or shorts to power wires
If wiring and switch are okay, test the body control module for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the door ajar warning may be distracting and the interior lights may stay on, draining the battery. It is recommended to diagnose and repair the issue soon.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the switch, wiring, or body control module needs replacement. Diagnostic fees are usually around $100.