B2100: Driver Door Lock Cylinder Switch Circuit
The B2100 code indicates that the Body Control Module (BCM) or Generic Electronic Module (GEM) has detected a fault in the driver door lock cylinder switch circuit. This switch tells the module when the mechanical key is turned to lock or unlock the door. The fault involves an out-of-range signal, open circuit, or short circuit in the wiring or the switch itself.
1. Commonly Affected Makes
2. Most Common Causes
3. Symptoms You Will Notice
- Driver door power lock may not work
- Keyless entry or remote lock/unlock may fail
- Door ajar warning may stay on
- Interior lights may not operate correctly
4. Step-by-Step Diagnosis
Scan for B2100 and any related codes
Visually inspect the door hinge harness for broken or frayed wires
Test the lock cylinder switch with a multimeter for proper resistance/voltage
Check for continuity and shorts in the signal circuit between switch and BCM/GEM
If wiring and switch are good, suspect BCM/GEM failure
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but you may experience issues with power door locks and keyless entry. The mechanical key should still work to lock/unlock the door.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the switch, wiring, or BCM needs replacement. Diagnostic fees are usually around $100.