Trunk Key Cylinder Switch Failure
The trunk lock cylinder switch has failed or disconnected, preventing the vehicle from detecting when the trunk key is turned. Think of it like a light switch that no longer tells the car when someone tries to unlock the trunk mechanically.
The ECU monitors voltage signals from the trunk key cylinder switch when the key is inserted and turned. A properly functioning switch sends a signal transition from low to high voltage. The ECU expects to detect this state change within a specific voltage window; if no signal is detected or the signal remains constant, a fault is logged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Signal Voltage | 0-5V transition when key is turned | No voltage change detected or stuck at single voltage level |
| Signal Response Time | <500ms key turn detection | No response or delayed >1s |
Code B2108 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B2108 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.