EIC Switch-2 Assembly Circuit Short To Battery
The passenger seat occupancy sensor circuit is receiving too much voltage, like a wire touching the battery instead of properly communicating with the control module. This prevents the system from correctly detecting if someone is sitting in that seat.
The ECM monitors the EIC (Electronic Identification Control) Switch-2 circuit voltage to detect passenger seat occupancy. A shorted-to-battery condition causes the circuit voltage to remain at battery potential instead of switching between ground and signal levels. The ECM expects dynamic voltage changes within a specific range; sustained high voltage triggers the fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Circuit Voltage | 0V to 5V switching pattern | Sustained 12V+ (battery voltage) |
| Signal Pattern | Dynamic transitions on seat state change | Static high voltage regardless of occupancy |
Code B1211 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, B1211 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.