Passenger's Front Seat Up Switch Circuit Short to Battery
The passenger front seat up switch is stuck in a shorted position, sending a constant 'battery voltage' signal to the seat control module instead of a proper on/off signal. It's like a light switch permanently jammed in the 'on' position, preventing the seat from responding to commands.
The seat control module monitors the voltage signal from the up switch circuit. Normally, the switch toggles between ground (0V) and battery voltage (12V) when pressed. A short to battery means the circuit is stuck at 12V constantly, indicating a mechanical or electrical failure in the switch assembly.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Signal Voltage | 0V (unpressed) to 12V (pressed, momentary) | Constant 12V without switch activation |
| Circuit Continuity | Open circuit when unpressed; closed when pressed | Continuous closed circuit (shorted to battery) |
Code B1977 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, B1977 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.