Passenger Rear Seat Down Switch Circuit Short to Battery
The passenger rear seat down switch is stuck sending a 'battery voltage' signal to the ECU instead of its normal operating signal, like a light switch that's permanently flipped on. This prevents the system from properly detecting whether the seat is up or down.
The ECU monitors the voltage signal from the rear seat down switch, expecting it to toggle between ground and a mid-range signal when the seat position changes. A short-to-battery condition means the signal is stuck at battery voltage (12V) instead of fluctuating normally, indicating a wiring fault or stuck switch contact.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Signal Voltage | 0V to 5V (switching between states) | Continuous 12V (stuck at battery) |
| Signal Transition Time | Rapid voltage change on seat movement | No voltage change detected |
Code B1973 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, B1973 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.