Wiper Washer Rear Pump Relay Circuit Failure
The rear wiper washer pump relay isn't responding properly—it's like a switch that won't flip to turn on the pump. The ECU detected an electrical circuit failure in the relay that controls the rear washer system.
The ECU monitors the control circuit voltage and current draw when commanding the rear washer pump relay. It checks for proper relay activation by measuring the voltage drop across the relay coil and verifying pump motor current response. If voltage or current remains outside expected parameters, a circuit failure is detected.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Relay coil voltage | 11-14V when commanded | Below 10V or no voltage detected |
| Pump motor current draw | 2-5 amps during operation | No current or excessive current (short circuit) |
Code B1240 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, B1240 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.