The B1240 OBD2 fault code relates to the Wiper Washer Rear Pump Relay circuit. This relay or circuit controls rear wiper and washer operation. When the circuit circuit failure, the wiper system may fail to operate correctly.

At AIscanAuto, we help drivers quickly identify OBD2 trouble codes, understand their root causes, and find the right fix.

Symptoms

• Rear wiper not working
• Washer pump not activating
• Intermittent wiper operation
• Possible warning indicator

Common Causes

• Failed relay — burnt contacts
• a general circuit failure is detected — can result from wiring faults, connector issues, or component failure
• Wiring issues — damaged harness
• Motor failure — worn wiper motor

Step-by-Step Diagnosis

1. Scan with OBD2 tool — Confirm B1240.
2. Test wiper operation — Check all speeds and washer.
3. Test relay — Verify with multimeter or swap test.
4. Inspect wiring — Check for damage.

Repair & Solutions

• Replace relay if faulty.
• Repair wiring.
• Replace motor if needed.

Related Codes

• B1237 — Window Feedback Out of Range
• B1238 — Over Temperature Fault
• B1239 — Air Flow Blend Door Driver Circuit Failure

External References

- OBD2Pros — Complete DTC Reference

About This Guide

This diagnostic article is an original guide created by AIscanAuto for educational and troubleshooting purposes. The technical information about OBD2 DTC codes is based on publicly available automotive diagnostic standards and industry best practices. External links provided in the "External References" section are for additional reading and context only — they do not imply endorsement or ownership of third-party content. All repair procedures should be performed by qualified technicians.