The B1318 OBD2 fault code relates to the battery power relay circuit. This relay controls power distribution to body electrical systems. When the circuit circuit failure, affected systems may lose power or operate intermittently.

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

Symptoms

• Electrical systems losing power intermittently
• Dashboard warning lights
• Possible no-start condition
• Battery drain issues

Common Causes

• Failed relay — burnt contacts or coil
• a general circuit failure is detected — can result from wiring faults, connector issues, or component failure
• Wiring issues — damaged power or control circuits
• Poor connections — corrosion at relay socket

Step-by-Step Diagnosis

1. Scan with OBD2 tool — Confirm B1318.
2. Test relay — Swap with known-good relay or test with multimeter.
3. Inspect wiring — Check power and control circuits.
4. Check connections — Clean relay socket contacts.

Repair & Solutions

• Replace relay if faulty ($10–$30 part).
• Repair wiring as needed.
• Clean and secure connections.

Related Codes

• B1315 — Battery Saver Relay Coil Circuit Short To Battery
• B1316 — Battery Saver Relay Coil Circuit Short To Ground
• B1317 — Battery Voltage High

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.