Security system indicator circuit shorted to ground
What it means
B0685. Security system indicator circuit shorted to ground. The body control module cannot light the security indicator and the body warning light comes on.. This Chevy-enhanced code applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.
Findings, check these first
- Faulty light and sunload ambient sensor
- Sensor harness open or shorted
- Poor electrical connection at the sensor
- Faulty body control module
Standard procedure
- Confirm the code with a scan tool
- Inspect the sensor and its connector for damage
- Test the security indicator circuit for a short to ground
- Command the security indicator with the scan tool and watch the lamp
- Replace the sensor or body control module only after circuit tests pass
Look up another code
Press / to jump to the box. Chevy-enhanced powertrain, body, chassis and network codes.
Sources and review
Review: checked against the recorded source material.
- B0685 CHEVROLET Code: Meaning, Causes, and Symptoms | OBD2 Codes - OBD2 Codes
live reference page (obd2-codes.co)
Supports: CHEVROLET and GM-family meaning and likely causes for B0685
Fetched directly. B0685 reads "Security System Indicator Circuit Short to Ground".
- Code B0685 meaning and causes | OBDII.pro
live reference page (obdii.pro)
Supports: independent corroboration of the GM meaning
Fetched directly. obdii.pro is a separate publisher and gives the GM meaning as: Security system indicator circuit malfunction More details about the error B0685 and possible reasons for its occurrence.
Last updated 2026-10-02.
Report a correction for B0685. Include your vehicle, the issue and a source if you have one.
This fault sits in the GM theft deterrent system. The GM security codes and Passlock relearn guide covers the families and the relearn cycles.