The B1921 OBD2 fault code relates to the Air Bag Diagnostic Monitor Ground circuit. When the circuit open circuit, the module cannot properly monitor or control this body system.
At AIscanAuto, we help drivers quickly identify OBD2 trouble codes, understand their root causes, and find the right fix.
Symptoms
- Airbag / SRS warning light illuminated
- Seatbelt tensioner may not function
- Possible warning chime
- Safety system deactivated
Common Causes
- Faulty component — internal damage or wear affecting Air Bag Diagnostic Monitor Ground
- Wiring issues — broken, corroded, or chafed wires in the circuit
- Connector problems — loose, oxidized, or moisture-damaged pins
- an open circuit is detected — indicates a break in the circuit path, resulting in no signal transmission
- Module input failure — rare, but the control module input stage may be defective
Step-by-Step Diagnosis
- Scan with OBD2 tool — Confirm B1921 is active. Check for additional DTCs.
- Visual inspection — Examine the Air Bag Diagnostic Monitor Ground wiring and connector for corrosion or damage.
- Check voltage and ground — Use a multimeter to verify proper reference voltage.
- Test component — Compare readings to factory specs. A stuck or erratic signal confirms failure.
- Check for shorts/opens — Perform continuity tests on the wiring between the component and control module.
Repair & Solutions
- If the component is defective, replace the Air Bag Diagnostic Monitor Ground with an OEM or quality aftermarket part.
- Repair any damaged wiring or connectors using proper methods.
- Clear the DTC with an OBD2 scanner and test drive to verify the code does not return.
- If the code persists after component replacement, inspect the control module connector.
Related Codes
- B1918 — Air Bag Memory Clear Circuit Open
- B1919 — Air Bag Memory Clear Circuit Short To Battery
- B1920 — Air Bag Passenger Circuit Failure