Air Bag Crash Sensor #1 Feed/Return Circuit Failure
The airbag system's crash sensor #1 has a broken electrical connection, like a phone charger with a frayed wire that won't conduct power properly. The vehicle can't communicate with this sensor to detect collisions, so the airbags won't deploy if needed.
The ECU monitors the voltage and continuity of the crash sensor #1 feed and return circuits. It applies a reference voltage and expects a specific signal response within normal parameters. If the circuit is open, shorted, or has excessive resistance, the ECU detects a fault condition.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Circuit Voltage | 4.5V to 5.5V | Below 1V or above 6V |
| Circuit Resistance | 50 to 500 ohms | Open circuit (∞ ohms) or shorted (<10 ohms) |
Code B1931 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, B1931 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.