Airbag Sensor #1 Circuit Short to Ground
Diagnostic trouble code B1901 indicates a short to ground in the power or return circuit of the #1 impact sensor in the airbag system. This circuit connects the Restraints Control Module (RCM) to the first collision detection sensor. A short to ground disrupts proper communication or power to the sensor, which may prevent the airbags from deploying during a crash or cause inadvertent deployment. The RCM continuously monitors circuit resistance and voltage; when it detects abnormally low resistance or near-zero voltage, it sets this code.
1. Commonly Affected Makes
2. Most Common Causes
- Physical damage to the impact sensor wiring harness
- Chafed or pinched wiring making contact with chassis ground
- Corroded or moisture-contaminated impact sensor connector
- Internal short circuit in the #1 impact sensor
- Faulty RCM monitoring circuit
- Incorrect previous repair or modification to the airbag system
3. Symptoms You Will Notice
- Airbag warning light illuminated on the dashboard
- Airbag system may be disabled or inoperative
4. Step-by-Step Diagnosis
Scan the RCM for B1901 and any related codes
Visually inspect the #1 impact sensor wiring and connector for damage, corrosion, or grounding
Disconnect the sensor and measure resistance between signal and ground; compare to specifications
Check for continuity to ground on the sensor circuit with the sensor disconnected
If wiring is intact, test or replace the #1 impact sensor
If sensor replacement does not clear the code, diagnose the RCM for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe. The airbag system may not deploy in a collision, increasing the risk of injury. Have the vehicle repaired immediately.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the issue is wiring repair, sensor replacement, or RCM replacement.