B1518: Driver Seat Occupancy Switch Short to Ground
The B1518 code indicates a short-to-ground fault in the driver seat occupancy switch circuit. This switch is part of the Supplemental Restraint System (SRS) and detects whether the driver seat is occupied, enabling or disabling the airbag warning light and adjusting deployment logic during a collision. When the Restraints Control Module (RCM) detects abnormally low resistance (near 0 ohms) in this circuit, it interprets this as a short to ground and sets the fault code.
1. Commonly Affected Makes
2. Most Common Causes
- Damaged or internally shorted driver seat occupancy switch
- Wiring insulation damage causing contact with body or chassis
- Corroded, bent, or shorted pins in the switch connector
- Internal failure of the Restraints Control Module (RCM) (uncommon)
- Seat belt pretensioner assembly or floor mat pinching the wiring
3. Symptoms You Will Notice
- Airbag warning light illuminated on the dashboard
- SRS system may be disabled or operate incorrectly
4. Step-by-Step Diagnosis
Scan the vehicle for all SRS codes and note freeze frame data
Visually inspect the driver seat occupancy switch wiring and connector for damage, corrosion, or pinched wires
Measure resistance at the switch connector; compare to manufacturer specifications
If wiring and switch check out, test the RCM for proper operation or perform a known-good component swap
5. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. The SRS system may not deploy airbags correctly in a crash, increasing injury risk. Have the vehicle repaired immediately.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on whether the switch, wiring, or RCM needs replacement and labor rates.