What Does B1518 Mean?
This code indicates the Body Control Module (BCM) has detected a short-to-ground condition in the driver's seat occupancy sensor circuit. The occupancy switch is a pressure or weight-sensitive sensor used to determine if someone is sitting in the driver's seat, primarily for airbag deployment and seatbelt warning systems. The BCM detected abnormally low voltage on the sensor signal wire, indicating the circuit is grounded when it should not be.
Common Causes
45%
Damaged or chafed wiring harness under driver's seat causing short to ground from seat movement
30%
Faulty driver seat occupancy sensor or pressure mat with internal short circuit
15%
Corroded or damaged connector at seat sensor or BCM with moisture intrusion causing ground path
10%
Failed Body Control Module with internal circuit fault on sensor input
Diagnostic Steps
1
Step 1: Perform visual inspection of driver's seat area - slide seat fully forward and backward, inspect wiring harness underneath for chafing, pinching, or damage against seat rails and brackets. Look for crushed or exposed wires.
2
Step 2: Disconnect driver seat occupancy sensor connector and inspect both male and female terminals for corrosion, bent pins, moisture, or damage. Check connector retention and seal integrity.
3
Step 3: With sensor disconnected, use digital multimeter to measure resistance between sensor signal wire pin (at harness side) and known good ground. Reading should be infinite (OL). If continuity exists, trace and repair short to ground in harness between sensor and BCM.
4
Step 4: Measure resistance across seat occupancy sensor terminals with sensor disconnected. Compare readings to manufacturer specifications (typically 200-2000 ohms depending on design). If sensor shows 0 ohms or very low resistance, replace sensor.
5
Step 5: Reconnect sensor, clear codes, and test by applying weight to driver seat while monitoring live data for sensor status. Verify BCM recognizes occupied/unoccupied states correctly. Check that airbag warning light functions properly and seatbelt chime operates as designed.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short-to-ground condition in the driver's seat occupancy sensor circuit. The occupancy switch is a pressure or weight-sensitive sensor used to determine if someone is sitting in the driver's seat, primarily for airbag deployment and se...
The most common cause of B1518 (Seat Driver Occupied Switch Circuit Short To Ground) is: Damaged or chafed wiring harness under driver's seat causing short to ground from seat movement
Typical repair costs for B1518 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive, but airbag system may not deploy properly or may deploy inappropriately based on incorrect occupancy detection. Seatbelt warning system may malfunction. Repair should be completed promptly to ensure proper airbag function in the event of a collision.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1518 to identify the root cause.
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Quick Info
Category
Body
System
Supplemental Restraint System (SRS) / Airbag System
Difficulty
Type
Manufacturer
Recommended Tools
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