Code
B1145
HUMMER
B — Body
Occupant Classification System (OCS) Passenger Detection Circuit Failure
AI status
Completed
Completed
100%
Causes
- Faulty occupant classification sensor (seat mat/pressure sensor)
- Open, short, or corroded wiring / connector in passenger seat harness
- Poor or missing ground or supply to the OCS sensor/module
- Connector contamination or water intrusion in the seat or module
- Damaged or incorrectly installed aftermarket seat cover or seat foam
- Faulty Passenger Airbag/Restraint Control Module (ACM/Sensor Module)
Symptoms
- SRS / airbag warning lamp illuminated on dash
- Passenger airbag status message incorrect (always off or on)
- Passenger airbag disabled when seat is occupied or enabled when empty
- Occupant classification warning or SERVICE AIRBAG message
- Possible diagnostic trouble codes stored in the restraint control module
What to check
- Read and record all airbag/OCS-related DTCs and freeze frame data with a capable scan tool
- Visual inspection of passenger seat (covers, foam, mat) and connectors for damage, contamination, or moisture
- Check for aftermarket seat covers or modifications that could interfere with the sensor
- Inspect and wiggle-test the seat wiring harness while watching live data for errors or status changes
- Verify power and ground at the OCS sensor/module connector
- Check for related communication errors (CAN/LIN) to the airbag or body control modules
Signal parameters
- OCS mat resistance or sensor voltage: typically changes between 'no occupant' and 'occupied' — verify against vehicle service manual
- Supply voltage to sensor/module: ~9–16 V (vehicle battery/system voltage) — should be stable
- Ground continuity: low ohms to chassis ground
- Diagnostic self-test result flags from the restraint control module (PASS/FAIL)
- Serial data/diagnostic messages on CAN/LIN indicating OCS status or fault codes
Diagnostic algorithm
- Safety first: disable the battery / SRS power per manufacturer procedure and wait the specified time before working on or near restraint components.
- Use a factory-level scan tool to read all stored codes and freeze-frame data from the airbag/restraint module. Note related codes and timestamps.
- Perform a visual inspection of the passenger seat: remove trim as needed to access the occupant sensor mat, connectors, and wiring. Look for corrosion, moisture, rodent damage, or foreign objects.
- Inspect connectors and harness routing for pin damage, corrosion, looseness, or signs of water entry. Repair/replace any damaged connectors or wiring.
- With the connector disconnected and power removed, measure continuity to ground and check insulation resistance of the sensor harness. Reconnect and backprobing with a scan tool or multimeter, observe supply voltage and signal while simulating occupant weight (follow service manual safe test methods).
- If available, view live OCS sensor parameters on the scan tool. Compare empty vs occupied readings to factory specifications. If readings do not change or are out of spec, suspect the sensor mat or module.
- Check for aftermarket seat covers or dense foam that could mask or change sensor readings; remove/replace as necessary and retest.
- If wiring and connectors are good but sensor readings remain faulty, replace the occupant sensor mat or OCS module as directed by service information. Always use manufacturer-approved replacement parts.
- After repairs, clear codes, reconnect battery, and perform OCS calibration or relearn procedure if required by the manufacturer. Confirm proper operation and that the SRS lamp does not re-illuminate.
- If fault persists after replacing suspect parts, consult wiring diagrams and perform module bench tests or replace the airbag/restraint control module only after confirming upstream/downstream circuits.
Likely causes
- Seat occupant sensor mat or mat harness fault
- Loose, corroded, or pinched connector at the seat or module
- Water/moisture damage in seat cushion or connector
- Aftermarket seat cover or repair that changed sensor operation
- Failure of the OCS/module electronics
Fault status
Status
Passenger detection circuit failure detected by the Occupant Classification System. The system cannot reliably determine passenger presence/weight, which may disable or miscontrol the passenger airbag.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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