Code
B1146
HUMMER
B — Body
Occupant Classification System (Passenger) Sensor Circuit Fault
AI status
Completed
Completed
100%
Causes
- Open or short in the passenger occupant sensor signal, reference or ground circuit
- Corroded, loose or damaged connector under the passenger seat
- Failed occupant classification sensor module (pressure/weight sensor or mat)
- Water ingress or contamination of the seat sensor/module
- Poor or missing ground at the seat or chassis
- Intermittent wiring damage from seat movement (harness wear or pinched wire)
Symptoms
- SRS/Airbag warning lamp illuminated
- Passenger airbag disabled or 'passenger airbag off' message when seat occupied
- Passenger presence/weight display incorrect or inconsistent
- DTC B1146 stored or active in the restraint system
- Possible inability to perform OCS calibration until fault is cleared
- Intermittent or permanent loss of passenger seat occupancy detection
What to check
- Use a diagnostic scan tool to read all stored SRS/airbag codes and freeze frame data
- Visually inspect passenger seat area for water damage, contamination or visible damage
- Inspect connector(s) under passenger seat for corrosion, bent pins or loose terminals
- Verify battery voltage is stable (12 V) and perform checks with proper power applied
- Check for related codes (other B1xxx or U0xxx series) that indicate wiring or module communication problems
- Follow manufacturer SRS safety procedures (disable battery per service manual) before disconnecting connectors or removing seat
Signal parameters
- Reference voltage to sensor: typically a regulated 5 V reference from the RCM or occupant classification module
- Signal voltage from sensor: typically a variable 0–5 V analog or low-voltage digital count that changes with occupant load
- Sensor ground continuity and resistance to chassis ground
- Sensor element resistance or impedance (seat mat sensors may show measurable resistance change with applied load)
- CAN or serial data messages shown by scan tool from occupant classification module (presence of expected CAN IDs)
- Voltage drop on signal/ground while performing a wiggle test (check for intermittent connections)
Diagnostic algorithm
- Read and record all SRS/airbag codes and freeze frame with an appropriate scan tool. Note if B1146 is active or stored and any related codes.
- Check vehicle service history: has the seat been removed, repaired, or was the vehicle in a collision? Check for recent work that might have disturbed the harness.
- Visually inspect the passenger seat, under-seat area and seat tracks. Look for water, stains, damaged mat, or debris that could damage the sensor.
- With SRS power disabled per manufacturer procedures (follow service manual; common practice is to disconnect battery and wait the specified time), disconnect the passenger seat connector(s) and inspect pins for corrosion, bent pins, or pushed-out terminals.
- Reconnect battery/power following safety procedures. Backprobe the occupant sensor connector: verify reference voltage (≈5 V) and ground continuity to chassis ground with a digital multimeter. Record values.
- With seat empty and then with a known test weight (manufacturer specified or ~20–30 kg for verification), monitor the sensor signal voltage or live data using the scan tool. The signal should change consistently with load; if not, suspect the sensor or wiring.
- Perform continuity checks between the sensor connector and the RCM/occupant classification module for signal, reference and ground. Repair any open/shorts or chafed wiring found.
- Wiggle test the wiring and seat connectors while monitoring live data to find intermittent faults caused by seat movement.
- If wiring and connectors are good but signal is out of spec or no change with load, replace the passenger occupant sensor/module per service procedure.
- After repair or replacement, perform required occupant classification system calibration or sensor initialization using the appropriate scan tool and follow the vehicle-specific reprogram/learn procedure.
- Clear codes, perform self-tests and re-check for recurrence. Confirm proper function by observing live data and verifying passenger airbag enable/disable logic under test conditions.
Likely causes
- Connector corrosion or poor contact at seat harness under the passenger seat
- Broken or chafed signal/ground wire in the seat harness caused by seat travel
- Failed passenger occupant sensor module (internal short/open)
- Water or spilled liquid on the seat sensor mat
- Incorrect or missing occupant classification calibration after repair
Fault status
Status
Stored when the passenger occupant classification sensor circuit reports an open, short or implausible signal to the restraint control module. Code may be active, intermittent or stored pending successful completion of diagnostics and calibration.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Repair manuals
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