Code
B3182
HUMMER
B — Body
Occupant Classification System Sensor — Performance Fault
AI status
Completed
Completed
100%
Causes
- Damaged or shorted OCS sensor element(s) in the seat cushion.
- Poor electrical connection: corroded/damaged connector, broken wire, or pin-backout in seat harness.
- Open or high-resistance ground or power supply to the sensor/module.
- Seat cushion contamination, moisture or foreign material affecting sensor response.
- Faulty Occupant Classification Module (seat control module) or software anomaly.
- Recent seat repair, replacement or improper reassembly causing misrouting of wiring or incorrect sensor installation.
Symptoms
- Airbag/airbag indicator lamp illuminated or a related SRS/OCS warning displayed on the dash.
- Seat belt/airbag system may disable passenger airbag (PASS AIRBAG OFF) incorrectly.
- Diagnostic trouble code B3182 stored in the airbag/seat module memory.
- Possible erratic or inconsistent occupant classification messages (passenger present/not present).
What to check
- Read and record all stored SRS/OCS codes and freeze frame data with an appropriate scan tool.
- Inspect Service Bulletins or calibration updates for the specific model and model year before repairs.
- Visually inspect the seat cushion and underside for moisture, damage, or foreign objects.
- Visually inspect connectors and wiring between OCS sensors and the seat/airbag module for damage, corrosion, pin damage, or poor seating.
- Perform wiggle test on seat harness/connectors while monitoring live OCS sensor data for intermittent changes.
- Verify power and ground at the seat control module and OCS sensor connector with key on (refer to vehicle wiring diagram).
Signal parameters
- Sensor supply voltage: typically 5 V reference (expected ≈4.75–5.25 V) — verify against vehicle-specific data.
- Sensor signal voltage: analog output typically varies with load; expect a stable voltage within ~0.5–4.5 V range that changes smoothly with applied weight.
- Return/ground continuity: near 0 Ω to chassis ground (low resistance).
- CAN/LIN bus activity: if the OCS interfaces via network, bus should be active and error-free (no bus-off).
- Diagnostic tool: live OCS sensor ADC counts or kg reading should change logically and smoothly with applied weight.
Diagnostic algorithm
- Connect a capable SRS/diagnostic scanner and read all codes and freeze-frame data. Note which seat position/sensor is identified.
- Review manufacturer service information and TSBs for procedures, calibration steps, or module software updates related to OCS.
- Visually inspect the seat cushion and underside for contamination or damage. Remove seat trim if needed for access, following SRS safety procedures (battery disconnect where required).
- Inspect connectors and wiring for damage, corrosion, pin distortion or poor retention. Repair any damaged wiring with proper methods (splice/replacement per factory recommendations).
- With ignition ON and scanner on live data, observe the OCS sensor output. Perform a wiggle test on the harness/connectors and seat adjustment mechanisms to check for intermittent faults.
- Measure supply and ground at the sensor connector. Confirm reference voltage and ground integrity. Repair if out of specification.
- Measure sensor signal while applying a known weight or load to the seat cushion and observe expected smooth change in voltage or classifier values. Compare to vehicle-specific expected behavior.
- If wiring and sensor signals are within specification but values are implausible or module reports inconsistent sensor performance, perform module self-test, recalibration, or occupant classifier calibration per manufacturer procedure.
- If a sensor is confirmed defective, replace the OCS sensor or the seat cushion subassembly as recommended by the manufacturer. Ensure correct part and orientation.
- After repair or replacement perform required OCS recalibration/initialization and clear codes. Recheck for DTC return and verify system operation with live data and functional tests.
- If code persists after sensor replacement and calibration, consider seat control module replacement or professional diagnostics of module and network communications.
Likely causes
- Damaged sensor element or connector in the affected seat.
- Corroded or loose connector at the OCS sensor or seat control module.
- High-resistance ground or supply failure to the OCS sensor.
Fault status
Status
Occupant Classification System sensor output is outside expected performance parameters; the seat/airbag module has flagged an OCS sensor performance fault.
Repair difficulty: Hard
Diagnostic time: 1.5-3.0 hours
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