Code
B1019
HUMMER
B — Body
Occupant Classification Sensor Circuit Fault
AI status
Completed
Completed
100%
Causes
- Broken, chafed or corroded wiring or connector to the occupant classification sensor
- Poor or intermittent connector seating (corrosion, bent pins, water intrusion)
- Faulty occupant classification sensor (mat or module under seat)
- Faulty restraint control module or internal driver electronics
- Aftermarket seat covers, foam replacement, or foreign objects interfering with sensor mat
- Damage from seat removal/installation or seat heater repairs
Symptoms
- Airbag readiness light or SRS indicator may illuminate
- Passenger airbag enable/disable status incorrect or changing
- Possible disablement of passenger airbag depending on system logic
- DTC stored and may be current or intermittent
- No other drivability symptoms typically caused by this fault
What to check
- Read and record all SRS/airbag DTCs and freeze frame data with a compatible scan tool
- Visual inspection of seat cushion, seat track area and occupancy mat connectors for damage or contamination
- Inspect wiring harness for chafing, pinched areas or previous repair sections under the seat
- Verify proper seating of connectors; check for bent or pushed‑out pins
- Check for aftermarket seat covers or items placed on the seat that could affect mat performance
- Perform wiggle test while monitoring live OCS data for intermittent changes
Signal parameters
- Reference (supply) voltage to OCS typically 5 V (check service manual for exact value)
- OCS signal voltage expected in a valid range (typically between ~0.5 V and ~4.5 V depending on occupancy and design)
- Short to ground: signal ≈ 0–0.3 V; short to battery: signal ≈ supply voltage (≈4.7–5 V)
- Open circuit: signal may be floating or undefined; diagnostic tool may show 'no response' or extreme values
- Expected continuity/resistance of mat and harness per manufacturer specifications (consult service data)
Diagnostic algorithm
- Retrieve all related SRS/airbag codes with a capable scan tool and note freeze frame/live data for OCS.
- Consult the vehicle service manual for manufacturer‑specific OCS test values, wiring diagrams and connector pinouts.
- Visually inspect the passenger seat cushion, seat back, connector, and wiring for damage, corrosion, water entry, or aftermarket alterations. Repair obvious damage.
- With ignition ON (follow SRS safety procedures), monitor the OCS live data while observing connector seating and while performing a gentle wiggle on the harness to check for intermittent faults.
- Measure reference voltage and ground at the OCS connector; verify sensor supply (≈5 V) and ground integrity.
- Measure the OCS signal voltage at the sensor and at the restraint control module connector; compare pin‑to‑pin. Look for short to battery/ground or open circuit.
- If guided by service data, measure mat resistance or perform manufacturer OCS mat resistance test. Replace mat if out of spec or damaged.
- If harness faults are found, repair or replace wiring and connectors, then retest. If wiring is good and sensor still fails, replace the occupant classification sensor/module.
- After repairs, clear codes, perform any required OCS or SRS calibration/relearn procedure with the appropriate scan tool, and verify the code does not return.
- If the code persists after sensor replacement and harness checks, test or replace the restraint control module according to factory procedures.
Likely causes
- Open circuit or short to battery/ground in the seat occupancy mat harness
- Contaminated or pushed‑out pin in seat cushion connector
- Moisture ingress into the sensor mat or connector
- Defective occupant classification sensor module (age, impact or physical damage)
- Improper seat reassembly or non‑OEM seat components changing sensor readings
Fault status
Status
Stored when the restraint control module detects an out‑of‑range, open, shorted or intermittent occupant classification sensor circuit. May be active or intermittent; can affect passenger airbag enable/disable logic.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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