B1C1B

Code

Generic B — Body

Passenger seat occupant classification sensor circuit — high voltage

Brand: Generic

Type: B — Body

Views: UK: 12 EN: 18 RU: 19

AI status

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Page language: EN

Causes

Short to battery voltage on the occupant classification sensor signal or power circuit
Faulty occupant classification sensor (seat pad/mat module) producing an out‑of‑range voltage
Damaged or chafed wiring harness or connector causing intermittent/solid high voltage
Poor or missing ground at sensor or control module causing abnormal readings
Faulty occupant classification / airbag control module (rare)
Contamination (moisture, corrosion) in seat sensor connector or seat cushion sensor

Symptoms

Airbag warning light illuminated; occupant classification system fault stored
Passenger airbag status indicator may display incorrectly (ON/OFF unpredictable)
Possible disablement of passenger airbag or error message on dash
Diagnostic trouble code B1C1B stored in occupant classification / SRS module
Vehicle may require occupant classification system relearn after repair

What to check

Read and record all stored SRS/occupant-classification codes and freeze-frame data with a capable scan tool
Inspect seat cushion, connectors, harness, and routing for visible damage, moisture, or pin corrosion
Visually inspect and wiggle harness while monitoring live data to reproduce high-voltage condition
Check for other related codes in SRS or body control modules
Verify service/disconnection procedures for the airbag system before any hands-on work (battery disconnect and wait per manufacturer)

Signal parameters

Reference supply to sensor: typically 5 V nominal (vehicle-specific)
Expected signal range: approx. 0–5 V for most occupant sensors (vehicle-specific)
High-voltage fault threshold: signal higher than specified reference (varies by manufacturer; often >5.5 V or detection of >reference)
Ground: low resistance to chassis ground; continuity expected

Diagnostic algorithm

Safety first: disable SRS power per manufacturer procedure (disconnect battery and wait specified time) before removing seat or connectors
Scan tool: retrieve codes, freeze-frame, and live data for passenger occupant sensor. Note conditions when code set.
Visual: inspect seat cushion, sensor mat, wiring harness, connectors and pin condition. Look for water intrusion, rodent damage, chafed insulation, or bent pins.
Backprobe with battery reconnected and SRS enabled only if trained: measure sensor supply (reference) and sensor signal at the occupant classification connector with a digital multimeter. Reference should be approx. 5 V; signal should be within expected range. A signal above the reference or above the manufacturer’s max indicates high-voltage condition.
Check for short-to-power: with ignition on, use a multimeter to check for voltage on the signal wire at the module and at the sensor. If the signal shows battery voltage or near battery voltage at rest, trace wiring for short to +B.
Check grounds: measure continuity/resistance from module and sensor ground to chassis ground. Repair high resistance/poor grounds.
Wiggle test: move seat cushions and harness while watching live data to reveal intermittent shorts or opens.
If wiring checks good and connector pins are clean and secure but high voltage remains, replace the passenger seat occupant classification sensor (seat pad/module) and retest.
If replacement sensor does not clear fault, consider replacement or reprogramming of occupant classification / airbag control module as directed by manufacturer diagnostics.
After repair, clear DTCs, verify no reoccurrence, and perform any required occupant classification system relearn or calibration procedures.
Note: always follow vehicle manufacturer SRS precautions. Do not probe pyro devices or airbag initiator circuits.

Likely causes

Wiring short to +B (battery) on the passenger seat sensor signal or supply feed
Defective passenger seat occupant classification sensor (seat cushion pad/module)
Corroded/loose connector or pin pushed out at seat harness or module
Ground connection missing or high resistance at occupant classification module

Fault status

⚠️ Status

Passenger seat occupant classification sensor circuit — high voltage. The occupant classification/airbag control module has detected signal voltage from the passenger seat sensor that exceeds the expected range. Airbag deployment logic for the passenger seat may be affected until repaired.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3 hours