B0732

Code

Generic B — Body

Occupant Classification Sensor Circuit Fault — Short/Open

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 14 RU: 12

AI status

Completed

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Page language: EN

Causes

Damaged or disconnected seat occupancy sensor (mat)
Broken, chafed, or pinched wiring harness or connector to the sensor
Corroded or contaminated connector terminals
Short to ground or battery voltage in the sensor circuit
Faulty occupant classification ECU/module
Moisture or foreign material inside seat sensor mat (water intrusion)

Symptoms

Airbag/OCC indicator or SRS warning lamp illuminated on dash
Occupant classification system disabled — passenger airbag may be forced off or on incorrectly
Possible logs of related B-codes for occupant sensor circuits
Loss of passenger presence detection or incorrect passenger status message
Possible intermittent faults when seat is moved or when weight placed on seat

What to check

Read DTCs and freeze frame data with a capable scan tool and note history and related codes
Visually inspect seat cushion area, connectors under seat, and harness routing along seat rails for damage, pinching, corrosion, or water intrusion
Check connector mating condition and look for bent/pushed pins or foreign debris
Perform wiggle test on harness and connectors while monitoring live data/scan tool for changes
Measure reference voltage and signal at the sensor connector with ignition ON (per manufacturer values)
Check continuity between sensor and ECU and inspect for shorts to ground or battery

Signal parameters

Typical system reference: 5 V reference from OCC ECU (verify with OEM spec)
Open circuit: signal shows OL/infinite resistance or sensor voltage ~0 V (or no signal)
Short-to-ground: signal ~0 V; short-to-battery: signal ≈ battery voltage (~12 V)
Expected seat sensor signal voltage varies by weight — normally in the mid-range (approx. 0.2–4.8 V) depending on occupant; check OEM chart for exact ranges
Typical DC resistance of a healthy mat varies by design—compare measured resistance to OEM spec

Diagnostic algorithm

Record all stored and pending DTCs and freeze-frame values; note any related occupant classification or SRS codes.
With ignition ON (engine off), inspect the seat cushion area and under-seat connectors for visible damage, moisture, or loose connectors; reseat connectors.
Access the occupant sensor connector; check for corrosion, bent pins, or foreign material. Clean and apply dielectric grease if required.
Perform a wiggle test while monitoring live signal/diagnostic data: move seat forward/back and manipulate harness to reproduce fault or intermittent behavior.
Measure reference voltage at the sensor connector (verify ~5 V reference per OEM). If reference absent, suspect ECU or blown fuse.
Measure signal voltage at connector with no load (seat empty) and with known weight; look for open (OL) or fixed 0 V/12 V indicating short.
Measure resistance across sensor mat terminals per OEM procedure; compare to spec. An open or out-of-spec resistance indicates a faulty mat.
Check continuity from sensor connector to occupant classification ECU pins; check for short to ground or battery with ohmmeter/voltmeter.
If wiring and connectors pass, suspect faulty occupant sensor mat or occupant classification ECU. Replace faulty component as indicated by tests.
After repair, clear codes and perform system calibration/occupant presence learning per manufacturer procedure; verify no return of B0732.

Likely causes

Disconnected or loose seat cushion connector (common after seat service)
Wire damaged by seat movement (belt buckle, rails) causing open or intermittent short
Connector pins pushed back or bent allowing poor contact
Sensor mat degraded or torn allowing moisture penetration and internal short
ECU internal fault or failed voltage reference

Fault status

⚠️ Status

Occupant Classification Sensor Circuit Fault — Short or Open detected. Electrical fault in seat occupant sensor circuit; may disable passenger detection and affect airbag control.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours