B1A7B

Code

Generic B — Body

Driver Seat Occupancy Sensor Circuit Fault

Brand: Generic

Type: B — Body

Views: UK: 13 EN: 15 RU: 11

AI status

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Page language: EN

Causes

Damaged or disconnected seat occupancy sensor (seat cushion mat)
Broken, chafed or pinched wiring/harness between the sensor and control module
Corroded or loose connector pins at the sensor or module
Short to ground or short to battery in the sensor circuit
Faulty occupant detection module / body control module / SRS control module
Water/moisture intrusion into the seat cushion or connector

Symptoms

Airbag/airbag warning lamp or SRS warning lamp illuminated
Possible occupant detection warning or message on dash (seatbelt/airbag status)
Driver/airbag/passenger classification may report occupant as absent/incorrect
Intermittent or permanent inability of the system to correctly detect driver presence

What to check

Read freeze frame and stored DTCs with an OEM scanner; note freeze-frame data and related codes
Visually inspect seat cushion, upholstery, and sensor connectors for damage or contamination
Verify connectors are fully seated and locking tabs intact
Inspect wiring along seat rails and under seat for abrasion, pinching, or breaks
Check for signs of moisture inside seat and connectors
Scan for related SRS/BCM faults that may indicate shared supply/ground issues

Signal parameters

Typical occupant sensor interface is a low-voltage circuit using a 0–5 V reference — consult OEM values for your vehicle
Expected: sensor supply/reference ~5 V (or specified reference voltage) present at harness connector with ignition ON
Expected: sensor signal will change when weight/pressure applied; quiescent and occupied voltages vary by design (commonly within ~0.5–4.5 V)
Open-circuit: very high resistance or no signal present on signal pin
Short-to-ground: signal near 0 V; Short-to-B+: signal near battery voltage (~12 V) — both indicate faults

Diagnostic algorithm

Use an OEM scan tool to read DTC B1A7B and any related codes; record freeze-frame data and live PID values for the occupancy sensor circuit
Disconnect battery and follow manufacturer SRS safety procedures (wait time/disconnect steps) before working near seat airbag components
Perform a visual inspection of the driver seat cushion, sensor mat, connectors and wiring harness; look for water, corrosion, broken wires, or pinched sections
With ignition ON and using appropriate safety precautions, backprobe the sensor connector and verify reference supply voltage, signal voltage and ground presence at the harness (compare to manufacturer spec)
Perform a wiggle test: monitor live signal while moving the seat through its full travel to detect intermittent wiring faults
If wiring appears intact, measure resistance across sensor mat terminals per service manual. Replace sensor mat if resistance is out of specification or inconsistent across the element
If sensor and wiring check good, inspect/replace the seat harness connector or repair wiring as needed (use proper soldering/crimping and sealants)
If wiring and sensor are good, test or replace the occupant classification module or associated control module per OEM diagnostic flow; reprogram or calibrate if required after replacement
Clear codes and perform system checks; verify no new DTCs and that occupant detection behaves correctly (use OEM procedures to confirm)
Document repairs and advise re-checking SRS system operation and readiness indicator

Likely causes

Connector not fully seated at driver seat cushion
Wiring damaged by seat track movement or seat heater retrofit
Sensor mat degraded from moisture or wear
Control module fault less likely but possible if wiring and sensor test good

Fault status

⚠️ Status

Driver Seat Occupancy Sensor Circuit Fault — the occupant detection circuit for the driver seat is reporting an open, short, intermittent, or out-of-range signal to the control module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours