B0157

Code

Generic B — Body

Front Passenger Occupant Detection Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 14 EN: 16 RU: 17

AI status

Completed

ready

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Page language: EN

Causes

Damaged or chafed wiring in the occupant detection harness
Corroded, loose or disconnected connector at the sensor or control module
Faulty occupant detection sensor (seat mat/sensor module)
Faulty passenger airbag/occupant classification module or ECU
Water intrusion or contamination in the seat area or connector
Aftermarket seat covers, heater elements or repairs interfering with the sensor

Symptoms

Passenger airbag status unavailable or incorrect (airbag may be disabled)
Passenger airbag or SRS warning light illuminated on dash
Passenger seatbelt reminder or indicator behaves incorrectly
Inability to arm/disarm passenger airbag or system fault messages
Intermittent changes in passenger detection status when occupant moves or seat is adjusted

What to check

Read and record B0157 and any related stored codes and freeze frame data with an OBD-II/SRS-capable scan tool
Inspect passenger seat area for dampness, contaminants or aftermarket covers that could affect the sensor
Visually inspect connectors, wiring and seat harness for damage, corrosion, pin push-out, or loose latches
Verify fuses and power supplies to the occupant module as specified by the vehicle service manual
If available, view live data/parameter for the passenger detection sensor or occupant classification status while someone sits and moves on the seat

Signal parameters

Sensor signal: typically a low-voltage signal reported to occupant module (expected range 0.0–5.0 V depending on manufacturer)
Reference voltage to sensor: commonly 5 V or regulated reference from occupant module (check vehicle spec)
Ground continuity:
Resistance/impedance of seat mat sensor (if specified by maker) — compare to service manual values
CAN/LIN communication: module should report presence/ID on vehicle network (if applicable)

Diagnostic algorithm

Establish symptoms and capture freeze frame, related B-codes and live data with an SRS-capable scan tool. Note when the fault sets (seat occupied/unoccupied, seat position).
Perform visual inspection of the passenger seat, connectors under seat, and harness along seat rails for damage, water, corrosion or pin damage. Repair or reseat connectors as needed. Follow SRS safety procedures (battery disconnect or recommended measures) before working near airbag components.
With connector disconnected, inspect pins and sockets for corrosion, bending or pushed-out pins. Reconnect and check for improved fault status.
Backprobe the sensor connector with the ignition ON and check for specified reference voltage, signal voltage and ground continuity. Compare values to vehicle specifications (expected reference ~5 V, signal within 0–5 V).
Wiggle the harness and move the seat while watching live data or DTC status to identify intermittent wiring breaks or shorts.
If signal/reference are out of range or open/shorted, trace and repair wiring harness to module. Repair or replace damaged wiring or connectors.
If wiring and connectors are good, test or replace the passenger occupant detection sensor (seat mat/module) per manufacturer procedure. Some sensors require calibration after replacement.
If sensor and wiring test good but fault persists, inspect occupant classification/airbag control module and related network communication. Replace module only after confirming upstream sensors and harness are good.
Clear codes, perform required sensor/module calibrations, and retest system through several occupancy scenarios to confirm repair.

Likely causes

Loose/disconnected connector at passenger seat sensor
Open or shorted wiring between the seat sensor and occupant module
Failed occupant detection sensor module (seat mat)
Corroded connector or water-damaged sensor harness

Fault status

⚠️ Status

Front passenger occupant detection sensor circuit malfunction — open/short/intermittent signal or out-of-range reading detected. May cause passenger airbag to be disabled or SRS warning lamp to illuminate.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours