B1C7B

Code

Generic B — Body

Occupant Classification Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 5 EN: 9 RU: 7

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or corroded connector(s) at the occupant classification sensor (seat cushion/seat module)
Broken, pinched or shorted wiring harness under the seat
Poor ground or missing reference voltage to the sensor
Water intrusion, contamination or physical damage to the sensor mat/module
Aftermarket seat covers, repairs or seat foam changes interfering with the sensor
Faulty occupant classification sensor module or seat control module

Symptoms

SRS/AIRBAG warning lamp illuminated
Passenger airbag disabled or unexpected passenger airbag status message
Unable to detect or incorrectly classify occupant on front passenger seat
DTC present only when seat is occupied or after a seat position change
Intermittent fault or lamp that returns after clearing codes

What to check

Use a scan tool to read fault (and any related SRS/seat module codes) and capture freeze frame/live data
Visually inspect seat upholstery, connectors and wiring harness under the seat for damage, corrosion or loose pins
Check for aftermarket seat covers, foam or repairs that could compress or damage the sensor mat
Verify battery voltage and SRS system power/grounds before testing
Follow OEM SRS safety procedures (battery disconnect and specified wait time) before disconnecting harnesses or removing the seat
Perform wiggle tests on seat wiring while monitoring live data for intermittent changes

Signal parameters

Reference supply typically provided by SRS/seat module (commonly 5 V reference) — verify present at sensor connector
Signal line often a low-voltage analog or digital frequency/voltage proportional to mat load; should change between empty and occupied
Ground continuity to vehicle chassis/seat module ground — near 0 ohms expected
Module communication (if applicable) over LIN/CAN to restraint module — messages typically periodic (e.g., multiple Hz); loss of communication may set faults
Open-circuit or short-to-ground/short-to-VBAT will produce diagnostic thresholds in the SRS module

Diagnostic algorithm

Read and record all SRS/seat module DTCs and freeze frame data with a capable scan tool. Note when the code sets (occupied/unoccupied, seat position).
Inspect the passenger seat area: upholstery, sensor mat, connectors, and wiring for obvious damage, moisture or aftermarket modifications.
Follow the manufacturer's SRS safety procedure: disconnect battery and wait required time before performing in-seat electrical work.
With harness disconnected, inspect connector pins for corrosion, bent pins or debris. Clean and repair as needed.
Reconnect battery per procedure (if required for live measurements). Backprobe the sensor connector and verify reference voltage, signal voltage change between empty and occupied, and ground integrity with a multimeter/oscilloscope. Record values.
Perform continuity and resistance checks between the sensor connector and seat/module/RCM pins to locate opens or high resistance.
Wiggle the seat wiring and connectors while monitoring live data to reproduce intermittent faults. Check for changes in signal and for corresponding DTC set/clear events.
If wiring and connectors test good, test or replace the occupant classification sensor module (or swap with known-good unit if available) and re-check system operation.
After repairs, clear codes and verify the system does not return to fault under normal seat conditions. Confirm passenger airbag enable/disable behavior is correct.
If fault persists and wiring and sensor are good, consider replacing or reprogramming the seat module or restraint control module per OEM procedures.

Likely causes

Open or short in signal/reference/ground circuit between sensor and airbag/seat module
Intermittent connection due to corroded connector or broken wire under seat
Sensor mat damaged by moisture or sharp object
Defective occupant classification sensor module