B1C75

Code

Generic B — Body

Passenger Presence Sensor Circuit Malfunction

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 7 RU: 11

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Page language: EN

Causes

Open or shorted wiring between passenger presence sensor and SRS module
Damaged or contaminated sensor/seat cushion mat (force-sensing resistor or capacitive pad)
Corroded or loose connector(s) under the seat
Water/moisture intrusion in seat or connector
Poor ground or power supply to the sensor
Faulty SRS/airbag control module or internal electronics

Symptoms

SRS/Airbag warning lamp illuminated
Passenger airbag disabled when seat is occupied, or enabled when empty
Passenger occupancy indicator incorrect or toggling
Seat belt reminder behavior may be incorrect
Possible stored additional SRS-related codes

What to check

Use a scan tool to read DTC B1C75 and any related SRS codes; record freeze frame and live data for passenger presence sensor
Visually inspect seat area: connectors, harness routing, zip-ties, seat tracks for chafing or damage
Check for water or contamination on or under the seat cushion and connector areas
Wiggle the seat and harness while monitoring live sensor data to look for intermittent changes
Confirm seat covers or objects are not preventing proper sensor operation
Verify battery voltage and proper ground(s) to the SRS module before tests

Signal parameters

Reference supply from SRS module typically ~5 V (verify exact value in service manual)
Sensor signal is a variable voltage proportional to occupancy — typically ranges between ~0.2 V and ~4.8 V (manufacturer-specific)
Open-circuit or short conditions often read as infinite resistance or near 0 V / battery voltage on the signal line
Resistance of force-sensing mats varies with load; expect measurable change when weight is applied vs. empty (use manufacturer values when available)
Observe live-data passenger presence status (occupied/empty/unknown) while applying and removing weight

Diagnostic algorithm

Safety: follow SRS safety procedures. Disable SRS power per manufacturer (disconnect battery and wait specified time) before disconnecting connectors or working near inflators.
Use a scan tool to confirm B1C75 and note any related SRS codes and live-data values (sensor voltage, occupant status, freeze frame).
Perform a visual inspection of the passenger seat, underside cushion, connectors, and wiring harness for damage, corrosion, or contamination.
With power reconnected and scanner monitoring live data, wiggle the seat and harness and observe for intermittent changes in sensor voltage or occupancy status.
Measure reference voltage and signal at the sensor connector while following safety guidance. Compare readings to service manual limits. Check for shorts to ground or battery.
If available, perform an active test or bench test of the sensor module per manufacturer procedures (or replace suspect connector harness and re-test).
If wiring and connectors test good, perform resistance/continuity checks from sensor connector to SRS module pins to locate opens or shorts.
Inspect for moisture/damage in the seat cushion mat. If the mat is damaged or contaminated, replace the mat or the entire seat cushion assembly as specified.
If repairs are made (connector repair, harness replacement, sensor/mat replacement), clear codes and follow any required occupant classification calibration or initialization procedures.
Verify repair by confirming fault does not return and passenger occupancy status behaves correctly under normal conditions.

Likely causes

Damaged/loose connector or wiring under the passenger seat (pin damage, chafe, corrosion)
Damaged or contaminated passenger presence sensor mat (wear, puncture, moisture)
Intermittent wiring fault caused by seat movement (broken conductor in flex harness)
Sensor harness shorted to ground or battery voltage
Faulty SRS control module (less common)