B10B5

Code

Generic B — Body

Body Control Module - Occupant Detection Sensor Fault

Brand: Generic

Type: B — Body

Views: UK: 8 EN: 10 RU: 9

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or disconnected occupant detection sensor (seat cushion sensor pad or mat)
Faulty connector, damaged wiring, or corrosion in harness between sensor and BCM
Poor ground or supply voltage to the sensor
Intermittent or no CAN/vehicle bus communication to BCM
Faulty Body Control Module or sensor module electronics
Software/configuration mismatch or recent module replacement without coding

Symptoms

Airbag/airbag warning lamp illuminated
Passenger airbag status message may read OFF/ON incorrectly
Seat belt reminder or passenger presence messages incorrect
DTC stored for occupant detection and possibly related communication faults
Intermittent or permanent errors after seat service or replacement

What to check

Scan all modules for codes and note freeze-frame / occurrence data
Verify vehicle electrical & airbag system safety procedures before working on seat sensors
Visual inspection of seat connectors, harness routing, and BCM connector for corrosion or damage
Check for recent seat repair, foam/cover replacement, or aftermarket accessories
Monitor live data for occupant detection status while sitting in seat and when empty
Confirm proper battery voltage and good ground(s) to BCM

Signal parameters

Sensor supply voltage: typically battery (approx. 9–14 V) or 5 V reference depending on design — verify against manufacturer spec
Sensor signal voltage/data: may be an analog voltage (0–5 V) or resistance change across sensor pads; expected idle and occupied ranges vary by vehicle
Typical seat mat resistance: tens to hundreds of ohms to kilo-ohms when occupied vs open/very high when disconnected (vehicle-specific)
CAN/ LIN: occupant sensor status messages should appear at normal bus rates (e.g., CAN 250–500 kbps); loss of message indicates bus or node issue
Diagnostic trouble code set conditions: invalid data, out-of-range value, no response from sensor node, or implausible transitions

Diagnostic algorithm

Read all stored/active DTCs and freeze-frame. Record related U- and B-codes that indicate network or module faults.
Verify and document occupant detection live data with a scan tool (sensor raw value, status bits, passenger presence). Reproduce the fault by sitting/standing on the seat and note changes.
Perform visual inspection of seat upholstery, connectors under seat, sensor pad, and wiring harness for damage, moisture, or pin corrosion.
With ignition off, disconnect the seat connector and inspect pins. Reconnect securely. Check for continuity between sensor connector and BCM connector where applicable.
Measure supply, ground, and signal at the sensor connector with ignition ON (follow SRS safety precautions). Compare voltages/resistances to manufacturer specs or expected ranges.
If sensor uses a data bus (LIN/CAN), verify communication: check for bus voltage, presence of other modules, and diagnostic messages using a capable scan tool or oscilloscope.
If wiring and power/ground are good but sensor signal out-of-range or inconsistent, swap with a known-good sensor (if available) or bench test sensor per service manual.
If sensor and harness pass but BCM still reports fault, check BCM connectors and grounds, perform BCM self-tests, and verify software/calibration. Reflash or reprogram only per OEM procedure.
Clear codes, perform functional test (seat occupied/unoccupied), and verify no recurrence. If intermittent, stress/route harness and re-check.
Follow SRS/airbag service procedures when handling seat sensors: disconnect battery and wait specified time before servicing, and ensure correct torque and connector seating when reassembling.

Likely causes

Loose or corroded connector at the seat occupant sensor
Wiring chafed where it passes through the seat or under the trim
Failed seat mat sensor (common wear point)
BCM input circuit intermittent due to water ingress or connector issue

Fault status

⚠️ Status

Body Control Module: Occupant Detection Sensor Fault — sensor data invalid, missing, or out-of-range. Check sensor, wiring, power/ground, and BCM communication.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours