B29D2

Code

Generic B — Body

Passenger occupant detection sensor circuit high

Brand: Generic

Type: B — Body

Views: UK: 11 EN: 16 RU: 12

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Page language: EN

Causes

Short to battery or other high voltage source on the sensor signal wire
Failed occupant detection sensor (seat mat or sensor module)
Corroded/loose connector or terminal at the sensor or airbag control module
Damaged or chafed wiring harness (shorts, pinched wires)
Poor or missing sensor/module ground
Water or contamination in the seat mat or connector

Symptoms

SRS/Airbag warning lamp illuminated
Passenger airbag status message may show disabled or unavailable
Passenger presence indicator incorrect (shows occupied when empty or vice versa)
Possible inability to arm or deploy passenger airbag until fault cleared
Diagnostic trouble code B29D2 stored in SRS module

What to check

Use a scan tool to read SRS/occupant classification live data and confirm B29D2 and any additional codes
Visually inspect seat bottom, seat rails, connectors under the seat, and wiring harness for damage or contamination
Disconnect battery and inspect connectors for corrosion, bent pins, or pushed-out terminals
With ignition on, measure the sensor signal voltage at the connector (compare to reference and to values with known occupant states)
Perform continuity and short-to-voltage/short-to-ground checks on the sensor signal and power/ground circuits
Wiggle test wiring and connectors while monitoring live data to reproduce intermittent faults

Signal parameters

Reference/sensor supply typically a low-voltage reference from SRS module (commonly in the 0–5 V range)
Normal sensor signal: depends on system and occupant condition; usually well below the supply (example nominal ranges vary by manufacturer)
‘High’ condition: sensor output above the expected maximum or near supply voltage (often >4.5 V) or a diagnostic ‘open/high’ reading reported by module
Resistance of a functioning seat mat varies by design; manufacturer service data required for exact ohms

Diagnostic algorithm

Retrieve all SRS/occupant-related codes and freeze-frame data with an appropriate scan tool; record live data for the occupant sensor circuit. 2) Visually inspect the seat, mat, connectors, and harness for damage, corrosion, or contamination; remove debris and dry any moisture. 3) With battery connected and ignition on (follow safety procedures for SRS systems), backprobe the occupant sensor connector and measure signal voltage and supply/reference voltage. Compare to manufacturer specifications. 4) Check continuity between the sensor ground and chassis ground and between the sensor signal and the SRS module input; check for short to battery using an ohmmeter (with power removed). 5) Perform a wiggle/seat-movement test while watching live data to identify intermittent wiring faults. 6) If wiring and connectors test good, disconnect the sensor and measure open-circuit behavior; replace the seat mat/sensor module if it fails bench or resistance checks. 7) If the sensor and wiring check good, consider replacing or reprogramming the SRS/occupant classification module per service manual. 8) After repairs, clear codes, perform any required calibration/occupant sensor learning procedure, and verify the fault does not return.
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Likely causes

Short to battery voltage on the signal circuit
Defective seat occupant detection mat/module
Connector corrosion or poor pin contact
Wire damage near seat hinges or rails
Contamination (water) in the sensor mat causing abnormal readings

Fault status

⚠️ Status

Passenger occupant detection sensor circuit HIGH detected. Sensor output is above expected range or reporting an open/high condition. May cause passenger airbag to be disabled and SRS lamp to illuminate.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours