B119A

Code

LAND ROVER B — Body

Front Passenger Occupant Detection Sensor Circuit - Implausible Signal

Brand: LAND ROVER

Type: B — Body

Views: UK: 17 EN: 26 RU: 21

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Page language: EN

Causes

Damaged or corroded connector or wiring between occupant sensor and restraint control module (RCM)
Faulty passenger occupant detection mat/sensor module
Poor or missing ground or supply voltage to the sensor
Moisture/contamination, seat foam damage or foreign objects affecting the sensor mat
Interference from aftermarket seat covers or heating elements
Faulty RCM or seat occupancy control module (rare)

Symptoms

Airbag warning lamp illuminated
Passenger airbag disabled or not deploying per occupant classification
Message on dash indicating passenger seat fault or passenger airbag unavailable
Seatbelt reminder behaves incorrectly for passenger seat
DTC B119A (and possibly related B‑codes) stored in SRS/airbag module

What to check

Read and record SRS/airbag module trouble codes and freeze-frame data with an appropriate scan tool
Visually inspect passenger seat, underside and connector areas for damage, contamination or foreign objects
Check fuses and main power/ground feeds for the airbag/passenger detection circuit
Wiggle test wiring and connectors while monitoring live sensor data for intermittent faults
Check for recent seat repairs, replacements or aftermarket seat covers/heaters

Signal parameters

Sensor supply: typically a regulated reference (often 5 V) — verify presence at connector with key ON (consult vehicle-specific data)
Ground: low resistance to chassis ground (< 1 ohm typical) at sensor ground terminal
Signal output: typically a varying voltage or impedance that changes with occupant presence — should be stable and change predictably when weight is applied/removed (0–5 V range is common; consult vehicle-specific values)
Continuity/resistance: sensor mat elements normally show measurable continuity/impedance; open or wildly fluctuating resistance indicates a failed mat
Communication: some systems use a seat module communicating over CAN/LIN — verify bus messages if applicable

Diagnostic algorithm

Connect an SRS-capable scan tool. Read and record B119A and any related SRS/seat module codes. Note freeze frame and live data for passenger occupant sensor.
Verify vehicle battery voltage is normal and key is in required position for tests. Do not deploy airbags or work on live SRS circuits without following safety procedures.
Visually inspect the passenger seat (top, underside, rails) and the occupant sensor connector for corrosion, bent pins, water intrusion, or contamination. Remove trim as needed to access connectors.
Check fuses and power/ground to the seat/occupant sensor circuit. Backprobe the sensor connector: verify reference supply voltage (eg. ~5 V), good ground, and presence of a signal wire. Compare to expected/known-good values.
With the scan tool monitoring live data, apply and remove weight to the passenger seat (use a calibrated test weight or have a helper sit briefly). Observe that the sensor output changes predictably and the module updates occupant status. If signal is erratic or implausible, proceed.
Perform continuity and resistance checks on wiring between sensor and RCM/module with connectors disconnected. Inspect for opens/shorts to ground or battery. Wiggle wiring harness along seat travel to try to reproduce fault.
If wiring and connectors test good, test the sensor mat per manufacturer procedure (resistance/impedance or bench test). Replace sensor mat if out-of-spec or intermittent.
If sensor and wiring are good but fault persists, check for module software updates and reprogram/calibrate the passenger detection system per manufacturer service procedures after any replacement.
Clear codes and perform a full seat occupancy verification cycle; retest road or as required. If code returns, consider replacing the occupant detection sensor/module or consult dealer-level diagnostics for RCM faults.
After repair, ensure proper recalibration/initialization of the occupant detection system and confirm normal operation and that no SRS lights persist.

Likely causes

Open/short in signal/ground/supply wires under the seat (wear from seat adjusters)
Connector corrosion or bent/pushed pins at sensor or RCM connector
Sensor mat element failure (intermittent or out-of-range resistance/impedance)
Contamination (water, spilled liquid) creating unpredictable sensor readings

Fault status

⚠️ Status

Front Passenger Occupant Detection Sensor Circuit — Implausible Signal. Passenger occupant classification may be unavailable; SRS module has detected an invalid or inconsistent sensor signal.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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B119A — Front Passenger Occupant Detection Sensor Circuit - Implausible Signal