B1A5B

Code

LAND ROVER B — Body

backrest of driver's seat sensor failure

Brand: LAND ROVER

Type: B — Body

Views: UK: 6 EN: 6 RU: 3

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Page language: EN

Causes

Open or short circuit in sensor wiring or connector
Failed backrest position sensor (potentiometer/Hall-effect unit)
Corroded or loose connector contacts
Faulty seat control module or software/firmware error
Intermittent wiring damage from seat movement
Faults caused during previous seat removal/installation (pinched wires)

Symptoms

DTC B1A5B stored in body/seat control module
Driver's seat backrest position not displayed or incorrect on cluster/infotainment
Seat memory or position functions (if equipped) not working reliably
Intermittent or fixed fault indicator related to seat adjustment
Possible impact on airbag/seatbelt pretensioner logic if tied into occupant detection systems

What to check

Read and record stored and pending DTCs with a capable scan tool (seat/body modules). Check freeze frame and event data.
Verify whether the fault is permanent or intermittent by cycling the seat and checking live data while moving the backrest.
Visually inspect seat wiring harness, connectors and sensor mounting for damage, corrosion or deformation.
Wiggle harness and connectors while monitoring live sensor values to reproduce the fault.
Check for related codes in SRS/airbag and body modules that might indicate shared wiring or ground issues.
Confirm battery voltage is stable during testing (low voltage can cause sensor errors).

Signal parameters

Sensor type: typically an analog potentiometer or Hall-effect position sensor (angle/position output).
Expected behavior: smooth, continuous change in signal as backrest is moved; no sudden jumps or dropouts.
Typical voltage range (manufacturer-dependent): approximately 0.1–4.9 V for analog sensors (verify with service data).
Resistance: potentiometer-type sensors normally show smoothly varying resistance across travel (consult service manual for values).
Communication: some systems report position over a local BUS to the seat module; check for valid CAN/LIN messages if applicable.

Diagnostic algorithm

Connect a diagnostic tool that can read the seat/occupant module. Retrieve all fault codes and live data related to the driver's seat backrest sensor.
Note the sensor live values. Slowly move the backrest through full travel while watching the signal for smoothness, expected range, and repeatability.
Perform a visual inspection: remove trim as needed to access the backrest sensor connector and wiring. Look for chafing where wires pass the hinge or frame.
With ignition on and connector disconnected, check for reference voltage and ground at the sensor connector using a DVOM. Compare to service specification.
Measure sensor output at the connector while operating the backrest. For a potentiometer, verify voltage changes smoothly; for Hall sensors, verify voltage or resistance per manual.
If intermittent, perform wiggle tests on the harness and connector while monitoring output. Repair or secure any damaged wiring found.
If wiring and connector check good, bench-test or replace the backrest sensor per manufacturer procedure. If replacing, observe anti-static/handling and mechanical adjustments.
If sensor and wiring are good, inspect seat control module grounds and supply voltages. Swap with known-good module only if supported by manufacturer procedures.
After repairs, clear DTCs and perform functional check: cycle seat, confirm live data correct and that code does not return. Perform any required seat module recalibration or coding.
If fault persists, consult Land Rover service data for module-specific diagnostics and wiring diagrams; consider dealer-level support for body module reprogramming.

Likely causes

Broken/abraded cable in the harness where it passes through the seat frame
Water ingress or corrosion at the backrest sensor connector
Wear or mechanical failure of the sensor element inside the backrest
Connector not fully mated after seat work
Seat module reporting due to internal fault (less common)

Fault status

⚠️ Status

Driver's seat backrest sensor failure — control module detects invalid or missing backrest position signal (out-of-range, erratic or no communication).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0–3.0 hours

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B1A5B — backrest of driver's seat sensor failure