B1B90

Code

LAND ROVER B — Body

seat inclination motor relay

Brand: LAND ROVER

Type: B — Body

Views: UK: 22 EN: 24 RU: 17

AI status

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Page language: EN

Causes

Faulty seat inclination motor relay (coil or contacts)
Blown fuse or poor fuse connection in seat circuit
Open, shorted or corroded wiring/connectors between relay, seat control module and motor
Poor or missing ground at seat or relay
Seized or electrically failed seat inclination motor (overload)
Faulty seat control module or BCM driver output

Symptoms

Seat back inclination will not move or moves intermittently
Clicking noise from relay when attempting to operate seat
DTC B1B90 stored in vehicle memory
Other powered seat functions may still operate (depending on wiring)
Blown fuses in seat circuit or electrical arcing/burn marks at connectors
Possible burning smell if relay or wiring has overheated

What to check

Read and record all stored DTCs and freeze frame data with an appropriate scan tool
Visually inspect relay, fuse(s) and connector(s) related to the seat inclination circuit for corrosion, damage or loose terminals
Attempt seat operation while listening for relay click at the relay location
Check for blown fuses in the seat circuit and inspect fuse holder continuity
Inspect seat track and mechanism for mechanical binding or obstruction
Check battery voltage at the relay fuse and relay supply terminal with key on and when operating

Signal parameters

Relay coil resistance (typical): ~70–150 Ω (varies by relay design)
Relay control voltage when activated: battery voltage (~11–14 V) present at coil feed
Relay contact resistance (closed): ideally
Seat motor DC resistance (typical idle): ~0.2–3 Ω (varies by motor); very low indicates short, very high/open indicates open windings
Expected motor current (operating/stall): several amps during run; stall may draw tens of amps — ensure test equipment rated accordingly
Ground continuity:

Diagnostic algorithm

Connect a diagnostic scan tool, read and record B1B90 and any related codes. Clear codes and attempt operation to see if code returns.
Visually inspect relay, fuse(s) and harness for damage, corrosion, water ingress and loose terminals. Repair obvious issues and retest.
Check fuse(s) feeding the relay/motor for continuity and correct rating. Replace if blown and inspect for cause of failure.
With ignition on, command seat inclination and listen for relay operation. If no click, probe relay coil terminals: verify control terminal voltage (should see battery voltage when commanded) and coil resistance (relay removed) against the typical range.
If coil is energised but contacts do not pass power, measure voltage at relay output/contact to motor feed while commanding movement. If low or zero on output, replace relay.
If relay outputs battery voltage to motor but motor does not move, measure voltage at motor connector and motor winding resistance. If motor windings open or motor fails to run directly connected to battery, suspect motor failure or mechanical seizure.
Directly (bench) apply battery to the motor (observe safety — use an ammeter and proper precautions) to check motor operation and current draw. Excessive current indicates mechanical binding or internal motor fault.
Check grounds and continuity between relay, seat motor and seat control module. Repair any high resistance or intermittent connections.
If wiring and motor test good, verify control output from the seat control module/BCM using the scan tool or a lab scope. If the control module does not command the relay correctly, consider module fault or programming issue.
After repairs, clear codes, re-test seat operation through full range and road-test if required. Monitor for code reoccurrence.

Likely causes

Relay coil open or relay contacts welded/sticking
Corroded/loose connector at relay or seat motor harness
Blown/poor fuse supplying the relay or motor
Short to ground or to battery in motor feed circuit causing overload and relay fault
Motor partially seized causing excessive current and relay trip/failure

Fault status

⚠️ Status

B1B90 — Seat inclination motor relay circuit fault detected. Relay, fuse, wiring, ground, seat motor or control module may be defective or have an intermittent connection.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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