B1229

Code

LAND ROVER B — Body

Left rear seat temperature sensor

Brand: LAND ROVER

Type: B — Body

Views: UK: 21 EN: 22 RU: 30

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Page language: EN

Causes

Open or shorted wiring in the left rear seat temperature sensor circuit
Loose, corroded or disconnected connector at the sensor or seat module
Failed temperature sensor (thermistor) in the left rear seat
Faulty seat control module or comfort module
Water ingress or physical damage to the seat harness or sensor
Software or communication error on the bus (CAN/LIN)

Symptoms

Stored B1229 fault code and possible related warnings on the instrument cluster or infotainment screen
Left rear seat temperature/heating/cooling zone not regulating correctly or inoperative
Occupant temperature reading for that seat incorrect or unavailable in diagnostics/live data
Possible reduced comfort control for rear left zone

What to check

Use a diagnostic scanner to read DTCs, freeze frame and live data for seat temperature sensors and related modules
Visually inspect the left rear seat: connectors, wiring harness, and visible sensor for damage, corrosion or water
Check for other related codes that indicate module or bus communication faults
With ignition on, backprobe the sensor connector and measure reference voltage and signal (or resistance) per service data
Perform a wiggle test on the harness and connectors while monitoring live data for intermittent changes
Inspect seat module grounds and supply fuses

Signal parameters

Sensor type: typically an NTC thermistor (resistance changes with temperature)
Expected electrical behavior: resistance decreases as temperature increases (negative temperature coefficient)
Common signal interface: voltage divider or direct resistance reading to module; signal range typically within 0–5 V or measured as kiloohms across sensor terminals—refer to factory data for exact values
Fault condition examples: open circuit (infinite resistance), short to ground (near 0 Ω), or signal out-of-range voltage

Diagnostic algorithm

Connect a manufacturer-level scan tool and record DTC(s), freeze-frame and live data for the left rear seat temp sensor and seat module communications.
Visually inspect the left rear seat area, connectors and wiring for damage, corrosion or evidence of water ingress. Repair visible damage before retest.
With ignition on, backprobe the sensor connector. Verify reference supply and ground to the sensor and compare to expected values from factory data.
Measure sensor resistance at ambient temperature (engine off). Compare resistance to manufacturer specification or verify that resistance changes when gently warming/cooling the sensor (heat gun or ice pack) to confirm thermistor behavior.
Perform continuity check of wiring from sensor connector to seat module; check for shorts to ground or battery.
Wiggle harness/connectors while monitoring live data to find intermittent faults.
If wiring and connectors are good but sensor values are out of spec, replace the left rear seat temperature sensor and retest.
If new sensor does not correct the fault, inspect/replace the seat control/comfort module or investigate CAN/LIN communication issues per factory procedures.
Clear codes and perform a test drive or soak test to confirm repair. Document measurements before and after repair.

Likely causes

Connector at left rear seat sensor is loose or corroded
Broken or pinched wiring in seat harness (open/short to ground or supply)
Failed thermistor-type temperature sensor in the left rear seat
Faulty seat module or poor ground

Fault status

⚠️ Status

Left rear seat temperature sensor circuit fault detected (B1229). Service required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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B1229 — Left rear seat temperature sensor