Code
B1255
LAND ROVER
B — Body
Sensor ambient temperature in the car - circuit open
Views:
UK: 4
EN: 8
RU: 6
AI status
Completed
Completed
100%
Causes
- Open or broken wiring (connector to sensor)
- Corroded or loose connector terminals
- Failed ambient temperature sensor (open thermistor)
- Poor ground or reference supply to the sensor
- Faulty HVAC/BCM/IPC control module or internal connector fault
Symptoms
- Ambient/outside temperature reading absent, fixed at extreme value, or displaying '--'
- Climate control may not operate in expected automatic mode or may use incorrect logic
- Driver information display shows incorrect outside temperature
- Possible intermittent HVAC behavior tied to outside temperature
What to check
- Read and record freeze-frame and any additional stored codes with a scan tool
- Visually inspect sensor location (usually in front bumper/grille) and wiring for damage or corrosion
- Check connector for water ingress, bent pins, corrosion or looseness
- Backprobe sensor connector with ignition ON to verify reference voltage and ground presence
- Measure sensor resistance at harness side with sensor disconnected (compare to expected values)
- Continuity check from sensor connector to the control module connector
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature rises)
- Common nominal resistance: ~10 kΩ at 25°C (varies by manufacturer) — consult vehicle-specific data
- Typical signal behavior: variable resistance; module reads voltage across thermistor or ADC value
- Open-circuit indication: very high resistance (>>100 kΩ) or 'OL', or signal voltage pinned near supply or open value
- Expected voltage range (vehicle-specific): roughly 0.5–4.5 V depending on circuit and reference topology
Diagnostic algorithm
- Confirm code with a scan tool, note freeze-frame and any related HVAC or module codes.
- Perform a visual inspection of the sensor and wiring at the mounting location (look for damage, impact, water).
- Disconnect sensor connector and inspect pins for corrosion, bent or pushed-out terminals; repair or replace connector as needed.
- With ignition ON (engine off), backprobe the connector: verify reference voltage (if present) and good ground continuity to chassis ground and module ground.
- Measure the sensor resistance at the harness end with the sensor removed; compare to specification (expect NTC behavior). If open (infinite/high resistance), replace sensor.
- If sensor resistance is OK, check continuity and resistance between the harness connector and the HVAC/control module pins. Repair any opens or high-resistance sections.
- If wiring and sensor check good, test the control module inputs/outputs or swap with a known-good module/sensor if possible. Consult wiring diagrams and module pinouts.
- After repair or replacement, clear codes and verify repair by monitoring live ambient temp value and ensuring code does not return after test drive.
Likely causes
- Sensor disconnected or physically damaged (visible plug-out)
- Water ingress/corrosion at sensor connector (common on exterior sensors)
- Wire chafing or break in harness between sensor and control module
- Terminal pushed out of connector or bent pin
- Failed sensor element (open thermistor)
Fault status
Status
Ambient temperature sensor circuit open — open/high resistance detected in outside air temperature sensor circuit. HVAC/comfort control module has logged a fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
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