Code
B1255
ALFA ROMEO
B — Body
External air temperature sensor open circuit
Views:
UK: 2
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Broken or chafed wiring in sensor harness
- Disconnected, corroded or damaged connector at the sensor
- Failed ambient/external air temperature sensor (open internally)
- Water ingress or corrosion at the sensor/connector
- Poor ground or reference circuit problem at the control module
- Faulty body/comfort control module or connector pins
Symptoms
- Ambient/external temperature display missing or shows incorrect value
- Automatic HVAC functions (auto climate, recirc logic) behaving incorrectly
- Heater/ventilation climate scheduling or sensor-dependent features disabled or defaulted
- Diagnostic trouble code B1255 stored and possibly warning message in dashboard
What to check
- Scan for stored codes and freeze-frame data; note any related climate/body codes
- Monitor ambient external temperature live data with a diagnostic tool while changing ambient conditions (hand near sensor)
- Visually inspect sensor (usually in front bumper/behind grille), harness and connector for corrosion, damage or water ingress
- Backprobe connector and measure continuity between sensor and control module
- Measure sensor resistance at ambient temperature and compare to specification (consult factory data)
- Check for proper reference voltage and ground at the sensor connector
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature increases)
- Typical signal behavior: resistance changes with ambient temperature; expected resistance varies by design (typical order of magnitude 1–100 kΩ at ordinary temperatures)
- If supplied as a voltage, expect a varying voltage within the module’s reference range (commonly ~0.5–4.5 V depending on design)
- Open-circuit symptom: infinite/high resistance (OL) or no measurable voltage from sensor
Diagnostic algorithm
- Connect a scan tool, read/record B1255 and any related codes; view live ambient temperature data.
- Visually inspect sensor location, connector and harness for water, corrosion, physical damage or aftermarket clips/repairs.
- With ignition ON, backprobe the sensor connector: verify reference voltage (if applicable) and ground. Record values.
- Remove sensor and measure resistance at ambient air temperature. Compare to manufacturer specification or expected thermistor behavior (resistance should change reasonably with temperature).
- If resistance is open (infinite), inspect wiring continuity from sensor connector to control module; repair any open circuits.
- Perform continuity and resistance checks on the harness including connector pins; repair or replace damaged wiring or connectors.
- If wiring and connector are good but sensor out of spec, replace sensor and retest. If replacement doesn’t clear code, check module connector and harness to body control module for open/shorts.
- After repairs, clear codes, verify live data shows plausible ambient temperature and perform a short drive or ambient change test to confirm the fault does not return.
Likely causes
- Damaged connector at sensor or wiring near front bumper
- Open sensor element (internal fault) from water damage
- Wire chafing/rodent damage causing open circuit
- Corroded connector pins causing intermittent open
Fault status
Status
External ambient air temperature sensor circuit open: control module detected no valid sensor signal or an open circuit and stored B1255.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
B1255
FIAT
B — Body
External air temperature sensor open circuit
Views:
UK: 3
EN: 5
RU: 3
AI status
Completed
Completed
100%
Causes
- Broken or chafed wiring in sensor harness
- Disconnected, corroded or damaged connector at the sensor
- Failed ambient/external air temperature sensor (open internally)
- Water ingress or corrosion at the sensor/connector
- Poor ground or reference circuit problem at the control module
- Faulty body/comfort control module or connector pins
Symptoms
- Ambient/external temperature display missing or shows incorrect value
- Automatic HVAC functions (auto climate, recirc logic) behaving incorrectly
- Heater/ventilation climate scheduling or sensor-dependent features disabled or defaulted
- Diagnostic trouble code B1255 stored and possibly warning message in dashboard
What to check
- Scan for stored codes and freeze-frame data; note any related climate/body codes
- Monitor ambient external temperature live data with a diagnostic tool while changing ambient conditions (hand near sensor)
- Visually inspect sensor (usually in front bumper/behind grille), harness and connector for corrosion, damage or water ingress
- Backprobe connector and measure continuity between sensor and control module
- Measure sensor resistance at ambient temperature and compare to specification (consult factory data)
- Check for proper reference voltage and ground at the sensor connector
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature increases)
- Typical signal behavior: resistance changes with ambient temperature; expected resistance varies by design (typical order of magnitude 1–100 kΩ at ordinary temperatures)
- If supplied as a voltage, expect a varying voltage within the module’s reference range (commonly ~0.5–4.5 V depending on design)
- Open-circuit symptom: infinite/high resistance (OL) or no measurable voltage from sensor
Diagnostic algorithm
- Connect a scan tool, read/record B1255 and any related codes; view live ambient temperature data.
- Visually inspect sensor location, connector and harness for water, corrosion, physical damage or aftermarket clips/repairs.
- With ignition ON, backprobe the sensor connector: verify reference voltage (if applicable) and ground. Record values.
- Remove sensor and measure resistance at ambient air temperature. Compare to manufacturer specification or expected thermistor behavior (resistance should change reasonably with temperature).
- If resistance is open (infinite), inspect wiring continuity from sensor connector to control module; repair any open circuits.
- Perform continuity and resistance checks on the harness including connector pins; repair or replace damaged wiring or connectors.
- If wiring and connector are good but sensor out of spec, replace sensor and retest. If replacement doesn’t clear code, check module connector and harness to body control module for open/shorts.
- After repairs, clear codes, verify live data shows plausible ambient temperature and perform a short drive or ambient change test to confirm the fault does not return.
Likely causes
- Damaged connector at sensor or wiring near front bumper
- Open sensor element (internal fault) from water damage
- Wire chafing/rodent damage causing open circuit
- Corroded connector pins causing intermittent open
Fault status
Status
External ambient air temperature sensor circuit open: control module detected no valid sensor signal or an open circuit and stored B1255.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
B1255
LAND ROVER
B — Body
Sensor ambient temperature in the car - circuit open
Views:
UK: 4
EN: 7
RU: 6
AI status
Completed
Completed
100%
Causes
- Broken or chafed wiring in sensor harness
- Disconnected, corroded or damaged connector at the sensor
- Failed ambient/external air temperature sensor (open internally)
- Water ingress or corrosion at the sensor/connector
- Poor ground or reference circuit problem at the control module
- Faulty body/comfort control module or connector pins
Symptoms
- Ambient/external temperature display missing or shows incorrect value
- Automatic HVAC functions (auto climate, recirc logic) behaving incorrectly
- Heater/ventilation climate scheduling or sensor-dependent features disabled or defaulted
- Diagnostic trouble code B1255 stored and possibly warning message in dashboard
What to check
- Scan for stored codes and freeze-frame data; note any related climate/body codes
- Monitor ambient external temperature live data with a diagnostic tool while changing ambient conditions (hand near sensor)
- Visually inspect sensor (usually in front bumper/behind grille), harness and connector for corrosion, damage or water ingress
- Backprobe connector and measure continuity between sensor and control module
- Measure sensor resistance at ambient temperature and compare to specification (consult factory data)
- Check for proper reference voltage and ground at the sensor connector
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature increases)
- Typical signal behavior: resistance changes with ambient temperature; expected resistance varies by design (typical order of magnitude 1–100 kΩ at ordinary temperatures)
- If supplied as a voltage, expect a varying voltage within the module’s reference range (commonly ~0.5–4.5 V depending on design)
- Open-circuit symptom: infinite/high resistance (OL) or no measurable voltage from sensor
Diagnostic algorithm
- Connect a scan tool, read/record B1255 and any related codes; view live ambient temperature data.
- Visually inspect sensor location, connector and harness for water, corrosion, physical damage or aftermarket clips/repairs.
- With ignition ON, backprobe the sensor connector: verify reference voltage (if applicable) and ground. Record values.
- Remove sensor and measure resistance at ambient air temperature. Compare to manufacturer specification or expected thermistor behavior (resistance should change reasonably with temperature).
- If resistance is open (infinite), inspect wiring continuity from sensor connector to control module; repair any open circuits.
- Perform continuity and resistance checks on the harness including connector pins; repair or replace damaged wiring or connectors.
- If wiring and connector are good but sensor out of spec, replace sensor and retest. If replacement doesn’t clear code, check module connector and harness to body control module for open/shorts.
- After repairs, clear codes, verify live data shows plausible ambient temperature and perform a short drive or ambient change test to confirm the fault does not return.
Likely causes
- Damaged connector at sensor or wiring near front bumper
- Open sensor element (internal fault) from water damage
- Wire chafing/rodent damage causing open circuit
- Corroded connector pins causing intermittent open
Fault status
Status
External ambient air temperature sensor circuit open: control module detected no valid sensor signal or an open circuit and stored B1255.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Code
B1255
Other
B — Body
Air Temperature External Sensor Circuit Open
Views:
UK: 14
EN: 29
RU: 18
AI status
Completed
Completed
100%
Causes
- Broken or chafed wiring in sensor harness
- Disconnected, corroded or damaged connector at the sensor
- Failed ambient/external air temperature sensor (open internally)
- Water ingress or corrosion at the sensor/connector
- Poor ground or reference circuit problem at the control module
- Faulty body/comfort control module or connector pins
Symptoms
- Ambient/external temperature display missing or shows incorrect value
- Automatic HVAC functions (auto climate, recirc logic) behaving incorrectly
- Heater/ventilation climate scheduling or sensor-dependent features disabled or defaulted
- Diagnostic trouble code B1255 stored and possibly warning message in dashboard
What to check
- Scan for stored codes and freeze-frame data; note any related climate/body codes
- Monitor ambient external temperature live data with a diagnostic tool while changing ambient conditions (hand near sensor)
- Visually inspect sensor (usually in front bumper/behind grille), harness and connector for corrosion, damage or water ingress
- Backprobe connector and measure continuity between sensor and control module
- Measure sensor resistance at ambient temperature and compare to specification (consult factory data)
- Check for proper reference voltage and ground at the sensor connector
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature increases)
- Typical signal behavior: resistance changes with ambient temperature; expected resistance varies by design (typical order of magnitude 1–100 kΩ at ordinary temperatures)
- If supplied as a voltage, expect a varying voltage within the module’s reference range (commonly ~0.5–4.5 V depending on design)
- Open-circuit symptom: infinite/high resistance (OL) or no measurable voltage from sensor
Diagnostic algorithm
- Connect a scan tool, read/record B1255 and any related codes; view live ambient temperature data.
- Visually inspect sensor location, connector and harness for water, corrosion, physical damage or aftermarket clips/repairs.
- With ignition ON, backprobe the sensor connector: verify reference voltage (if applicable) and ground. Record values.
- Remove sensor and measure resistance at ambient air temperature. Compare to manufacturer specification or expected thermistor behavior (resistance should change reasonably with temperature).
- If resistance is open (infinite), inspect wiring continuity from sensor connector to control module; repair any open circuits.
- Perform continuity and resistance checks on the harness including connector pins; repair or replace damaged wiring or connectors.
- If wiring and connector are good but sensor out of spec, replace sensor and retest. If replacement doesn’t clear code, check module connector and harness to body control module for open/shorts.
- After repairs, clear codes, verify live data shows plausible ambient temperature and perform a short drive or ambient change test to confirm the fault does not return.
Likely causes
- Damaged connector at sensor or wiring near front bumper
- Open sensor element (internal fault) from water damage
- Wire chafing/rodent damage causing open circuit
- Corroded connector pins causing intermittent open
Fault status
Status
External ambient air temperature sensor circuit open: control module detected no valid sensor signal or an open circuit and stored B1255.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email