Code
B1226
ALFA ROMEO
B — Body
Fuel temperature sensor 2 out of range / performance
Views:
UK: 6
EN: 7
RU: 9
AI status
Completed
Completed
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Causes
- Faulty fuel temperature sensor (NTC thermistor) 2
- Open, short or high-resistance wiring in sensor 2 circuit
- Corroded or loose connector at the sensor or ECU
- Water or contamination in the fuel affecting the sensor
- Poor ground or power supply issue for the sensor circuit
- Intermittent connection due to vibration or damaged harness
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Incorrect fuel temperature values reported in scan tool live data
- Poor cold/hot start behavior or drivability issues
- Possible increased emissions or reduced fuel economy
- Stored related fuel or trim adaptive faults (running rich/lean)
What to check
- Read freeze-frame and scan-tool live data for Fuel Temp Sensor 1 and 2
- Confirm whether fault is current, intermittent or historical
- Visually inspect sensor 2 connector and wiring for damage, corrosion or fuel intrusion
- Measure sensor 2 harness voltage and ground with key ON (engine OFF)
- Measure sensor resistance at the connector and compare to OEM spec
- Compare sensor 2 reading to sensor 1 and to ambient/fuel temperature
Signal parameters
- Sensor type: typically an NTC thermistor (resistance decreases as temperature rises)
- Typical signal voltage range: ~0.1–4.9 V (varies by vehicle—consult OEM spec)
- Typical resistance behavior: high resistance at low temps, lower resistance at high temps (consult specific sensor table)
- Expected diagnostic behavior: smooth, continuous temperature change when warmed/cooled; sudden jumps or stuck values indicate fault
- Compare Sensor 2 values to Sensor 1 — large discrepancy suggests sensor/circuit fault
Diagnostic algorithm
- Read and record DTC(s) and freeze-frame data. Clear codes and attempt to reproduce the fault while monitoring live fuel temperature sensors.
- Visually inspect sensor 2 and harness for obvious damage, corrosion, fuel wetting, or loose connector. Repair any visible issues.
- With ignition ON (engine OFF) back-probe the sensor connector. Verify reference voltage and ground presence per OEM procedure.
- Measure sensor resistance at the connector. If possible, compare resistance at known temperatures (room temp and warmed) or compare to sensor 1. Replace if out of spec.
- Perform a controlled functional test: warm the sensor (warm water or heat gun at safe distance) and observe a smooth change in voltage/resistance. Do not use open flame or direct high heat.
- Check continuity between sensor harness and ECU connector—look for shorts to ground or power and high resistance connections.
- If wiring and connector check good and new/replacement sensor still fails, consider ECU input fault. Confirm with known-good ECU or consult dealer-level diagnostics.
- After repair or replacement, clear codes and road-test to ensure the DTC does not return. If required, follow any manufacturer-specific coding/initialization procedures.
Likely causes
- Failed/ageing sensor 2
- Damaged wiring or connector for sensor 2
- Corrosion/contamination at connector
- Fuel contamination (water/debris) affecting reading
- ECU input fault (after wiring/sensor checks)
Fault status
Status
Fuel temperature sensor 2 circuit – signal out of range or performance fault detected by control module.
Repair difficulty: Medium
Diagnostic time: 0.5-3.0 hours
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