Code
B1387
ALFA ROMEO
B — Body
Oil temperature sensor open or short to positive
Views:
UK: 1
EN: 6
RU: 6
AI status
Completed
Completed
100%
Causes
- Open circuit in oil temperature sensor wiring (broken wire, poor connector contact)
- Short to battery positive on the sensor signal or supply wire
- Corroded or contaminated sensor connector
- Failed oil temperature sensor (internal open or short)
- Water ingress or damaged insulation in harness
- Faulty control module or internal input circuit failure (less common)
Symptoms
- Oil temperature gauge reading erratic, pegged, or unavailable
- Instrument cluster or MIL may illuminate depending on system
- Oil-related warnings or service messages on dash
- Possible altered engine management behavior if oil temperature is used by ECU
- No obvious oil leak or mechanical oil temperature problem
What to check
- Read stored and pending DTCs and freeze-frame data with a scan tool
- Visual inspection of sensor, connector, and wiring for damage, corrosion, or water
- Backprobe sensor signal and reference pins with ignition ON (engine OFF) and observe voltage
- Measure sensor resistance at ambient and with controlled heating (compare with spec)
- Check for continuity to the control module and for shorts to battery positive
- Wiggle harness and connector while monitoring signal to reproduce fault
Signal parameters
- Typical sensor type: thermistor (variable resistance) working as part of a divider — consult factory spec
- Typical resistance example (informative only): several hundred to several thousand ohms depending on temperature and design
- Typical signal voltage at ECU: varies between ~0.5 V and ~4.5 V across operating range (design-dependent)
- Reference supply commonly 5 V (or vehicle reference); open circuit or short-to-positive will show out-of-range voltage
- Always verify exact resistance/voltage specifications from the Alfa Romeo service manual for the specific model/year
Diagnostic algorithm
- Retrieve all codes and freeze-frame data; note any related codes (powertrain or body).
- Visually inspect oil temperature sensor connector and wiring for corrosion, loose pins, or damage.
- With ignition ON (engine OFF), backprobe the sensor connector: verify reference voltage and ground presence per factory values.
- Measure the signal voltage at the ECU input with key ON while comparing to expected values; an open or short-to-positive will typically read out-of-range (very high or fixed voltage).
- Check continuity of the signal wire between sensor and ECU; check for short to battery positive (measure resistance between signal wire and battery + with ignition OFF).
- Remove sensor and measure its resistance at known ambient temperature and while warming (hot water) to confirm thermistor behavior versus specification.
- If wiring and connector are good but sensor is out of spec, replace the oil temperature sensor and retest.
- If sensor and harness test good but fault persists, inspect/replace connector or repair wiring. If still unresolved, consider module input fault and consult dealer-level diagnostics.
- After any repair, clear codes and perform a drive cycle or run the component self-test to verify the repair.
Likely causes
- Damaged/loose connector at the oil temperature sensor
- Broken wire in harness between sensor and ECU/body control module
- Sensor element failed open or internally shorted to supply
- Aftermarket work or repairs that disturbed the harness
Fault status
Status
Oil temperature sensor circuit — open or short to positive detected. Service required: inspect sensor and wiring.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1387
FIAT
B — Body
Oil temperature sensor open or short to positive
Views:
UK: 2
EN: 2
RU: 6
AI status
Completed
Completed
100%
Causes
- Open circuit in oil temperature sensor wiring (broken wire, poor connector contact)
- Short to battery positive on the sensor signal or supply wire
- Corroded or contaminated sensor connector
- Failed oil temperature sensor (internal open or short)
- Water ingress or damaged insulation in harness
- Faulty control module or internal input circuit failure (less common)
Symptoms
- Oil temperature gauge reading erratic, pegged, or unavailable
- Instrument cluster or MIL may illuminate depending on system
- Oil-related warnings or service messages on dash
- Possible altered engine management behavior if oil temperature is used by ECU
- No obvious oil leak or mechanical oil temperature problem
What to check
- Read stored and pending DTCs and freeze-frame data with a scan tool
- Visual inspection of sensor, connector, and wiring for damage, corrosion, or water
- Backprobe sensor signal and reference pins with ignition ON (engine OFF) and observe voltage
- Measure sensor resistance at ambient and with controlled heating (compare with spec)
- Check for continuity to the control module and for shorts to battery positive
- Wiggle harness and connector while monitoring signal to reproduce fault
Signal parameters
- Typical sensor type: thermistor (variable resistance) working as part of a divider — consult factory spec
- Typical resistance example (informative only): several hundred to several thousand ohms depending on temperature and design
- Typical signal voltage at ECU: varies between ~0.5 V and ~4.5 V across operating range (design-dependent)
- Reference supply commonly 5 V (or vehicle reference); open circuit or short-to-positive will show out-of-range voltage
- Always verify exact resistance/voltage specifications from the Alfa Romeo service manual for the specific model/year
Diagnostic algorithm
- Retrieve all codes and freeze-frame data; note any related codes (powertrain or body).
- Visually inspect oil temperature sensor connector and wiring for corrosion, loose pins, or damage.
- With ignition ON (engine OFF), backprobe the sensor connector: verify reference voltage and ground presence per factory values.
- Measure the signal voltage at the ECU input with key ON while comparing to expected values; an open or short-to-positive will typically read out-of-range (very high or fixed voltage).
- Check continuity of the signal wire between sensor and ECU; check for short to battery positive (measure resistance between signal wire and battery + with ignition OFF).
- Remove sensor and measure its resistance at known ambient temperature and while warming (hot water) to confirm thermistor behavior versus specification.
- If wiring and connector are good but sensor is out of spec, replace the oil temperature sensor and retest.
- If sensor and harness test good but fault persists, inspect/replace connector or repair wiring. If still unresolved, consider module input fault and consult dealer-level diagnostics.
- After any repair, clear codes and perform a drive cycle or run the component self-test to verify the repair.
Likely causes
- Damaged/loose connector at the oil temperature sensor
- Broken wire in harness between sensor and ECU/body control module
- Sensor element failed open or internally shorted to supply
- Aftermarket work or repairs that disturbed the harness
Fault status
Status
Oil temperature sensor circuit — open or short to positive detected. Service required: inspect sensor and wiring.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
B1387
Other
B — Body
Oil Temperature Sensor Circuit Open
Views:
UK: 11
EN: 19
RU: 22
AI status
Completed
Completed
100%
Causes
- Open circuit in oil temperature sensor wiring (broken wire, poor connector contact)
- Short to battery positive on the sensor signal or supply wire
- Corroded or contaminated sensor connector
- Failed oil temperature sensor (internal open or short)
- Water ingress or damaged insulation in harness
- Faulty control module or internal input circuit failure (less common)
Symptoms
- Oil temperature gauge reading erratic, pegged, or unavailable
- Instrument cluster or MIL may illuminate depending on system
- Oil-related warnings or service messages on dash
- Possible altered engine management behavior if oil temperature is used by ECU
- No obvious oil leak or mechanical oil temperature problem
What to check
- Read stored and pending DTCs and freeze-frame data with a scan tool
- Visual inspection of sensor, connector, and wiring for damage, corrosion, or water
- Backprobe sensor signal and reference pins with ignition ON (engine OFF) and observe voltage
- Measure sensor resistance at ambient and with controlled heating (compare with spec)
- Check for continuity to the control module and for shorts to battery positive
- Wiggle harness and connector while monitoring signal to reproduce fault
Signal parameters
- Typical sensor type: thermistor (variable resistance) working as part of a divider — consult factory spec
- Typical resistance example (informative only): several hundred to several thousand ohms depending on temperature and design
- Typical signal voltage at ECU: varies between ~0.5 V and ~4.5 V across operating range (design-dependent)
- Reference supply commonly 5 V (or vehicle reference); open circuit or short-to-positive will show out-of-range voltage
- Always verify exact resistance/voltage specifications from the Alfa Romeo service manual for the specific model/year
Diagnostic algorithm
- Retrieve all codes and freeze-frame data; note any related codes (powertrain or body).
- Visually inspect oil temperature sensor connector and wiring for corrosion, loose pins, or damage.
- With ignition ON (engine OFF), backprobe the sensor connector: verify reference voltage and ground presence per factory values.
- Measure the signal voltage at the ECU input with key ON while comparing to expected values; an open or short-to-positive will typically read out-of-range (very high or fixed voltage).
- Check continuity of the signal wire between sensor and ECU; check for short to battery positive (measure resistance between signal wire and battery + with ignition OFF).
- Remove sensor and measure its resistance at known ambient temperature and while warming (hot water) to confirm thermistor behavior versus specification.
- If wiring and connector are good but sensor is out of spec, replace the oil temperature sensor and retest.
- If sensor and harness test good but fault persists, inspect/replace connector or repair wiring. If still unresolved, consider module input fault and consult dealer-level diagnostics.
- After any repair, clear codes and perform a drive cycle or run the component self-test to verify the repair.
Likely causes
- Damaged/loose connector at the oil temperature sensor
- Broken wire in harness between sensor and ECU/body control module
- Sensor element failed open or internally shorted to supply
- Aftermarket work or repairs that disturbed the harness
Fault status
Status
Oil temperature sensor circuit — open or short to positive detected. Service required: inspect sensor and wiring.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 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