OBD-II Generic Error Code P0186: Fuel Temperature Sensor B Low - How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
P0187
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code P0186 indicates that the Engine Control Module (ECM) has detected a low voltage signal from the fuel temperature sensor B. This typically means the sensor or its circuit is malfunctioning. Ignoring this code can lead to poor fuel economy and drivability issues.
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Tools You'll Need

How to Fix Error Code P0187

  1. Safety First & Preparation

    Always disconnect the battery before working on electrical components.

  2. Locate Fuel Temperature Sensor B

  3. Inspect Wiring and Connector

    Do not use sharp objects to clean pins; use a plastic brush or compressed air.

  4. Test Sensor Resistance

    Avoid touching the sensor immediately after engine operation to prevent burns.

  5. Test Voltage at Connector

    Be careful not to short pins together while probing.

  6. Replace Sensor if Needed

    Use a new O-ring or gasket if provided. Do not over-tighten.

  7. Clear the Code and Test

    Ensure the vehicle is in park or neutral with the parking brake engaged.

Parts You May Need

Fuel Temperature Sensor B
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Connector Pigtail (if damaged)
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Fuel Temperature Sensor B
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Connector Pigtail (if damaged)
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Fuel Temperature Sensor B
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Connector Pigtail (if damaged)
Check Price on Amazon
Fuel Temperature Sensor B
Check Price on Amazon
Connector Pigtail (if damaged)
Check Price on Amazon
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When to Call a Professional

If you have limited experience with automotive electrical systems, or if testing reveals an ECM issue (no voltage at all), consult a professional mechanic. Also, if the code returns after sensor replacement, further diagnostics (e.g., wiring harness integrity, ECM check) may require specialized tools.

Frequently Asked Questions

What does OBD-II error code P0186 mean?
P0186 indicates the fuel temperature sensor B circuit has low voltage/input. This means the sensor reading is below the normal range, often due to a faulty sensor, wiring issue, or ECM problem.
Can I drive with a P0186 code?
Yes, but it may cause poor fuel economy, rough idle, or hard starting. It's best to diagnose and fix it promptly to avoid further issues.
How much does it cost to fix P0186?
The fuel temperature sensor typically costs $20-$70. If you DIY, you save labor. A mechanic may charge $100-$200 for diagnosis and replacement.
Where is the fuel temperature sensor B located?
It is usually mounted on the fuel rail or fuel line near the engine. Check your vehicle's service manual for the exact location.
Will disconnecting the battery clear P0186?
It may temporarily clear the code, but it will return if the underlying issue isn't fixed. Use an OBD2 scanner to clear codes after repair.

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