P0186: Fuel Temperature Sensor B Circuit Range/Performance
What to do
Usually driveable. Diagnose on a diesel rather than deferring.
What this code means
The second fuel temperature reading is implausible against the other sensors. Where sensors A and B are meant to sit at different points in the circuit, remember that a genuine difference between them is expected — this code means the difference has gone outside what the system can explain.
Likely causes
Start here
- Faulty fuel temperature sensor · moderate
Less common
- Blocked fuel return line · moderate
- Failed fuel cooler · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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