P0186 code meaning
Fuel Temperature Sensor B Circuit Range/Performance
Powertrain system Generic code P01xx codes Check engine light
What P0186 means
Fuel temperature sensor B is an NTC thermistor: the hotter the fuel, the lower its resistance and signal voltage. On diesels it sits in the injection pump, rail or return line; on Ford gasoline direct-injection engines it is built into the rail pressure sensor, and GM uses digital rail temperature sensors on its direct-injection engines. Sensor B is the second measuring point, for example GM's 6.6 litre diesel sensor 2 or a second rail. P0186 is the plausibility check of sensor B, the counterpart of P0181 – presumably a comparison with a reference sensor after a long standstill, as GM documents for sensor A (8 h, 20 °C). No manufacturer using P0186 was found; the description rests on CARB and the sensor A strategy.
P0186 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0186
- Check engine light on
- Usually no change in driving
Common causes of P0186
- Most likelySensor drifting (characteristic shifted)
- PossibleComparison sensor wrong (charge air, coolant, intake air)
- PossibleContact resistance in the connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel temperature sensor bSensor wiring
What each part of P0186 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 86 | The exact fault in that area. |
What to do next
- Note P0186 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0186
What does P0186 mean?
P0186 means "Fuel Temperature Sensor B Circuit Range/Performance". Fuel temperature sensor B is an NTC thermistor: the hotter the fuel, the lower its resistance and signal voltage. It is a generic code, so it means the same on every make.
Is it safe to drive with P0186?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0186 fail an emissions test?
Yes, it can. P0186 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0186 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will P0186 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.