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 petrol 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.
Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
Symptoms
- Check engine light on
- Usually no change in driving
Most likely causes
- Sensor drifting (characteristic shifted)
- Comparison sensor wrong (charge air, coolant, intake air)
- Contact resistance in the connector
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0186 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 86: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0186?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P0186?
The most common causes are: sensor drifting (characteristic shifted); comparison sensor wrong (charge air, coolant, intake air); contact resistance in the connector.
Related codes
- P0185Fuel Temperature Sensor B Circuit
- P0187Fuel Temperature Sensor B Circuit Low
- P0188Fuel Temperature Sensor B Circuit High
- P0189Fuel Temperature Sensor B Circuit Intermittent
- P0181Fuel Temperature Sensor A Circuit Range/Performance
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.