P0168 is not a sensor fault but an operating condition, almost only on diesels: the fuel temperature sensor reports fuel hotter than a protective limit. The fuel heats up through the return flow from the high-pressure pump and injectors, especially with little fuel in the tank, at idle after full load, in hot weather or with a failed fuel cooler; one manufacturer patent names about 80 °C as the upper limit to protect seals, against a normal range of roughly 5–60 °C. On Saab's Bosch EDC16 diesels the code means an engine protection function is active and injection quantity is reduced. No manufacturer threshold was found, and GM's and Ford's diesel summaries do not use P0168. Whether the warning light comes on depends on the manufacturer.
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
- Loss of power, limp mode (reduced injection quantity)
- Warning light depending on manufacturer
- Occurs in heat, at full load, with little fuel in the tank
Most likely causes
- Fuel cooler (air or water cooler in the return) dirty or faulty, coolant circuit disturbed
- Very little fuel in the tank at high load or heat
- Excessive return flow from worn high-pressure pump or injectors, or faulty overflow valve
- Fuel temperature sensor drifting and reading too high
- Engine overheating or overload (trailer, gradient)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
What each character of P0168 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 68: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0168?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P0168?
The most common causes are: fuel cooler (air or water cooler in the return) dirty or faulty, coolant circuit disturbed; very little fuel in the tank at high load or heat; excessive return flow from worn high-pressure pump or injectors, or faulty overflow valve.
Related codes
- P0181Fuel Temperature Sensor A Circuit Range/Performance
- P0182Fuel Temperature Sensor A Circuit Low
- P0183Fuel Temperature Sensor A Circuit High
- P0217Engine Coolant Over Temperature Condition
- P0087Fuel Rail/System Pressure - Too Low
- P008FEngine Coolant Temperature/Fuel Temperature Correlation
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.