P0168
Fuel Temperature Too High
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P0168 means the powertrain control module has detected that fuel temperature has exceeded its acceptable operating range. Modern fuel-injected vehicles rely on precise fuel metering, and excessively hot fuel can cause vapor lock, poor atomization, and inaccurate fuel delivery because hot fuel is less dense than cool fuel.
When fuel gets too hot, it can start to vaporize in the fuel lines and fuel rail before reaching the injectors. This creates air pockets in the fuel system that lead to hard starting, rough running, stalling, and reduced power. The PCM may activate a reduced-power or limp mode to protect the engine. This code is more common in hot climates, during extended idling, and in vehicles that have lost fuel line heat shielding.
Diagnosis should start with checking the fuel temperature sensor and its wiring, as a faulty sensor is the most common cause. If the sensor checks out, inspect the fuel return line for kinks or restrictions that prevent hot fuel from circulating back to the tank. Also check for missing or damaged heat shields around fuel lines. This is rated as moderate severity — while the vehicle is still drivable, prolonged operation with excessively hot fuel can cause fuel pump damage and poor engine performance.
Severity
Symptoms
- •Check Engine Light is on
- •Reduced engine power or limp mode activation
- •Hard starting especially in hot weather
- •Engine stalling or rough running
- •Increased vapor lock symptoms
- •Fuel smell near the engine bay
Likely Causes
The fuel temperature sensor is reading incorrectly and reporting a higher temperature than the fuel actually is, causing the PCM to store this code even though fuel temperature may be normal.
Insufficient insulation or shielding of fuel lines and the fuel rail allows engine heat to raise fuel temperature above acceptable levels, particularly during prolonged idling or hot weather.
A kinked, clogged, or restricted fuel return line prevents hot fuel from circulating back to the tank for cooling, causing fuel temperature to build up in the engine bay.
A fuel pump that is working harder than normal due to wear or electrical issues generates excessive heat, raising the temperature of the fuel passing through it.
Shorted or damaged wiring to the fuel temperature sensor creates incorrect voltage readings that the PCM interprets as excessively high fuel temperature.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the fuel temperature sensor
- Inspect and repair fuel return lines for restrictions
- Add or replace heat shielding on fuel lines and fuel rail
- Repair damaged wiring in the fuel temperature sensor circuit
- Replace failing fuel pump if running excessively hot