P0168Generic code

P0168 Code: Fuel Temperature Too High

The P0168 code means the fuel temperature is above the allowed limit. It shows up mostly on diesels, because of a clogged fuel cooler, a low fuel level in the tank or a sensor that reads wrong.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$0 to $1,500
Difficulty
Medium
System
Fuel Injection
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

On this page

What the P0168 code means

On diesels, the fuel left over from the pump and the injectors returns hot to the tank. If the fuel gets too hot, it loses density and lubricating ability, and the high-pressure pump suffers. The computer watches the temperature and, above the limit (often 80 to 100 °C, or 176 to 212 °F), it stores the P0168 code and limits power.

It can also show up on flex fuel vehicles. Before you replace the sensor, check whether the fuel is really hot.

P0168 code symptoms

  • Loss of power or limp mode.
  • Harder to start when hot.
  • Check engine light on.
  • It often shows up in summer, with the tank nearly empty.

Likely causes of the P0168 code

  1. Very low fuel level. There is less fuel to soak up the heat of the return flow.
  2. Fuel cooler clogged with dirt on the outside.
  3. Injectors with excess return flow, which heat up more fuel.
  4. Fuel temperature sensor out of calibration.
  5. Cooler bypass valve stuck.

How to diagnose the P0168 code step by step

  1. Compare the fuel temperature with the air temperature after the vehicle has sat for several hours: they should match.
  2. Measure the return line with an infrared thermometer to see whether the fuel is really that hot.
  3. Inspect the fuel cooler under the vehicle or in front of the radiator.
  4. Run the injector return test to look for excess return flow.
  5. Measure the sensor resistance and compare it with the chart.

How to fix the P0168 code

  • Keep the tank above a quarter full in summer.
  • Clean the fuel cooler.
  • Replace injectors with excess return flow.
  • Replace the sensor if it reads wrong.

Technical reference data

  • Normal fuel temperature on diesels: 30 to 70 °C (86 to 158 °F).
  • Typical code limit: 80 to 100 °C (176 to 212 °F).
  • Approximate values only.

Brand-specific notes

Common on diesels in hot climates.

P0168 on Mercedes-Benz

Seen often on Mercedes-Benz diesels in hot climates.

P0168 on Volkswagen

Seen often on Volkswagen diesels in hot climates.

P0168 on Ford

Seen often on Ford diesels in hot climates.

Frequently asked questions about P0168

Can I drive with a P0168 code?
With caution. A P0168 code is a reason to fill the tank and avoid heavy loads until you have it checked.
Why does it show up with the tank nearly empty?
Because the hot fuel coming back from the return line heats the small amount left in the tank much faster.
Can it damage the high-pressure pump?
Yes. Very hot fuel lubricates worse, and that wears the pump.
How much does it cost to fix P0168?
Anywhere from $0 (just filling the tank) to $1,500 if the injectors are damaged.
What is the most common cause of P0168?
A very low fuel level in the tank, especially in summer. A clogged fuel cooler and injectors with excess return flow come next.

Related codes

Questions about the P0168 code

There are no questions about this code yet. Tell us about your case: vehicle, symptoms and what you have already checked.