2018 Ram 2500 Cummins P0168 - Fuel Temperature Too High

Question

My truck is throwing a P0168 code and the instrument cluster is warning me about high fuel temps after driving for about 30 minutes. It seems to happen mostly on the highway when I am towing my camper. The truck feels like it is losing power or derating slightly once the code pops up.

Chris Donovan · Accepted Answer

Found the issue was a failing lift pump causing low supply pressure, which made the CP3 pump work harder and generate excess heat. However, the real culprit for the P0168 was a restricted fuel return cooler located on the frame rail (Part #68197868AA). Replaced the cooler assembly and the Fuel Temperature Sensor, then flushed the return lines. Total cost for parts was about $450 and temperatures are back to 110-120 degrees even when pulling 10k lbs.

Mike Reynolds · Answer

Check the fuel cooler bypass valve if your model has the frame-mounted cooler. If the thermostat in the bypass block fails, it won't route the fuel through the heat exchanger, leading to rapid heat soak under load.

dieselmike88 · Answer

Check the fuel return line for any kinks or restrictions. If the fuel can't return to the tank fast enough, it stays in the rail area longer and picks up a lot of heat from the cylinder head.

Lina Brooks · Answer

You might want to check the Fuel Temperature Sensor (FTS) resistance. Sometimes the sensor internal resistance drifts and reports a higher temperature than actual, even though the fuel is fine.

2018 Ram 2500 Cummins P0168 - Fuel Temperature Too High

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