2018 RAM 2500 Cummins P0168 - Fuel Temperature Too High

Question

My truck is throwing a P0168 code and entering a mild limp mode after towing my fifth wheel for about thirty minutes. The overhead console shows the fuel temperature climbing steady until the CEL pops. I am worried about damaging the CP4 pump if the fuel actually is getting that hot.

Jake Morrison · Accepted Answer

The issue ended up being the Fuel Temperature Sensor integrated into the low-pressure supply line. I verified with a scan tool that the sensor was reading 210F while the actual fuel at the service port was only 115F. I replaced the sensor assembly (Part #68199395AB), which cost about $85 and took 20 minutes to swap out. Cleared codes and the truck has been running cool even under heavy load.

Chris Donovan · Answer

Inspect the fuel heater element in the fuel filter housing. Sometimes the relay sticks on, which causes the heater to run constantly even when the ambient temperature is high, leading to a P0168.

Dave Kowalski · Answer

Check your fuel return rates. If an injector is stuck partially open or returning too much fuel to the rail, it carries a lot of combustion heat back to the tank, eventually heat-soaking the system.

Kevin Tran · Answer

You should use an infrared thermometer to verify the actual temperature at the fuel cooler and the return line. If the sensor says 180 degrees but the line feels lukewarm, you likely just have a skewed thermistor in the sensor.

2018 RAM 2500 Cummins P0168 - Fuel Temperature Too High

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