I am a first time poster, looking for some expert opinions. I have a small shop in my house that I do side work on friends/family vehicles. I replaced a rear main seal on an 05, and while I was at it the customer wanted me to update the fuel filter head, he had recently done a timing belt before bringing it to me. I got the new filter head on, bled the air once and the jeep started right up. It idled great and I had it running for about 5 min while I charged the A/C. I did notice that there was a check engine light on. I scanned the car and the code was P0168, fuel temperature sensor-high reading. The fuel temp sensor is brand new, it came on the new head, so where do I go from here? Is there a sanity check I can do to check the function of the fuel temp sensor?

Thanks in advance for any help.

I don't find that as a valid code in my KJ code list or the 06 FSM (05 FSM lacks the codes) but I do find a P0180 in the 06 FSM with the same description. Pull a copy of that FSM from Sir Sam's NOOB guide and see what the diagnostics say.

It's not impossible you got a bad new head unit. I assume you hooked up the new fuel temp power plug based on best match to wire size, colors don't match, and that the splice is well insulated.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Thanks for the quick reply, I have the 05 FSM on my home computer, so I'll double check that when I get home, but I'm sure that it was a fuel temp too high code. The old wires were 2 different sizes, and there were 2 sizes that came with the head, both of them larger than the original wires. I soldered and put heat shrink tubing and then put the 2 wires back in the convoluted tubing. Those wires are for the fuel heater plug though, why would a connection issue there show up as fuel temp too high? I have the old filter head, if I check the resistance at room temperature of the temp sensor on the old head, it should be fairly close to that of the new one right?

The 05 FSM won't help you at all as the online and hard copy versions have no diagnostic codes. In 05 the diagnostic manuals were separate publications which were rolled into the FSM in 06. That's why I said get the 06 manual. I do have "e" copies of the 05 diagnostic manuals and both the 05 Diesel diagnostic manual and the 06 FSM list P0180 as a fuel heater high/low reading and provide some guidance on how to test.

I'm by no means an electrical person but suspect so "leakage" between the 2 fuel heater wires could cause a high reading which is why I asked about the connections and speculated about a bad new fuel head.

Best bet is to run the referenced tests and see what they tell you which might or might not be helpful since I suspect those tests are based on the 1st gen fuel heater.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

My mistake, the code was P0183, Fuel Temperature sensor circuit A high input.

It would appear the new temp sensor either a) isn't connected or b) defective.

Check the wiring for continuity.. you could plug in the old sensor (leave it hanging) to check the wiring and see if the CEL goes away. You'll need to reset the code or wait for enough starts to clear automatically.

If the old sensor will fit the new head, move it.

If it's the sensor, and the old one doesn't fit, you can live without it while you get a replacement (warranty, etc). It will probably pick a safe value so that if the fuel gets too warm, the default value will protect the engine. This would translate into something less than max power but otherwise it should run fine and be more than good enough for the commute.

It's design is to cause the ECM to de-fuel to protect the high-pressure pump (CP3) when the fuel is too warm.

Mark

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2005 Liberty CRD
2004.5 Cummins 5.9L TD, F1s, NV5600 6-speed in a '93 GMC Suburban

The sensor is integral to the head, so no luck changing it, but I did remove the filter from the old head and plugged the old sensor into the vehicle and now the check engine light is cleared. This confirms that the new part has a defective sensor. This is the first time that I have ever got a new part that was bad. I assumed that the problem had to be something that I created, oh well, first time for everything. I will see if the place that he bought the head assembly from will warranty the part. In the mean time the old head will have to ride around in the engine compartment until the new one comes.