Fueling mode changing while cruising

[HighMiles]

While driving along the fuel mode flips to the high rpm underload full fuel shot mode (load diesel rattle) at the same time temp. guage also drops or flutters. I beleive the mode changes first then the guage moves.

This is an 01' with 235k and has had two new fuel pumps and one set of injectors. After it came back from the last fuel pump it had started running rough and the Service Engine light came on. Found that the boot of the temp. sending unit was broken and the wire came off put it back on and was fine. 30K later this problem started and I replaced the temp. sending unit and it worked, or seemed too for a couple of months but now it is acting up again. No Service Engine light yet. I assume not likely a bad temp. sending unit since the mode changes sometimes before the guage moves.

Looking for ideas before I park it in the shop $$$$$$. Its always good to be informed before you see the those people.

Thanks

[DmaxMaverick]

That's a tough one. Sounds like your temp sender is losing contact, and giving the PCM a false indication of tempurature. If the PCM thinks the ECT -40

[HighMiles]

No I didn't check the codes the first time when the SES light was on since it was a wire that came off the Temp. sending unit and it cleared after it was connected. The flipping in and out has not caused the SES light to come on yet.

Cold (65-70 degrees F) ohms of the current temp. sending unit this AM was 2.41K if that sounds right.

[HighMiles]

I think the problem is solved. Thanks to the other posts I was able to check the ohms of the sending unit and found it was fine. The original sending unit was damaged by the dealer that replaced the fuel pumps or injectors. It was not obvious but the wire harness end must have been damaed too. I replaced the end and it seemed to solve the problem.

Thanks to all who post here.