Recent history on the truck..

New injectors about 3k miles ago, BRAND NEW, cummins, not rebuilds or remanufactured, Truck ran flawlessly for 3000 miles, hard towing and all so i thought all was ok..

four days ago, i started getting that lopey idle that most deushbag smokers want, and that regular folks hate. I thought nothing of it, but knew that the biggest possibilities were either air in the lines somewhere, or the stock 203K FCA was going out.. I threw the DTC codes.. same ones that i HAVE ALWAYS HAD..

P0483 which we all know is the fan speed
PO541 which is the brake light

Resuming on as normal i drove the truck to work in 112 degree texas heat weather... and noticed the temperature was hotter than normal, and i could not hear the fan clutch come on, and well, the AC was useless... great more issues, i stopped the truck and pulled over at work, and saw that the FC would just not come on, and kept tapping the FCA to see if it would get unstuck, and to no avail, truck just kept on loping on... and the relay would click like it was trying to turn on the FC and it would not go on... ech, bad wiring i thought, or the FC is toast, under a year old has warranty, no biggie, swap it out...

checked DTC, and same codes as above nothing different, and now two issues..

Recieved my new fca, and went and had it switched out, and i was present, at the mechanics, knowing that one DTC could have a domino effect on another, and with the NEW FCA, this thing loped even worse, RPM fluctuations were instead of the 50-100 rpms, 200-300 rpms, it sounded either really cruddy, or really cool, depending on which side of the glass you look through in this case... going back their was no hard startup at all, no smoke out of tailpipe and no diesel in the oil, and all injectors tested good with the computer... hence not an injector issue.. that was some sort of relief...

So under mechanics explanation and my recent hot box experience i went and got a new FC under warranty and brought it to my mechanic, whos workers are really quick and had that thing back to normal in no more than an hour..

idles smooth as glass with a new FCA and a new FC... why pay for labor twice on the FCA right? but it blew my mind that the dang fan clutch would mess with the idle...

I could see the ECM getting mixed signals, to raise and lower idle because of the trucks temperature, this being the only thing i could think of, or the wonky wires just messing with the darn thing beyond any sort of logic.. either ways im confused on it, but just glad it was fixed...

Moral of the story now is... if you have a lopey idle, it could be the FCA, but do not rule out the fan clutch...

cleared all DTC codes and all seems well now...

 

Good right up...
I have had this issue "lopey idle at start-up" on only 2 occasions over the past month (no codes). Wasn't sure what the issue might be so I thought maybe water and or air in the line. Drained the fuel filter completey, refired and fine. However, it did get to thinking that this was a prelude of things to come (as you describe here).

Again, thanks for the heads up!

 

two occasions only might be a fluke..

unless u have a two micron filter then id worry, id start with DTC codes and go from there.. not a heads up yet, but just something to consider as well...

An FCA throws no codes, but a FC does....

 

Excellent info...

I too have read that the electronically controlled fan clutch on the 03-07 5.9L Cummins can cause all kinds of problems, even a no start condition.
The electronic fan clutch can hang the ECM or the ECM power bus.

If you get a fan DTC & then engine running issues, I recall that a good problem determination step was to unplug the fan clutch.
Then the engine may start or run properly even though the fan clutch DTC will still be present.

 

Note: Not hijacking the thread, just sharing a same experience.

I had similar issues with my 04.5 with just over 200,000 miles. Original everything, except for batteries and lift pump. Always changed filters, oil, etc. at 5,000 mile intervals. The engine would seemingly lose all power while driving down the road at cruising speed, or even slow parking lot driving. The engine would pick back up almost instantly, or go herky jerky a couple of times before going back to normal. Engine light would come on, check codes showed P0483, P2121, P2122. So I thought the easy quick fix would be replace the accelerator sensor. Wrong. Problem persisted. I checked all wiring connections, removed all black tape on all wires under the hood, including the ones near the a/c compressor and oil filter area. Individually insulated, taped, and plastic wire loomed every wire I could get to. Problem still persisted. Then, the engine became real lopey, white smoke at startup, heavy diesel smell in exhaust. Used a Fluke IR camera on the exhaust to determine that two cylinders were burning hotter than the other 4. Replaced 2 injectors. Engine ran much better and smoother, no more lopey problem, but still had herky jerky intermittent problem. Replaced the fan clutch, water pump, and fan belt while I was at it. P0483 went away, P2121, and P2122 still persisted. Still had herky jerky problem very intermittently. Read about issue with the grounding strap on driver's side of engine, between the engine and the fire wall. Connections were tight, but noticed that the woven wire ground cable had a couple single frayed wires near some wire plug connection on that side of the engine. So I plastic wire loomed the ground cable and the insulated wires separately. Herky jerky problem has completely gone away now for the last 3000 miles.

Hope this helps someone.

 

Electronics can be h@ll! I've heard stories twenty yrs ago from a trans shop owner/friend that were almost unbelievable to me. A mopar car that burnt up the OD solenoid cuz it was broken down with the e flashers on. A ford that had bad shifting problems cuz the wiper motor was dragging. Now those stories are no surprise. Craig

 

I have had sort of the same problem with codes P0088, P0629,P0341. Started a trip to Calif and the motor just keeps stopping. If I turn the key off while still moving and turn back on it will run fine for awhile an then do it again. It has done it a couple times before but is now worse. I just replace the FC about 5000 miles ago. Guess I will check the wires and see.
Unplugged the FC (fan clutch) seems to keep running. So this means I have to replace the Fan Clutch? NO LOOKING FORWARD TO THAT AGAIN

 

P088

my dads did something similar to yours, it would shut off at rounding corners or stop signs, I replaced the FCA in that one and the problems was solved on that one.. NO other DTC codes were present tho, as far as your other codes, the 0629 and 0341, the FCA could be a domino effect, but i have not experienced or solved those.. so I am of no help there...

ALSO.. a bad FCA, will not always throw a code.. My brothers had the lopey idle, and a replacement FCA solved that issue right away.. NO other DTC codes were present tho...

also it makes no sence to me,, IF you unplugged your FC, without any power.. how is it still running?

totally irrelevant to the above statement.. BUT you might wanna check your grounds and wiring as well, before you dive into the FC.... something does not seem right at all

 

My brother..

read up my past posts.. ive dealt with this in the past before.. and this one is NO FUN AT ALL.. did you loom up the wire thats by the AC compressor? Orange in color in my 05, that causes a TON of problems if rubbed through on the chassis? also, check all of your connections to the harness and ECM... ZIP ties work wonders in keeping them together...

 

well went thru all the connections pulled apart and put back together. Did find a wire from the fass pump shorting out on the starter fixed that and tied it up away from anything. Have put about 1000 miles and no problem still going to replace the fca tho still has a lop which I have had for awhile.
Thanks for the help