Second Opinions Welcome

[DaveNY]

On occasion my truck sets a 236 at about 71 mph, probably the solinoid which dosent usually defuel or any other noticeable symptoms and after a few restarts the light goes away.(the reason for thr T/M) This time it dragged in a U1026. I was in the hills of Pa. with the cruise on and the tranny would downshift and come out of lockup which I thought was unusual. It rarely behaves that way.
My train of thought is this may be because of the momentery P0236. Or the fact that my roadspeed was not high enough to carry the truck up the grade in O/D, about 4 1/2%-5% 50-60 mph.I encounter no such problem on any grade encounterd on the Interstate at 65-70,it stays in lockup and pulls the grade no problem. All seems OK and erased all codes no recurrance of 1026?Any Ideas
Dave

[Robyn]

The TCC can drop out if the throttle pressure becomes high enough.
I am not familiar with the OBD2 codes enough to comment on that part

[DaveNY]

Robyn,
The u1026 is some kind of interuption of comunication between the ecm and tranny. I have encounterd the lack of cruise control on failure of the pmd and such. This time It just seems that the tranny was not locked up as usual while in cruise,it would not lock when I held the decel button in as it usually does and give an engine brake effect it just remained un hooked and no drag?
Almost like there was to much going on and the tranny was confused,as was I. It resumed normal operation but I have never heard mention of U1026 on this forum.
Dave

[Nobby]

Hey Dave,
Funnily enough I started popping the 0236 a couple of times in the PA Hills also, everything checked out OK as per DTC diagnosis cured it by changing out the Solonoid as you have already summised.
As to the U1026, its a loss of communication with the Transfer Case as I understand it. Nothing in my manuals on it so I am guessing as you are a 99 you have the Autotrac setup so I am wondering if there was a glitch in wheel slippage sensing?

cheers
Nobby

[DaveNY]

Nobby,
My understanding ,which is very little about this code is that with all the activity of of the Tcc and Downshifting in cruise while navigating the steep rolling hills(pa115 south out of Wilkes Barre to I 80) caused to much comms and may have been a momentary loss of communications which set the code?
Dave

[Nobby]

Yep I see what you are saying with all the trans comm going on, I guess it is one of those hopefully not to be seen again codes.

I've been doing alot of commuting to a job in MI lately so I know I80 pretty well now. Spent an hour trying to prime my fuel system around halfway on I80 when my fuel filter cap mysteriously had worked loose only to discover that my lift pump was not working. I was just noticing that my rear screen was fogging up when she goes and quits on me. I was relieved to find it was fuel oil and not lube oil and fortunately I carry a vacuum pump which took care of that.

Incedently where in LI are you I am in Patchogue

cheers
Nobby

[DaveNY]

Islip Terrace

[tommac95]

Dave-
There used to be a lot of discussion here about the torque converter 'losing' lockup.

Another member , "Damork" installed a number of relays in the electric system to relieve the burden on switches, and undersized wiring. I'm pretty sure he installed a relay in the 4L80E wiring harness , and i also think there is an aftermarket company which sells an upgraded harness for the trans.... but i don't really recall what the issues are .

I dunno anything about the DTCs , since i've not had any yet (and i'm OBDI).

[DaveNY]

Tom,
At present I'm hoping this was a just a glitch and nothing more. I am a little surpised that there is limited info on this code. So far there has been no repeat of this event. Thanks for your Info and it will come in handy if things get goofy again.
Dave