Need help troubleshooting an issue with my WTECII

[Coffey1]

That sensor on bell housing does nothing but drive the tac on trucks that have a tac.

 

[Ronmar]

Yes, the output speed sensor is used by the TCM before it is output to the speedometer. In the section for troubleshooting 25 series faults in the Alison troubleshooting manual gives a few other reasons for the 25-11 code, like an inaccurate turbine speed sensor output...

 

[Ronmar]

That sensor on bell housing does nothing but drive the tac on trucks that have a tac.

Correct! The Allison has its own RPM sensor down on the lower right front of the transmission housing...

 

[spankybear]

One heck of a ride troubleshoot this issue. I started on the power side and took a close look at the circuit breakers. They looked awful and a couple fell apart. Did a resistance check and a couple had high readings. Off too the store to get some fuses. I thought for sure I found the problem. Get the fuses in and now the truck would not start. Ok I learned that you need to switch the head light switch off. I didn't know it energized one of the relays. Now I have a dead batteries. Wanting to get this truck started I grabbed 2 chargers I have. One a smart charger and one an old school. I hook the old school charger up and looked the the current draw... 10 amps... about 10 mins later its down to 1 amp. One of the things I tested was the batteries. This one, while a little weak passed my tests. But I do not have a load tester. Off to the battery store thinking I had a bad battery. Get it load tested and its junk. Funny that all cells had good specific gravity and good internal resistance. Now I thought for sure I found the issue... get the replacement battery and the other charged up and get the truck started. Took her for a spin and no shift... setting code 25 11.... well I found 2 problems but not the one I am looking for.

So on to check the speed sensors . I pull the dash a part and get to the "B" connector to check the speed sensors. The all had what I would expect on the meter. So nothing there. Then I look at the power and ground on the "B" connector. All looks good. At this time I needed to stop looking and on to something else. I have found that when you are running in to dead ends I need to do something else for awhile. I had bought a new buzzer for the truck because the one in the truck was bad. I got one with a "volume" so it would not be so loud and I didn't want to use 100MP{H tape on it. As some may know these buzzers are 2 tone. I wanted to use the beep side for the air warning thinking it would be less annoying. I look down at behind the cluster and then I see that the "a connector had fallen out of the TCU. I thought that maybe the connector clip had broken. Nope it fine. I guess I didn;t get it latched when I installed the cluster. I made sure to press them in firm this time....

I get the cluster placed back in and time to test it out. I do like the new tone from the buzzer and that I can "lower" the volume. It get up to pressure and I take it for a spin... It shifts again!!!!! woohoo!!!

I want to thank you guy for your tips. I may have not found the other issues if I didn't look at the power. I am sure those would have come up somewhere along the way.


Thanks again!!!

 

[NDT]

The connectors can slip out of the back of the trans control when you are putting it back in. There are tabs that lock the two of them in place sometimes they break off or just dont lock in all the way.

DINGDINGDING!!!

 

[MrGoodwreck]

Sweet!

She runs, and shifts..

Now whats next?

 

[Ronmar]

a badly sulfated battery will have good specific gravity and cell resistance. It just doesn't have very much plate actually exposed to the electrolyte So falls on its nose when a load is placed upon it...

Glad you found the trans issue...

 

[Coffey1]

Hooray love it when trouble is found and we get a report back on what it was.