M1078 Allison HD3070 Shifting Problem

[Lugnuts]

I will give the problem first and then state what I have done for diagnostics.
Problem- Transmission when put in drive lights up with 7 gear showing in left window and 2 showing in right window.
Drive and will not shift to 3rd even when tached out.
Stop- Shift it manual in to 1st- it goes into first- Manually shift to 2nd- try shifting manually to 3rd- it will not shift
Stop- Reverse- It's there- Back into forward- 2nd and no shift to third.

Diagnostics- Had checked oil and a probably 2 to 3 quarts low but on the stick
Triggered code reading and found 4 codes
D1- (21-12) TPS (Don't be so quick to judge)
D2- (35-00) Battery Voltage interuption
D3- (33-20) Sump fluid sensor failed
D4- (24-23) Sump fluid temp hot - no upshifts
Cleared codes and one remained active that being D1- TPS
Checked my Fuse Panel to see if I had any tripped fuses- None
I then read I believe on Steel Soldiers possibly in the manual that even if you have a bad TPS that it will shift by default at a certain designated RPM. This I cannot verify in my personal experience or knowledge.
The other codes did not come back so this is where I am and my next place is to come here.

Again I do appreciate your help and I have to say that if left to my own devices and skills I would replace the TPS next and if that didn't take care of it check that wiring between the ECU and the TPS Actually writing it down I probably would check the wiring using the TPS that I have in there already and check both with one test.

PS. I replaced this transmission about 2 years ago with a Weller Rebuild and it worked flawlessly. I had also just driven this truck two weeks prior after fixing the Rear Brake Relay and all was in order. This truck is kept outside under a shed but varmints still have access but no evidence of anything, just mud robbers.

Thank you

 

[Ronmar]

It should upshift if a peak RPM is exceeded. But that peak RPM set point may be greater than your current maximum governed RPM. Without TPS, the trans control does not know your desire to accelerate.

You will need an ohmmeter to check its resistance and see that it varies with throttle linkage movement, then you can re-calibrate it...

I did a video...

 

[Suprman]

The battery voltage code is the one you want to hunt down first. Replace relays clean breaker panel tabs. Polarity box connections etc. Low voltage or loss of will cause all kinds of codes.

 

[Lugnuts]

It should upshift if a peak RPM is exceeded. But that peak RPM set point may be greater than your current maximum governed RPM. Without TPS, the trans control does not know your desire to accelerate.

You will need an ohmmeter to check its resistance and see that it varies with throttle linkage movement, then you can re-calibrate it...

I did a video...

Thank you. I didn't even know that existed. You're alright, no matter what anybody says! LOL/ Lugnuts

 

[Micmada]

It should upshift if a peak RPM is exceeded. But that peak RPM set point may be greater than your current maximum governed RPM. Without TPS, the trans control does not know your desire to accelerate.

You will need an ohmmeter to check its resistance and see that it varies with throttle linkage movement, then you can re-calibrate it...

I did a video...

Nice video. I have an FMTV transmission laying in its box and was wondering if it would fit in a M923 for an install. Looks like it is a bit more involved in electronics and I would need to get my hands on a few modules. Now I might end up selling it or trading it in.

 

[Lugnuts]

So I went to my truck with the new found information and just knew I had this thing whipped and low and behold I was wrong. The TPS itself is working fine and with in the ranges required so I set about to calibrate and nada.
Now this of course leads to more questions and NO, not of yet have I taken a look at the wire schematic but I am going to.
Questions- Does the TPS just give information to Allison or does Allison interface with Caterpillar? And then the question about why Allison isn't getting the TPS information. No other codes came up on Allison except for the TPS and that one is present as in it won't even begin to be deleted from the D1 diagnostic window.
The next question is - In calibrating is there anyway the TCU comments on whether the request to be recalibrated is received or do you assume it did by Go or NO GO?
Last, is there scanner equipment available that instantly shows whether a request was received or not?
Thank you and join me in my adventure won't you please!

 

[Ronmar]

On the A0 trucks(with the TPS) there is nothing to interface with as they are all mechanical. That TPS IS the cat interface

The trans controller is its own entity working with sensors and solenoids on the transmission. you will need to check wiring into the trans controller to make sure that the TPS resistnce change is reaching the controller.

there is Allison software to talk to the controller or there are older scan tools to talk to it.

There is nothing to indicate the cal has taken/been acted upon by the controller after the 6 power cycles…

 

[Ronmar]

21-12 TPS filed low might indicate an open circuit.
there are two connectors on the trans controller, A and B. Depending on wether you are a wtec 2 or 3 the controller is with the keypad in the dash and it uses a Vehicle Interface Module full of relays under the passenger dash. Or on the wtec3, the trans controller is under the passenger dash where the VIM on earlier wtec2 trucks were located(no VIM uses relays in the main panel for neutral and reverse outputs).

Plug B pin 1(green wire #135), B pin22(blue wire #156) and Plug A pin 24(red #124) should be directly connected to pin A, B & C on the TPS and you should be able to do the same resistance check I showed in the video from the controller connector while stepping on the throttle pedal to stroke the TPS…

 

[Lugnuts]

21-12 TPS filed low might indicate an open circuit.
there are two connectors on the trans controller, A and B. Depending on wether you are a wtec 2 or 3 the controller is with the keypad in the dash and it uses a Vehicle Interface Module full of relays under the passenger dash. Or on the wtec3, the trans controller is under the passenger dash where the VIM on earlier wtec2 trucks were located(no VIM uses relays in the main panel for neutral and reverse outputs).

Plug B pin 1(green wire #135), B pin22(blue wire #156) and Plug A pin 24(red #124) should be directly connected to pin A, B & C on the TPS and you should be able to do the same resistance check I showed in the video from the controller connector while stepping on the throttle pedal to stroke the TPS…




View attachment 909219

I've got to get back out there and check continuity/ Thank you for the schematic/ It is much more concise than the TM schematic/ The other thing I have had happen on trucks is that wires shrink or get stressed and actually just pull out of the connector enough to leave the circuit open while looking like it is still in there/ Closely looking you can see that it is not quite seated/ I'll let you y'all know what I find/ And thank you Vets for you service, enjoy Veterans Day.

 

[Lugnuts]

So the truck is shifting now. The fix was quite easy once you know where to look. The problem was at the KeyPad. After finding that I had an active code on the TPS, and watching the video put out by Ronmar, I found that the TPS was good and that between The TPS and the Keypad I had a problem so, I removed the steering wheel and lifted the Instrument Panel out with the Keyboard and looking carefully everything looked fine. I went to remove the Connector at the back of the Key Pad and noticed that it was particularly easy to remove. I was skeptical and found that somehow the connector was not clicked in and had managed to come out just enough to not make a good connection. ( It was now at this point that I said Could it be this easy???) But it was. After clipping and repulling and tugging I cleared codes and they did not return. So Throttle was programmed the way the video instructed and by golly I am here to report that it is fixed.
Thank you all for comments and aids and I'll call out Ronmar and thank you for sharing your knowledge.
Happy Thanksgiving y'all