Transmission Module won't light up, preventing normal engine start.

[Erik Erickson]

Hi All,
I just purchased a 2003 M1078A1 from Govplanet. Upon delivery it was said that the Transmission Control Module may have an issue. I charged up all 4 batteries successfully. With the normal start up procedure, it would not start. Dash lights came on normally. I removed the starter relay, jumpered it, and the engine fired right up with the push button on the dash. I heard the transmission control module may be the problem. I pressed some buttons on the transmission module to see if it was operational without the display, but no luck. Nothing worked. I shut down the engine and came in to post here.

Any help is greatly appreciated.

 

[NDT]

Check all the connections between the display and the WTEC. Check breakers feeding the WTEC. Check connections plugged into WTEC. If everything checks out, send your WTEC for diagnostics to Transmissioninstruments.com. Yes the WTEC must be alive to allow engine cranking.

 

[Ronmar]

CB 79 provides 24V ignition to P116-4 on the controller under the passenger dash. CB 43 provides 24V battery power, to P115 pins 1 and 16 At the controller…

and as mentioned, lift the dash panel and check the connector at the keypad also…

 

[Erik Erickson]

Check all the connections between the display and the WTEC. Check breakers feeding the WTEC. Check connections plugged into WTEC. If everything checks out, send your WTEC for diagnostics to Transmissioninstruments.com. Yes the WTEC must be alive to allow engine cranking.
[/QUO

CB 79 provides 24V ignition to P116-4 on the controller under the passenger dash. CB 43 provides 24V battery power, to P115 pins 1 and 16 At the controller…

and as mentioned, lift the dash panel and check the connector at the keypad also…

Thank you both for responding!

I don't know what P116-4 is on the controller, but I'll look under the dash for it. The kick-panel at passengers feet?
I was also noticed CB66 which also mentions the Trans ECU. Should I be concerned about this one as well?

So if I understand correctly...
1. Check the CB79 and CB43 to ensure they are functioning correctly in the panel.
2. Check the controller under the dash for P116-4 and P115 pins 1 and 16 to ensure they are getting power.
3. Remove Steering Wheel
4. Remove Dash to access Trans Control Module (WTEC)
5. Check WTEC connections
6. Reassemble

 

[Mullaney]

Hi All,
I just purchased a 2003 M1078A1 from Govplanet. Upon delivery it was said that the Transmission Control Module may have an issue. I charged up all 4 batteries successfully. With the normal start up procedure, it would not start. Dash lights came on normally. I removed the starter relay, jumpered it, and the engine fired right up with the push button on the dash. I heard the transmission control module may be the problem. I pressed some buttons on the transmission module to see if it was operational without the display, but no luck. Nothing worked. I shut down the engine and came in to post here.

Any help is greatly appreciated.

.
Hi Erik,

Welcome to the outfit and your new adventure in ownership of a big green truck! Seems to me that the guys have you headed off in the right direction. Be sure to download the TMs (Technical Manuals) for your "new to you" truck. Lots of troubleshooting information in those crusty boring books. The Allison WTEC manuals are also available for download too.

 

[Ronmar]

Under the passenger dash you will find the wtecIII controller. It has 3 plugs on it. They should have metal tags/bands around the wire bundle on them identifying them. On the III the keypad is just that, a pushbutton user interface. You shouldn’t have to remove the wheel, just loosen the adjuster knob on the left side and pull it up as far as it will go and tilt it as far back as far as it will go(tilts and has about 3” of height adjustment for driver comfort). Then you can lift the dash far enough to access the keypad connector…

not sure about cb66, let me look it up…

EDIT: CB 66 is for blackout lighting… not sure if that interacts with the display lighting, but it would not effect the ability to operate, only the ability to see the display…

 

[BERZERKER888]

Gov Planet.... there's your problem

 

[Erik Erickson]

Under the passenger dash you will find the wtecIII controller. It has 3 plugs on it. They should have metal tags/bands around the wire bundle on them identifying them. On the III the keypad is just that, a pushbutton user interface. You shouldn’t have to remove the wheel, just loosen the adjuster knob on the left side and pull it up as far as it will go and tilt it as far back as far as it will go(tilts and has about 3” of height adjustment for driver comfort). Then you can lift the dash far enough to access the keypad connector…

not sure about cb66, let me look it up…

EDIT: CB 66 is for blackout lighting… not sure if that interacts with the display lighting, but it would not effect the ability to operate, only the ability to see the display…

OK, great info. I'll post with updates.

 

[Suprman]

Tcm gets fried when you try to jump start with dead batts. Its under dash behind the passenger kick. I have replacements.

 

[Erik Erickson]

Tcm gets fried when you try to jump start with dead batts. Its under dash behind the passenger kick. I have replacements.

That is what I think happened here... Cost?

 

[Suprman]

500

 

[Mullaney]

Tcm gets fried when you try to jump start with dead batts. Its under dash behind the passenger kick. I have replacements.

.
So, Will... Does that add another reason to drive these vehicles regularly?
Or maybe if you can't do that or don't have time - maybe a trickle charger on the batteries over the winter?

 

[Suprman]

For some reason when you jump a truck with dead batts it spikes the wtec3 tcm. Dosnt seem to do it to the wtec2 trucks. You can charge dead batts and its fine its the “batts stone dead and jump start the truck without letting the batteries get any charge”

 

[Mullaney]

For some reason when you jump a truck with dead batts it spikes the wtec3 tcm. Dosnt seem to do it to the wtec2 trucks. You can charge dead batts and its fine its the “batts stone dead and jump start the truck without letting the batteries get any charge”

.
Thank you sir!

 

[Erik Erickson]

500

OK, I have the old TCM out. How can I purchase this from you?

 

[Suprman]

Send email to will at lmtvparts dotcom send pic of your tcm label. I can send PayPal invoice if you have PayPal
Will

 

[Erik Erickson]

FYI, thanks for all the help. TCM replacement worked to get it moving. Thanks.