Allison Keypad Blank

[gkaters]

This is on a Gulfstream Scenic Cruiser 1995 on Spartan 1994 Frame. Allison MD3060 WTECII control module



Testing:
I tested the Keypad/ECU with the light bulb method that Transmission Instruments recommends and inserted test lamp leads into corresponding B connector sockets: 9 and 2 then 18 and 11. Nothing lit up.

Testing VIM

With both house and chassis breakers off:

With a Voltmeter I put negative to K1 and Positive to J1 reading 12.1
With a Voltmeter I put negative to K2 and Positive to J2 reading 12.1

House Solenoid resistance was 0.00
Chassis Solenoid resistance was 0.00
Silver Solenoid resistance was bouncing around 10

Fuse shows 12.59 volts (Main Power)
Fuse shows 6.9 (Ignition)

With house and Chassis breakers on everything read the same

When I turn the key on
J1 K1 and J2 K2 voltage dropped Main Power Fuse shows 4.1 volts
Ignition Fuse shows 5.3 volts

What should I be looking at as the problem? What would cause the Voltage to drop when the key is turned on? Ignition? One of those 6 boxes in the VIM? Help

[Gixxer007]

What kind of problem are you having

[wolfe10]

Contact John,


This is what he does for a living and has for a LONG time:


https://www.transmissioninstruments.com/

[gkaters]

No power to the keypad so it won't start because it doesn't know it is in Neutral. See above for more detail

[gkaters]

Originally Posted by wolfe10

Contact John,


This is what he does for a living and has for a LONG time:


https://www.transmissioninstruments.com/

I used John's trouble shooting documents to get this far but it is not the TCU/ECU I am not getting enough power to the ignition in the VIM.

[Jon_C]

Voltage will drop with key on due to intake heater / glow plugs or whatever your motor uses to preheat before start ( assuming its diesel)

Sounds like your battery is discharged, check voltage at chassis battery with key off then on. If voltage at battery is below 10v with key on either charge or replace.
And check for loose or corroded connections at battery.

The tcm needs greater than 10v to power up.

[Twomed]

That CAT grid heater really sucks the juice. Check your batts while somebody turns the key on and you will see the big drop, keep your leads on the batt and see if the volts come back up after about a minute. You show 12.59V which is basically a full charge I wonder if you have the coach plugged in and are getting just a surface "full" charge which is getting killed by the grid heater, then you are below 10v or so and that is preventing a neutral signal and keeping you from a start???

You might pull batts and have them load tested or if comfortable with big amps jump your starter and see if the CAT will turn over. Check batt connections and clean batt and chassis grounds CAT's are serious about clean power, at least mine was. And remember volts are not the same thing as amps a surface charge might look good, but a bad batt, low amps no muscle will just not do the job.

Good Luck

[deandec]

Does the engine start?

Have you started the generator to boost the starting batteries?

Does your rig have a Start Solenoid and an Ignition Solenoid? My rig does, but the engine will not start if the Tranny pad is not lighted. That symptom was caused by a failed ground on my Ignition Solenoid. Easy fix.