Freightliner LBCU Issue?

[paintedtugboat]

Yesterday morning we broke camp in the usual manner and cranked up the Cummins. Almost immediately The LBCU read out said "!High Battery Voltage" and the idiot lights ABS (yellow) and Transmission (yellow) stayed on. The readout then read "!Check Trans". I continued with start up and when I had completely aired up and saw that the engine temperature gauge was coming up, I shut down for a minute to see if it would reset itself. After restarting both the ABS light and the Transmission light went out but The readout still read !Check Trans. To see if I could gather any other information, I began to toggle through the LBCU which seemed to clear it. I put it in gear, hooked up the toad and very gingerly set out. The Allison performed as it always has as did the engine. I left the read out on transmission temp to monitor it. No further warnings on the read out and no other idiot lights came on for the remainder of our 4 hour trip.

I had a yellow check engine light come on twice before but Freightliner could pull no fault codes on those.

So do I have a real problem or just another LBCU hick up?

[UsualSuspect]

If the chassis battery voltage is low you will see the high voltage warning. The ABS light is another sign the batteries were close to discharged. You probably had just enough juice to start it. The charge voltage will go back down once the batteries start charging up. If I don't start mine at least once a month, or run the generator mine will do what yours did. I took mine to a CAT Mechanic and he said they were not meant to sit, and I should drive it, or charge the batteries every few weeks.

[paintedtugboat]

Thanks, everyone for the help.

I pulled the error codes from the Allison 3000 transmission. d-1 had in memory a P0883 error which is, according to the Allison website, a "TCM Power Input Signal-High". That was the only code in d-1. d-2 through d-4 showed no codes.

The TCM gets its power from the chassis batteries, is that correct? If that is the case, I am wondering if the chassis batteries are getting over charged which, I believe, is a sign that they are starting to go bad.

Any comments are appreciated.

Bob
2010 Tiffin Phaeton 36QSH

[eheading]

Brett, I believe you can only do the Allison diagnostics on the 3000 series trans. I don't think it works on the 2000 series transmission. Is this right??

Ed Headington

[ScottG]

It complained about supply voltage being high. Did you check battery voltage?

[wolfe10]

Easy to check transmission for codes (from the driver's seat with no tools):

Turn key on/engine off.

On the Allison shift pad, press up and down arrow at the same time. If newer coach, that will bring up OL (oil level). If older coach it brings up d-1.

If newer coach (see how a signature helps), press up and down arrow again to bring up d-1. If there is a Diagnostic code it will flash d-1 then a code. If no code it will flash d-1 followed by - -. If a d-1 code, write it down and hit the mode button to bring up d-2. Repeat until - -. Push D to exit.

Look up codes in your Allison book or on Allison's website.