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Topic: Transmission brake signal - Allison fault code 6340 (Read 2711 times) previous topic - next topic

Transmission brake signal - Allison fault code 6340

I got error code 6340 on my transmission... according to the Allison manual this means that it's missing the service brake signal.

I checked the wire diagrams and found that there must be a normally open pressure switch somewhere that detects the air pressure on the brake line.

But... does anyone know where on the coach this sensor had been installed? I could find quite a number of sensors on the brake airlines, but I could not tell which one the transmission wants to use... any ideas?

Cheers,
Matt
1998 U270 3402 WTFE #5260
Cummins 8.3l - Allison MD3060
600W Solar :P

Re: Transmission brake signal - Allison fault code 6340

Reply #1 –
Here's a couple of photos of what Ralph is referring to. I replaced these pressure switches to cure a cruise control issue that relied upon the brake signal.
jor

93 225
95 300
97 270
99 320

Re: Transmission brake signal - Allison fault code 6340

Reply #2 –
Not familiar with that fault code.  Ralph is pointing to three Allison air brake pressure sensors that tell the ECU how much Retard to turn on when pressing brake pedal.  Those pressure switches also connect to Retard joy stick wiring and then connect to the ECU.

Re: Transmission brake signal - Allison fault code 6340

Reply #3 –
Matt, take a look at the back of the park brake valve I think you will find the pressure switch.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Transmission brake signal - Allison fault code 6340

Reply #4 –
Quote from: bbeane –
Matt, take a look at the back of the park brake valve I think you will find the pressure switch.
that's the parking brake switch, I'm looking for the switch that tells the ATEC module that I'm hitting the brake pedal.

Thanks to above inputs I finally found it in the drawing, will keep on searching for the physical location. Must be somewhere near the three retarder brake switches...




1998 U270 3402 WTFE #5260
Cummins 8.3l - Allison MD3060
600W Solar :P

Re: Transmission brake signal - Allison fault code 6340

Reply #5 –
Matt,

I will attempt to guide you in the right direction, I don't have a pic. of this.  I have been tied up on an A/C compressor problem on a members coach and I missed your thread.

You need to run the drivers seat all the way to the rear. Now lay down and remove the heat duct that is attached to the kick panel in front of where your left foot would be while driving.  Now that carpeted panel will pull off to the rear of the coach. There is just enough room (if you hold your mouth right) to remove that panel from behind the steering column. Take a flashlight and look up between the steering column and the dash frame and you will see the pressure switch that I think you are looking for.  It is attached to an air line under there and the wires that come off of it will go to the drivers side of the coach and hook to the trans ECM that will be able to be seen after you have removed the kick panel ( the side kick panel is part of the front kick panel so it will come out all in one piece)  Also as a side note you will find both retarder interface boxes hid in this same area. Give this a look and see and let me know what you find.

Once you find it you may discover that the plug has been kicked loose from the pressure transmitter.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Transmission brake signal - Allison fault code 6340

Reply #6 –
Thanks Pamela & Mike!! I found the sensor, measured it and it seems good. As soon as I touch the brake pedal it closes, then opens once I let go...



cleared the error code now and will see what happens tomorrow when I'll do some more driving.

Will keep you updated, thanks!!

Matt
1998 U270 3402 WTFE #5260
Cummins 8.3l - Allison MD3060
600W Solar :P
 

Re: Transmission brake signal - Allison fault code 6340

Reply #7 –
Matt,

If you put that kick panel back in place and the problem returns. Check to see which wire has been put in a bind. You may have a wire connector that is loose or a wire that has developed a faulty spot.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."