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William, Fleet Manager
Category: Heavy Equipment
Satisfied Customers: 46
Experience:  OEM trained Allison, Detroit, Cummins, OEM ONAN capability, OEM Carrier AC Dealer, 27 years exp. DOT
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Type of bus Van Hool cummins engine 500hp..diagnostic tool

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A charter bus. Type of bus "Van Hool" cummins engine 500hp. I still need to buy a diagnostic tool. which tool
do you recommend? Also keeps shifting down by itself and will not shift to any other gear. unles i turn off and
restart. What could be my problem?

Good Morning,


I would like to try and help with your current problems.


I need to know the engine serial number, as well as the Transmission model and serial number. Is it an Allison?


Thank you,



Customer: replied 7 years ago.
transmission-WTB500 (R) Allison ZF- Astronic
Engine-ISMO2 400

multiplex system-siemens VDO
Sorry i don't have engine serial at this time. hope this helps

The B500 has diagnostics built into the key pad.


Turn the Key on, at the key pad for the Allison, push the up and down arrows at the same time, this will put you in diagnostic mode.

Display should show D-1 then a four digit code. Write these down.

Then hit the mode button, this should show D-2, keep doing this and record all codes listed.

Once you ran a code check on the transmission, let me know what you find.


Allison will force the lower gears and even lock you into range if there is a problem.


Customer: replied 7 years ago.
I don't have the vehicle with me. yesturday i performed this test on it. If i remember well the codes were-

I'm sorry, I dont show a 15-16 or 15-11 code for the Allison B series.


Customer: replied 7 years ago.
I will have to leave question open for until I retrieve codes on monday.

I will keep an eye out for your next posting.


Thank you,







If it will help you, I add the Allison Code Manual to my answer. If you get codes that match, I can follow up with the information to support that codes test and repair.


Your request timed out, but below is a direct download of the Allison Code Manual if needed.


"Click HERE for the Allison MD PDF Code Manual"

Customer: replied 7 years ago.
Sorry for the long wait. the codes were- D1-2216, D2-2511
Thanks for the chart of transmission codes. Which relates me to the output speed sensors.
As mentioned before, I replaced all three sensors; and ohm them. Also ohm them at ecu connector
still 3000 ohms. Wiring at sensors look in good shape i don't feel a lot of vibration on driveshaft.
Bus runs good for a few trips, but problem returns.

I will get the book out and copy the code testing and repair pages for these codes.


Give me a little bit. Will get it loaded shortly. If all this helps, please accept my answer and let me know if there is anything more you need.


Thank you,






I'm sorry, I was wrong, the book I have is the parts book. It will be tomorrow morning before I can get you the Testing information related to your code.


Thank you,





Good Morning,


Well the book only has you check for an open between the snsor and the computer.


Most of the time, the problem is found at the main connector just a few inches from the transmission. I have also seen the tone wheel come loose in the Allison causeing problems. Hope this helps,




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