| Author |
Message |
Bob Wood (205.188.200.23)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 1:37 pm: | |
Went out to start the bus yesterday, turned on the battery master, the engine and trans check lights came on as normal, and the engine check light then went out, as it should if no problems are detected, but here's the PROBLEM. The check transmission light stayed on and I cannot get the bus into gear as long as the light is on. After saying all that, what can I check, or what is the computer monitoring that might cause this problem. Are DDEC Readers available to buy? I've checked the trans. fluid, and it's okay. I'm located in Clarkston Michigan, if someone knows of some help they can send my way. I'm pretty much dead in the water. This is a NJ Eagle 20. Any help or advice would be greatly appreciated. Thank you.
Bob. |
Ed Way (12.218.204.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 2:20 pm: | |
You might try disconnecting both battery cables and then reconnecting. Sometimes this will reset the computer.
If I read correctly the bus started. Did you get the parking brake to release and still have pressure of the foot pedal while trying to put in gear?
I don't know if the fast idle would affect it or not but it might
Also try the engine override switch and see if you can get in gear while holding on the engine override, that should cancel the computer code while you hold it.
Sounds like you might have a bad sensor on the transmission and I do not know exactly where that may be located. |
Bob Wood (205.188.195.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 2:49 pm: | |
Yes, the engine starts. I will try to disconnect the battery cables. The fast idle operates properly. The sensor is what I would like to find, but what is it monitoring? If it's monitoring fluid, the fluid is okay, but like you said it may be faulty. Let me add something that may be related or not. I removed the electric starter solenoid, and inadvertantly sparked the hot lead to ground for a second. This lead is connected directly to the batteries, however, could this have tripped the computer to fault the transmission. |
Greg Roberts (Gregeagle20) (172.139.31.55)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 9:41 pm: | |
Bob,
There is another solenoid on the back wall that ports air to the retarder on the Allison transmission that will give you a fault code if it has failed. However, I don't believe this will keep you from being able to place the transmission into drive or reverse. One hint, the Allison has it's own computer (ATEC) and is completely independent from the DDEC. You can read the flash codes using the dignostic switches. I may have a a list of the codes out at my warehouse but you can also get them from any Allison dealer. Hope this helps. |
Bob Wood (152.163.201.68)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 10:26 pm: | |
Thanks Greg, do you know where the ATEC computer is mounted. I believe the DDEC Computer is on top of the engine, but don't know where the ATEC is. I'm not familiar with the diagnostic switches. Are they located on the computer? Sorry for all the questions, I just don't see the computer in any of my manuals. |
Ed Way (12.218.204.43)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 28, 2002 - 10:48 pm: | |
Other then a disconnect from the battery I do not know of any other way to reset the DDEC without a reader and they are very expensive. The DDEC will store both active and inactive faults.
I'm guesing that the cable short could cause a fault but it should not show as an active fault. Only the active faults should cause engine shutdown.
Since the engine runs the ddec probally does not have an active fault. Guessing again the transmission check light is probally from a temperture sensor. That sensor would most likely be into the tranny pan. |
Bob Wood (67.38.95.18)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 29, 2002 - 9:09 am: | |
Thanks Ed for all your input. |
Greg Roberts (Gregeagle20) (66.7.134.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 29, 2002 - 1:31 pm: | |
Bob,
The diagnostic switch and light should be on your dash. The process is pretty simple. Turn on your master, wait for the computers to cycle, move the switch and hold in the transmission position, count the light flashes. The light flashes sequences have predetermined meaning. The list of these codes may help you more surely determine the root cause of your problem. I would have to agree that the temperature swith would be the most likely culprit but guessing can cause delay and extra expense. |
Bob Wood (67.37.66.126)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 29, 2002 - 2:48 pm: | |
Greg,
I ran a diagnostic check and came up with a code of 34. Called local Allison dealer, and they were real helpful. The code reads "Prom Check." The dealer thinks maybe one of the proms has come loose out of it's socket. So my next step is to remove the computer and reseat the Proms.
Thanks for your input. Any other thoughts greatly appreciated.
Bob. |
Greg Roberts (Gregeagle20) (66.7.134.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 29, 2002 - 4:46 pm: | |
Bob,
I believe the PROM in the Allison is actually a EEPROM. An EEPROM is an Electrically Erasable Programmable Read Only Memory. This means that you can download a program into the chip and it will perform logic functions in an automatic fashion to control the transmission. This also means that as much as a spark of static electricity can write to the EEPROM and change the binary code. Three points I would make: 1) you should where a static strap to equalize any electrical potential between you and the computer to avoid damage to the program 2) do you think that your arcing event might be the culprit for somehow corrupting your transmission EEPROM? Did the problem appear exactly at the point in time? The odds of the Prom loosening at that very moment are fairly low I would think and that is why I question the arcing event. 3) are you 100% sure that you are reading the code correctly?
If the EEPROM program is corrupt then you will need to have Allison connect a PC and write the program into the EEPROM again. It will take all of a few minutes once they decide which program to install and grab it from their corporate mainframe. Good luck! |
Bob Wood (67.37.79.203)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 30, 2002 - 8:39 am: | |
I would like to thank everyone for helping with my ATEC Trans. problem. I removed the computer, and brought it to my shop, I'm in the aviation electronics repair business, and I disassembled the computer, inspected, and removed the EPROM, retensioned the socket, cleaned the computer connector pins, and reassembled. I reinstalled the computer, applied power the YAHOO!!! The self test passed, and everything worked great. Thank you again. It's really nice to get such great answers to my posts. This is a great board.
Bob. |
Greg Roberts (Gregeagle20) (66.7.134.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 30, 2002 - 6:09 pm: | |
It's always nice to be a part of the solution and zero expense to repair is awesome! - Greg |