[Johnnyboy]

You are doing good asking questions. I see you have inquired on an Allison chat. I agree you need to fix your alternator and/or charging system. How are your batteries? Both need to be in good shape so the electronic transmission can work correctly. A lot of issues will go away with good voltage.

If you still have check transmission light, I would check your connection at the computer and transmission, disconnect and reconnect the plugs. Check or replace output speed sensor. I know you can pull the 2 digit codes being an ATEC transmission, I have never done it on a Newell, I would look around your computer for a switch and an indicator light or it maybe your check transmission light is the indicator light. I would also look in your Newell coach books to see if they mention anything on how to check codes. maybe someone else can explain the process. I had an MCI with the ATEC and they had a switch and extra indicator light near the computer where you could check the codes.