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roybelding
roybelding, Shop Foreman Freightliner trucks
Category: Medium and Heavy Trucks
Satisfied Customers: 4978
Experience:  Shop Froeman for Freightliner Trucks
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Am having trouble with 1995 MCI coach detroit diesel series

Customer Question

hello, am having trouble with 1995 MCI coach detroit diesel series 60 and allison transmission b500, it wont accelerate nor engage on shift, all I get is a blinking 6 on the buttons
Submitted: 1 month ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 month ago.

My name is ***** ***** I will assist you with your question today.

I'm an independent contractor and I don't get paid until a rating has been made.

We can go back and forth as needed to help resolve the issue you are having. Follow ups are free after ratings, so rate in confidence!

CLICK HERE and follow these steps to pull the codes on the allison and give me the codes please?

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You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see, touch, smell, hear the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.

Once an answer is provided, you should see a rating screen. Please rate my personal service to you. The ratings are my personal feedback, they are not the site feedback.

Thank you for allowing me to assist you through Just Answer!

Jeremy

Customer: replied 1 month ago.
nice to meet you Mr. Jeremy, there are no codes, all i get is: OL, --, ok, that i guess is good oil level
Customer: replied 1 month ago.
should i rate you now? or when we done?
Expert:  Jeremy replied 1 month ago.

That is correct.

Now if you push the top left button, the menu button, it will cycle to give you codes.

The down arrow will also do it if you don't have the menu button. otherwise there are no transmission codes. That then makes the issue power related going to the transmission which is eitehr a battery connection issue, a fuse issue, or a harness issue. Lastly it could be a bad fluid/filter issue if it hasn't changed for awhile.

Rate when you are comfortable.

Customer: replied 1 month ago.
I have plugged the allison diagnostic software and there is no fault code at all, checked all the power lines and theyre are all good, when i get to see the tps position in parameters with my foot fully aplied to the accelerator it says: 0%
Expert:  Jeremy replied 1 month ago.

TPS is bad. It shouldn't read 0%/ It should read 99% is to floor.

Also, when foot off pedal, TPS still shouldn't read 0%. It should read "idle" indicating the idle validation in the TPS is triggered. The Allison has 2 wires for it and it is what sounds like the fault is. The Allison isn;t reading the TPS causing the gears to no engage. Change the TPS out.

Customer: replied 1 month ago.
ive, changed it with a good one, and theres is no diference still the same, i took the engine ecm and try it on a truck, and it worked good, acerlerated the way it is supposed to.
Customer: replied 1 month ago.
ive, changed it with a good one, and theres is no diference still the same, i took the engine ecm and try it on a truck, and it worked good, acerlerated the way it is supposed to. ohh other thing, the f1 pin on the vehicle harness side of the engine ecm says tps inhibit (ground) so i take a relay off and it would go (open) and there it accelerates and show percentage on the detroit diesel diagnostic link, but it wont show the percentage on the allison diagnostic program
Customer: replied 1 month ago.
theres another thing, in order to move forward you have to push D and you get the D on the buttons panel, and thats how you know your gonna move, in my case, you push the D and all i get is a blinking 6
Expert:  roybelding replied 1 month ago.

do you still need help???

Customer: replied 1 month ago.
Sir.
Expert:  roybelding replied 1 month ago.

ok, what are the voltages to the throttle pedal sensor???

Roy

Customer: replied 1 month ago.
hello Roy, theres 5+ volts on A pin
Expert:  roybelding replied 1 month ago.

ok hook it up and back probe the other wires for voltage

this is a 3 wire connector??? or is it 4???

Roy

Customer: replied 1 month ago.
this is f1 pin on the vehicle harness side on the engine ecm, as long as that input is ground, it wont accelerate, just dont know whats doing it, some kind of transmission protection or the bus body?
Customer: replied 1 month ago.
thats b an c , its a 3 wire connector
Expert:  roybelding replied 1 month ago.

monitor the voltage on the signal return wire with the connector hooked up and you moving the pedal up and down.

those voltage checks are still without being hooked up. please do the voltage check I requested

Roy

Customer: replied 1 month ago.
i did the test with the connector hooked up, pin A still 5 volts, as i accelerate the voltage increases on pin B
Expert:  roybelding replied 1 month ago.

it cannot increase beyond the reference voltage

Customer: replied 1 month ago.
what inhibits the accelerator on this bus? what grounds the F1 on the engine ecm?
Expert:  roybelding replied 1 month ago.

all controls are done through the ecm

what was the voltage at pin b before you pushed the pedal??

Expert:  roybelding replied 1 month ago.

as far as the inhibitor, you have either a bad used tps, which I got from the previous conversation, or a wiring issue between the pedal and the ecm

Roy

Customer: replied 1 month ago.
have you worked on MCI coach before? even tough it doesnt accelerate the transmission would have to engage still!
Expert:  roybelding replied 1 month ago.

yes, and not without info from the tps.

Customer: replied 1 month ago.
theres a relay on the driver side on the outside that says ABS when i take it off, it would accelerate! and you can see the tps percentage on both, allison diagnostics and detroit diagnositc link.
Expert:  roybelding replied 1 month ago.

ok, did you start it and see if it accelerates and goes into gear???

Roy

Customer: replied 1 month ago.
not pushed, half way, and full, it accelerates good but it wont get in gear, usually when you push D you would get D on the little screen and then you move, now all i get is a blinking 6 and wont do a thing
Customer: replied 1 month ago.
now that i took the relay off it accelerates good, no gear, just a blinking 6
Expert:  roybelding replied 1 month ago.

ok, the screens showing the good readings are the allision program or the engine program??

Customer: replied 1 month ago.
both of them, the one with the red bar percentage is detroit and the other on the list is the allison
Expert:  roybelding replied 1 month ago.

ok, if the ecm is reading and the tcm is not, then you have a wiring issue. this issue involves the abs. you will need to inspect the harness for the failure.

Roy

Customer: replied 1 month ago.
do you have the diagram?
Expert:  roybelding replied 1 month ago.

no, too old for my system.

Customer: replied 1 month ago.
what diagram do you have for this bus?
Customer: replied 1 month ago.
what are the lines that goes between the ecm an tcm
Expert:  roybelding replied 1 month ago.

communication networks are what the ecm and tcm share. all modules talk through these networks.

Roy

Customer: replied 1 month ago.
i know what they are, do you have the wire numbers and pins on both computers? where can i find this info?
Expert:  roybelding replied 1 month ago.

I cannot get them as I said the coach is too old.

I will opt out since I can no longer help. you need to open the harness and follow the wiring.