problem solving

[jgssm]

Hi,

I have a Mercedes R class 320 L W251on a 2006, a couple of weeks ago I had a rear brake pipe fail and had to abandon my car at another address in our town.
The local garage looked at it and was not able to start or move the vehicle.

It was stuck in park as we could get no brake pressure to take it out of park.

We decided to make a temporary repair in the leaking pipe and now have full brake pressure back.

Now the car will not even turn over. Batterie is good, all dash lights come on, but no response from the key when turned.

I used my iSOFT MB2 diagnostic equipment and I Have found the following,



The Intelligent Servo Module (ISM) area I found a code 1939

No con message was received from control unit y3/8n4 fully integrated transmission control UGS control unit.

Questions

Would this stop the car from starting?

Why would loss of brakes cause this code?

Do any of you knowledgeable people know how it could be fixed?

Many thanks.

 

[mioba]

Have you refilled the brake fluid assuming some
was lost and bled the brake line.

Did you clear the code and try the car again

 

[jgssm]

Have you refilled the brake fluid assuming some
was lost and bled the brake line.

Did you clear the code and try the car again

yes, the garage did the brake lines and got pressure back.
then I went through all areas and cleared all faults. this is the recurring fault .

 

[EmilysDad]

.....

It was stuck in park as we could get no brake pressure to take it out of park.

....

Surely it's just a feed from the brake switch that allows it out of PARK .... no pressure required ??? Certainly was on my Omega cos I ended up needing a new switch ..... it's embarrassing sat at the lights with a queue behind you & you can't get the car out of PARK

 

[dry run]

Do you have any breakdown cover? Most will move the car to a garage.

 

[LostKiwi]

Loss of brakes would be unlikely to cause that error.
The reference to y3/8n4 is the Transmission control unit. The ISM isn't getting a CAN signal from the TCU. Check the fuses to see if there is anything blown (can't remember if there is a separate one for TCU). Failing that try disconnecting and reconnecting the ISM (on the side of the gearbox) in case there's a bad connection. The ISM is used to instruct the gearbox which gear to select from inputs at the selector lever.