Hi guys,

Im trying to diagnose a 2/4 brake duty code p0778 and it asks in the steps to check pins on jb131. It mentions pins 3 and 17. However, if I’m looking at the right harness, one located above jb155,
it only has like 10 ish pins.

Now I’m kinda stuck, I’ve searched for the diagram to no avail. Anyone able to help me get this kitty purring again?

As the problem is, it’s either a bad 2/4 brake duty solenoid, a shorted wire or the tcm (which I had to change before)

There are NO local junk yards with a compatible TCM so I’d have to order online likely from the USA to Canada and I just want to make sure I need it bc I won’t even get it shipped here for 3 weeks.

Anyone have any advice?

Thanks Fam

 

If your TCM has two 24 way plugs (White and Grey) then your car is fitted with the 32Bit module.
So for the 2/4 Brake you are looking at the White plug which is JB230 pins 21 (Blue wire - signal)) and 4 (Black - solenoid ground return).

If you have a single TCM plug (37 way Blue plug), then you have a 16Bit TCM module and JB131 pins 17 signal and 4 solenoid ground.

 

So, I have the 16 but then..

Does that make the jb131 plug the one right with the jb155? If so, how do I know what numbers are what to check it properly?

I still am unsure of the numbers!

 

JB155 is in the engine bay and plugs into the transmission.
If you are looking a that plug then the black wire on pin 18 is the solenoid grounding wire and the blue wire on pin 13 is the 2/4 brake signal wire.

The plugs I was referring to earlier (for 16Bit and 32Bit modlues) are located on the TCM (Transmission control module) which lives in the cabin, behind the kick panel of the left front footwell (A pillar).
Might be easier to do you measurements there.

 

Thanks for the reply!

I have a code p0778. I need to diagnose it and have tried to measure according to the jtis, 2/4 brake duty (code p0778)

I have followed the steps but get stumped when I have to go to the jb131 plug to test. (Attached in photo)



Can you explain the steps p3 & p4? I don’t know how I would measure those values with the transmission plug and the plug jb131 (you mean that is on the TCM itself? Or am I missing something?)

I just want to be able to complete the steps to diagnose my gearbox fault properly

 

JB155 is the connector that goes into the transmission itself...to the solenoids, speeds sensors and temp sensor.
Whereas JB131 is the other end of the wiring harness that goes into the transmission control module - the electronic computer that instructs the transmission what to do.

What they are asking you to do with these steps P3 and P4 is to check the continuity of the specific wires between between those two plugs, effectively trying to establish if one of both wires are open or high resistance.

The issue you may have is getting your relatively short multi-meter leads to be reaching both plugs at the same time.....so you might need a test wire to extend from one of your meter probes to reach one plug while the other probe can reach the other plug more easily.
If you have difficulty getting your meter probes to make contact with the plug contact, you can use a sewing pin to insert through the back of the plug (following alongside the wire in the back of the plug) to enable you to get a contact with the plug more readily.

 

Glad I asked a more specific answer. Many thanks for the clarification it means worlds. Thanks to you and the fine people on this forum for all the help you guys give!