TRNW-2: 6t40 can bus diagnosing

[Chris and Cathy Kershaw]

Mf3/mz0 lines are showing wires for vehicles with those rpo codes. Since
mh8/mh9 shows a techm id say that’s how your vehicle is setup.

 A vin would be helpful on something like this.

The continuity situation you’re describing seems impossible to me. You
describe having continuity through the tcm but not to the tcm.

I’d back up a few steps, what modules communicate with a scan tool?

 Don’t just do a full vehicle code scan but go to each one and attempt to
view data. Often a no comm module will just show no codes on a full vehicle
code scan.

What modules set communication codes and what are those codes?

On Sun, Oct 19, 2025 at 1:35 PM Justin Merritt via trnw2 <trnw2 at trnw.net>
wrote:

> Hello all,
> I am working on a 14 Chevy Cruze 1.8 engine. I am chasing a loss of
> communication of both the transmission and engine control module. I
> struggle when it comes to testing wiring on the can bus lines, I just don’t
> have enough experience with it. I’m determine to figure this one of for a
> learning experience. I have included a diagram of some wiring I am testing,
> and I have continuity between pin 29 and 6 and 43 and 14, but I do not have
> continuity between 29 and 7 and 43 and 8. The diagram cuts off, but the
> mf3/mz0 squares just loop around the tcm and back into the wires 6 and 8 of
> the tcm.  Would I be thinking right that I have a break in the 2 bus wires
> 29 and 7, and 43 and 8 that is causing my no communication?
> Thanks for any help.
> Justin
>
>
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