TRNW-2: 6t40 can bus diagnosing

[Dan Hogan]

Here's a possible HSCAN network schematic for a 14 cruze 1.4

[cid:33472623-a78d-48bc-b724-4f055c5311a3]

The HSCAN bus is terminated internally by the BCM on one end and the ECM on the other.  Highlighted in yellow.

If you're reading 60 ohms at the DLC, one end of the bus is no longer terminated somewhere and I think you've found at least the likely end ---> ECM.  Remember the MF3/MZ0 wiring is not present in your application.  Ignore.

Battery negative disconnected.  No power to vehicle prior to test.

I think the fastest way to verify the bus wiring between the TCM and ECM would be to disconnect the TECHM connector, ECM connected normally and measure the resistance between pins 7 and 8 on X1.  If intact, this should be 120 ohms.  This would test the wiring and ecm termination.  You can also measure the bus going back to the BCM / DLC by measuring at pins 6 and 14 here at the TECHM, this should also be 120 ohms.   While the TECHM connector is disconnected, good time to check terminals for pin fit or whether they look expanded or damaged.  Loose terminal fit can be real pain to diagnose.

[cid:cf8743f0-a5c3-4fcc-b53b-b30dc1721944]




---


Dan Hogan

Buster's Transmission Service

https://busterstransmission.com

704.847.5321

________________________________
From: trnw2-bounces at trnw.net <trnw2-bounces at trnw.net> on behalf of Justin Merritt via trnw2 <trnw2 at trnw.net>
Sent: Sunday, October 19, 2025 1:34 PM
To: trnw2 at trnw.net <trnw2 at trnw.net>
Subject: TRNW-2: 6t40 can bus diagnosing

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

[cid:2bcc003d-9b28-430c-a726-8969535e3274 at namprd17.prod.outlook.com]

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