GMLAN Diagnostics

Martin from Burnaby Instructor Posted   Latest   Edited  
Discussion
Network Communications
2019 Cadillac XT4 Luxury 2.0L (4 LSY) 9-spd (9T50)

While the DLC drawing in this post relates to a 2019 XT4, the real focus is data communication system changes since ~2017. GM vehicle data communication systems have begun to incorporate Serial Data Gateway Modules (aka Central Gateway Modules) for cyber security, as has been expressed elsewhere.

This may pose some new challenges in the diagnostic approach, not only for technicians who do not regularly utilize information retrieval systems, but also for those who may have learned to diagnose GMLAN systems for vehicle model years prior to 2017.

If you mastered the diagnostic routine easily enough for pre-2017 models, expect to do some reading about the updated electrical architecture, because you will need to revise your diagnostic approach.

Whether it is a 2017 Silverado, XT4 or other new model, be ready for some changes and added diagnostic time over what you may have experienced in the past, even on some vehicles built on the same platform.

Looking at the drawing, can you see the implications of attempting to follow the same old diagnostic practices on GM vehicles, whose data communication systems are now represented by the X84 DLC as shown?

I believe that it would be fair to predict that those who do not incorporate service information into diagnostics until they get stuck, could well be heading down a "rabbit hole" on the new breed.

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David from Philadelphia

 

Diagnostician
 

Martin, is this similar to what the newer Mopars are doing? And should we be anticipating a MDI 3 because of this change?

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Martin from Burnaby

 

Instructor
 

Hi David. My focus is GM only, so am not sure exactly what Mopar and others are doing for cyber security measures.

We heard a rumour quite some time ago about the next gen scan tool interface, but that was all that it was a rumour. Of course, the reality is that just like vehicle design and planning, scan tool interfaces have to be in development early on, to accommodate the next wave of communications technologies. Global B is only just arriving that the MDI 2 was designed for. For most everything GM, the original MDI still works just fine. We use a mix of both.

There will very soon be some notable changes in how the service technician views and accesses some of the GM systems with which we have become familiar over the years.

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David from Philadelphia

 

Diagnostician
 

As far as you know, is the MDI 2 100% backwards compatible with everything OBD2? 

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Martin from Burnaby

 

Instructor
 

It Depends®. There are some GM vehicles with which MDI 1 and MDI 2 do not function well completely. The MDI was designed for use with Global "A" GM vehicles as both the GM approved J2534 programming device and scan tool interface through the original short-lived GDS scan software and the next generation GDS 2.

sandyblogs​.​com/techlink/?p=64…

The Tech 2 was still able to function alongside GDS 2 on through some platforms as late as 2014 MY. 2014 Suburban is a prime example where both GDS 2 and Tech 2 could be utilized and were required in some instances due to certain features missing from GDS 2. Electronic rear suspension calibration was an example where the Tech 2 was required.

Tech2Win was re-developed by Hewlett Packard from the original Tech 2 Emulator software that we used in the classroom environment during the early hand-held Tech 2 training. Tech2Win was designed to function with the MDI, but from the start, had "holes" in it and was not designed for programming. There were many glitches with the software and vehicles which the MDI and Tech2Win combination were not good candidates or properly compatible, were listed in Tis2Web.

So, I would not rely on any MDI to be fully compatible backwards to cover all OBD2 needs as it can be hit and miss.

FWIW, I had an MDI long before we had a Global A vehicle, we were was able to retrieve limited information from some pre-Global A vehicle systems such as transmission data on a 2009 Malibu 2.4L with 6T45 transaxle. This was done by building the vehicle as a Heritage High Roof (HHR) Euro model.

A benefit of the MDI 2 is offline connection to vehicles using Point to Point WiFi . The MDI Manager is used to select and set up wired connection (USB) , WiFi through an access point and lastly, Pont to Point (P2P) WiFi using two small WiFi dongles as received with the MDI 2.

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