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Effective Use of GM electronic Service Information Part 2
Posted to Technical Tips Forum on 7/28/2015 5 Replies

Part 2.

In Part 1, we took a brief look at some of the changes or enhancements to GM electronic Service Information (eSI) or "SI" for short. Leaving off at a basic introduction of the CGI Viewer was a good break point to allow focus here in Part 2 on understanding how the viewer can be very useful.

I will use a specific example of a search where one might be slightly challenged to locate all of the appropriate information. The example is taken direct from an activity that I created and use in class when instructing the use of SI during electrical diagnosis.

The scenario is this as follows and the path followed through diagnosis may not necessarily be the most proficient route. However, for better or worse, it was the one taken by the students involved.

A repair order was created for our program 2014 Chevrolet Cruze diesel, which has "recently returned from the body shop after accident repairs to the right front of the vehicle". (Staged scenario)

The concern is described as, "The right front headlamp does not work".

For the benefit of students learning procedures and corporate protocol, they are reminded to follow a path of documentation as they would be expected to complete in a normal warranty scenario, time punches documentation and all. That however, is not the focus here.

The obvious first step is to begin by verifying the customer concern. It's been a while, but I recall that right headlamp and park lamp were confirmed to be not functioning. It isn't really important because the focus of the activity here is solely some benefits of using the CGI Viewer plug-in.

While scanning for DTCs with the ignition on, it was noted that the windshield wipers chatter slowly and erratically across the windshield with the lights turned on.

No bulletins or other useful published information applied and a cursory preliminary check without yanking too hard on electrical harnesses and connectors revealed nothing obvious.

There's always a fine balance between a reasonable inspection and causing or fixing an intermittent. I tend to advise a hands-off, inspect only approach at the start, so as not to disturb an intermittent condition and restore temporary operation. While a thorough inspection might unearth the problem in this case, that isn't the focus.

From the Diagnostic Starting Point and Diagnostic System Check-Vehicle documents, a sense of direction and associated diagnostic documents were located.

With GDS2 and MDI connected, there was an associated current DTC with the non-functioning lamp and the lamp could not be commanded on.

The obvious "gut feeling" for those familiar with electrical diagnosis and some but not all of my students are, is that the system was back feeding due to a grounding issue or similar.

Where diagnosis gets interesting and involving, is locating the appropriate schematics.

Since the concern was lighting system related, the path taken beyond building the vehicle and entering the Service Manual/Bulletins page followed through Body Systems > Lighting > Headlamps > Exterior Lights Schematics and Routing Systems DRL, or possibly Park Lamps.

There's a couple of options that can be taken, to verify appropriate fuses as would be a preliminary step and quickly review any commonality on the power and ground side of the affected circuits. Nothing was apparently common to both systems from the fused side.

When looking at individual documents, it is time-consuming comparing multiple schematics, so to get a better view of the involved circuits, the following path was taken from the "Service Category" menu: Power and Signal Distribution > Wiring Systems and Power Management > Schematic and Routing Diagrams > Ground Distribution Schematics > Figure 2: G103, G104 and G105.

Selecting the G104 group document, puts all G104 grounded circuits on the same "map" alleviating the need to use multiple documents.

Since GM vehicle electrical system zoning identifies that # 100 circuits are in the under hood electrical zone, reviewing the routing diagram identified G104 as being located in the right front of the compartment, close to the engine mount area. The students verified it as being securely connected, performed a voltage drop at the location with the lights on and found nothing out of specification to suspect and issue with the connection.

At this point, it was an opportune moment to reinforce the benefit of the CGI viewer. When mousing over or hovering over specific areas on many of the more current vehicle platform schematics, the conductor paths will highlight in red, showing the entire path, much like Jorge Menchu's highly regarded and practiced colouring with crayons exercise. In the case of G104, you will see from the following two photos that not all of the conductors connected to G104 highlight together. [Hover 1]

Approximately half of the wires connected to the G104 location remain in black while some are in red. Moving the mouse to hover over a conductor that remained black, now reverses the colours as you can see here [Hover 2]

This immediately identifies that there are more than one terminated ground bundle at the G104 location. With the students now clued in, they rechecked the ground stud and discovered only one bundle and ring terminal fastened to the stud.

Searching a little deeper along the wiring harness, they discovered another branch with ring terminal that should have been connected to the stud.

You will recall that the vehicle had "returned from the body shop". The problem was simply that only one ground bundle had been reconnected once the inner panel had been refinished!

In reality, the activity was staged by yours truly to replicate what does occur in the real world and has happened to me, all be it on a different vehicle sent to me from the body shop.

The other benefit of the CGI viewer, was the aforementioned bonus when mousing over components, that results in single or multiple hand symbols, signifying that there are one or more links at these "hot spot" locations.

You will recall that previous to the adoption of the CGI viewer, the "LOC" or "DESC" buttons had linked to the Master Electrical Component list, where the desired component or connector end view had to be searched either by component name or code, depending on the time line in SI.

With a mouse click on the component hot spot in the schematic, followed by a second mouse click to select a desired harness routing view or connector end view from the drop down menu that opens, the desired information is immediately linked to directly from the schematic. [Mouse Over]

While there are many ways to locate information within GM eSI, when time is of the essence, (think 0.0 hr - 0.3 hr) navigation proficiency is important.

There are numerous tips, tricks and methods to use GM SI efficiently in our work and they depend heavily on vehicle platform along with stage of SI development at that time. We can only touch on a handful here, but hopefully there's a useful tip or two for you to try next time.


Martin from British Columbia

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