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