1. automotive and vehicles
2. electric vehicles

Mid-Mid-May 2015, Volume 17, No. 10
Service
Information
Circuit/
System
Verification
Changes
Based on feedback from GM field service engineers, the Technical Assistance ­Center
(TAC), GM service trainers and dealership service technicians, there have been a
few cases documenting the difficulty of isolating an issue using the diagnostic procedure Circuit/System Testing category in the Service Information. In most cases, the
Circuit/System Verification was not performed. If the verification procedures were
performed prior to the circuit testing, the correct issue would have been found and
­corrected.
CONTENTS
Circuit/System Verification Changes . . . . . . 1
The Beginnings of a New Bulletin . . . . . . . . . 2
For example, Circuit/System
­Verification refers to diagnosing a
5V reference DTC P0641 before
the sensor DTC.
Mobile Device Wireless
Charging Update. . . . . . . . . . . . . . . . . . . . . . 3
As a result of these reports
on testing and verification, the
­Diagnostic Procedure Instructions
(linked at the top of any diagnostic
procedure in the Service Information) have been modified.
Damaged Suspension Components
Due to Vehicle Modifications. . . . . . . . . . . . . 4
Safety Alert Seat Cushion Discomfort . . . . . 3
Comfort Open/Remote Venting Windows . . 5
Duramax Diesel Head Gasket
Replacement. . . . . . . . . . . . . . . . . . . . . . . . . 6
Determining a Current
Condition
Originally, the Diagnostic Procedure Instructions did not instruct
Unseated Pins in the Transmission
Connector. . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Diagnostic procedure instructions link in the diagnostic
procedures
continued on page 2
Customer Care and Aftersales
Service Information Circuit/System Verification Changes
continued from page 1
a technician to perform any of the three diagnostic categories
— Circuit/System Verification, Circuit/System Testing, and
­Component Testing — in a specified order. However, performing
the procedures in the Circuit/System Verification category first
aids in determining if a vehicle condition is current.
The Service Information has been changed to reflect this. The
Diagnostic Procedure Instructions explain that, when supported,
Circuit/System Verification needs to be performed prior to the
Circuit/System Testing. The verification procedures will determine
the following conditions:
• If a higher priority concern needs to be addressed first (e.g.,
other DTCs)
• If other conditions are present (e.g., low fluid level)
• If the condition is current
• If the condition is intermittent
• If the system is all OK
Repair
Verification
ew Contact
Us button
Other changes regarding the Circuit/System Verification include
modifications to the Diagnostic Repair Verification information.
The link to the Diagnostic Repair Verification is in the Repair
­Information category.
Diagnostic Repair Verification link in the Repair Information category
Step 7 now includes the additional information:
7.Perform the Circuit/System Verification and verify the result
ends with an All OK.
It is recommended to perform the Circuit/System Verification to
validate a proper repair has been made.
Thanks to Andreas Mueller, David Miller and David Nowak
The Beginnings of a New Bulletin
Things change fast in the automotive world. Products and components may require repairs that need to be made immediately
or service procedures need to be updated. So how are these
conditions found? And how does the word get out to dealerships?
There are many ways General Motors communicates with
­dealership technicians about diagnostic repairs and other
­information that are not included in a standard Service Information (SI) document. One method is for the Technical Assistance
Center (TAC) or the Brand Quality group to publish a PI
(Preliminary Information)/Bulletin.
Find the Cause
The first step is for TAC or the Brand Quality group to identify
the need for this type of service communication, which is done
by monitoring various sources, including Field Product Reports
and Product Information Reports (Canada), TAC cases, field
service engineers’ reports, dealer calls, and the product action
centers.
Once the need is identified, it is necessary to gather all of the
concern, cause, and correction information. For some conditions,
this is very easy and self-explanatory. In other cases, it is necessary for TAC and/or the Brand Quality Manager to work with
engineering, field service engineers, Service Learning Center
technicians, and/or local dealerships to gather all the necessary
information.
Write the Repair
After all concern, cause, and correction information is gathered,
a Brand Quality bulletin team author or TAC escalation team
2
author creates a draft outlining the condition and correction. In some
cases, existing repair procedures and labor operations found in the
Service Information are utilized for standard repairs and diagnosis.
Other times, everything may be available but it may be necessary
to obtain photos of components or repairs on the vehicle. Photos or
other documentation may be obtained from GM fleet vehicles, local
dealerships, engineering, or field service engineers.
If a complete repair procedure has to be created, a Brand Quality
bulletin author will work with the Brand Quality Manager and an onsite Service Learning Center technician to document the diagnostic/
repair steps, take photos, determine what parts are needed, and
develop a labor time.
Stock Parts
In the event that parts are going to be required, a “service part alert”
is created to ensure that Customer Care & Aftersales (CCA) has
­appropriate parts stock available for dealerships to order before the
PI/bulletin is released in an effort to prevent a back-order situation.
Once the draft is complete, the final draft is created and reviewed
before being published in the Service Information. Depending on
the topic, many PI/bulletins are forwarded to be published as a
GM TechLink article and also considered as topics for the monthly
Emerging Issues broadcast (U.S.) or TAC Talk broadcast (Canada).
There are some instances where a Global Connect message is sent
to dealerships to call additional attention to a recently released
PI/bulletin — particularly when a repair was not available when the
PI/bulletin was initially published.
Thanks to Jamie Parkhurst
Mid-May 2015
Mobile Device Wireless Charging Update
The Wireless Charging system for smartphones is an inductively coupled means for
wirelessly charging mobile devices in the
vehicle; no cables necessary.
It’s available on 2015-2016 ATS, CTS
sedan, Tahoe, Suburban, Yukon models,
and Escalade models. It will be offered on
additional models for the 2016 model year.
(WPC) Qi Standard, meaning that it
is equipped with a PMA or Qi wireless
charge “receiver” that will work with the
charge “transmitter” installed in the vehicle. A device may use built-in charging
circuitry or an adapter (external plug-in device which contains the charging circuitry).
Charging a Device
1.To charge a device, with the vehicle
­ignition on, place the device, face up, on
the charging symbol on the charging mat
(all other objects should be removed
from the charging surface).
2.Adjust the position of the device slowly
until the battery charging symbol displays on the infotainment touch screen,
indicating the device is charging.
On ATS and CTS sedan, the wireless
charging system is located in the hidden
storage compartment behind the climate
control panel below the Cadillac CUE
screen. On the full-size SUVs, the system
is located on the top of the center console
armrest.
An increasing number of smartphones
have built-in wireless charging technology. Some smartphones require a wireless
capable back cover or adapter. Customers should contact their phone retailer
for information about a wireless charging
adapter/back cover if it’s required for their
phone.
A compatible device is one that is compliant with the Power Matters Alliance
(PMA) or Wireless Power Consortium’s
TIP: If the device does not charge, verify it is properly positioned on the charging
surface. It may be necessary to rotate it
180 degrees to help establish a connection. Do not slide the device. Pick it up and
wait three seconds before repositioning
it. Also, the use of a protective case may
require more precise placement or may inhibit charging. Try removing the case.
There is a charging coil located in the
center of the charging surface and the
mobile device has a charging coil typically
near the center of the device. These coils
must be lined up in order for charging to
proceed.
When the Interruptible Retained Accessory Power (IRAP) relay is closed (when
the vehicle ignition is in Run or Accessory
position), the system is able to detect the
device, establish communications with the
device to confirm it is a compatible device,
and then deliver charging power to the device via the wireless interface.
If a non-compatible device or metallic foreign object is detected, the system will not
transfer power. The charger monitors its
internal temperature and will shut down if
the charger temperature exceeds 185° F
(85°C).
The BCM will detect the device battery is
charging and send a serial data message
to the infotainment touch screen, which
will indicate a device is currently charging. When the indicator is toggling on and
off, it indicates a thermal limit has been
reached and the device will not charge.
It is normal for the phone temperature to
­increase during the charging process.
Charging also may be interrupted while
driving over rough conditions. Reposition
the mobile device to continue charging.
TIP: For any Wireless Charging system
concerns, refer to circuit/system verification and testing in the appropriate Service
Information. A scan tool cannot be used
since the system is not connected to any
control module. No DTCs or data parameters are available.
Compatible Devices
For the latest information about mobile
­device compatibility with the Wireless
Charging system, go to the owner center
for the appropriate model: my.chevrolet.
com/learn; my.gmc.com/learn; my.buick.
com/learn; or my.cadillac.com/learn.
A PDF of Wireless Charging compatible devices can be downloaded from the
­website.
Thanks to Hassan Abdallah
Safety Alert Seat Cushion Discomfort
When sitting in the driver’s seat
on some 2015 Escalade models,
Silverado, Suburban, Tahoe,
Sierra, Yukon Models; 2014
Silverado 1500 and Sierra 1500
models equipped with the Driver
Alert Package (RPO Y65), it may
be possible to feel the left or right
haptic seat motor.
The haptic seat motors are located in the seat cushion. The
haptic seat motors also are called
front seat lane departure warning
actuators.
Haptic seat motors in the seat
cushion
The orientation of the haptic seat motor can be changed to help
reduce seat discomfort.
Mid-May 2015
Access both haptic
seat motors and rotate the motors flat.
Reinstall them into
the seat cushion.
The different orientation of the motors
will help improve the
comfort of the seat
cushion. Do not attempt to modify positioning of the motors
beyond the rotation
shown.
Rotate the haptic seat motors flat.
Thanks to
Jim Will
3
Damaged Suspension Components Due to Vehicle
Modifications
There may be some various handling or vehicle dynamics concerns,
noises from the suspension or underbody, or issues related to damaged suspension components on some 2007-2013 Escalade EXT,
Avalanche; 2007-2015 Escalade models, Silverado, Suburban,
Tahoe, Sierra models and Yukon models.
These concerns may occur if the vehicle’s suspension system has
been modified by using suspension lift or lowering kits, or making
modifications to the vehicle, including adjusting components beyond
factory specifications. Examples of these modifications include, but
are not limited to, adjusting torsion bar suspensions to change suspension height and/or aftermarket wheels and/or tires installed.
TIP: Before any in-depth diagnostics are performed, technicians
should be aware that various issues may occur if the vehicle has
been modified. Inform the customer the conditions noted may not be
covered under the terms of the New Vehicle Limited Warranty.
Most of the larger lift kits are easy to identify because of the major
modifications made as compared to a stock vehicle.
Following are some components to inspect to help identify some of
the smaller changes that can still cause handling or noise concerns.
If there is any question regarding potential modifications, compare
the vehicle to a like vehicle and look for modified components.
Here are some examples of installed aftermarket suspension components:
Aftermarket Lift Kit Block (1)
Aftermarket Lift Kit Blocks Removed (2)
Aftermarket Coil Spring Spacer (3)
Aftermarket Lift Kit Blocks Installed (4)
Aftermarket Coil Spring Spacer (5)
Aftermarket Rear Leaf Spring Lift Block (6)
continued on page 5
4
Mid-May 2015
Damaged Suspension Components Due to Vehicle
Modifications
continued from page 4
Improperly Adjusted Torsion Bars (7)
Quality Control Marks (8)
Inspect for improperly adjusted torsion bars, resulting
in improper Z-height adjustments. In this example, the
Z-height for this truck would be above the specifications but there is not an actual lift kit installed.
When determining if a vehicle has been modified, additional clues
can be found by inspecting for quality control marks from the factory
that are not aligned (especially on new trucks). The green quality
control marks do not line up, indicating there has been tampering
with this vehicle.
Improperly Adjusted Z-Height
The following example shows lift
provided by improperly adjusting the
Z-height. In this example, the front
suspension has been raised about
three inches.
Thanks to Jim Will
Comfort Open/Remote Venting Windows
On some 2013-2014 XTS and 2014 CTS Sedan (VIN A) models, the windows may roll
down when this operation is not desired after using the Remote Keyless Entry (RKE)
transmitter (key fob). Some owners may have found all windows were down when
­returning to their vehicle.
These models may be equipped with the comfort open or remote venting window feature, which enables users to lower the windows from outside the vehicle by pressing and
holding the Unlock button on the RKE transmitter. The Unlock button must be held long
enough for the windows to start lowering to the full open position. Pressing the Unlock
button again will cause the window movement to stop.
The comfort open/remote venting windows can be turned off if requested by the owner.
This should only be done if the owner requests the feature be turned off.
On CTS Sedan (VIN A) models, contact the Techline Customer Support Center to
­obtain a VCI number to disable this feature.
For XTS models, reprogram the BCM. The selection option to disable this feature is
found in the “Locking" section.
Thanks to David Antal
Mid-May 2015
Press and hold the Unlock button to lower the windows.
5
Duramax Diesel Head Gasket
Replacement
GM TechLink is published for all
GM retail technicians and service
consultants to provide timely
information to help increase know­
ledge about GM products and
improve the performance of the
service department.
Publisher:
John Meade
GM Customer Care and Aftersales
Editor:
Lisa G. Scott
GM Customer Care and Aftersales
Technical Editor:
Mark Spencer
/ [email protected]
Production Manager:
Marie Meredith
Graphic Design:
5by5 Design LLC
/ [email protected]
Fax number:
3 1-248-729-4704
Write to:
* TechLink
PO Box 500
Troy, MI 48007-0500
GM TechLink on the Web:
The following are recommendations and
best practices to follow during Duramax
­diesel cylinder head service or gasket
replacement on 2001-2015 Express, Silverado, Savana and Sierra models equipped
with the Duramax diesel engine (RPO LB7,
LBZ, LGH, LLY, LML, LMM).
Gaskets are Not Interchangeable
The left
and right
cylinder
head gaskets are
not interchangeable.
Improper
placement
of the cylinder head
gasket will block coolant and oil passages.
Blocked coolant and oil passages will cause
severe engine damage.
Surface Cleaning Procedures
Do not use any power type sanding devices.
Do not use a wire brush or wheel to clean
gasket surfaces. Do not use chemical cleaning agents on gasket surfaces. Refer to Bulletin #00-06-01-012 for more information.
Refer to Service Information and Bulletin
#06-06-01-006 for engine block and cylinder head sealing surface cleaning procedures.
: GM GlobalConnect
Cylinder Head Bolts
General Motors service tips are intended
for use by professional ­technicians, not
a “do-it-yourselfer.” T­hey are written to
inform those ­technicians of conditions
that may occur on some vehicles, or to
provide­information that could assist in
the proper service of a vehicle. Properly
trained technicians have the equipment,
tools, safety instructions and know-how
to do a job properly and safely. If a
condition is described, do not assume
that the information applies to your
vehicle or that your vehicle will have that
condition. See a General Motors dealer
servicing your brand of General Motors
vehicle for information on whether your
vehicle may benefit from the information.
Inclusion in this publication is not
­necessarily an endorsement of the
individual or the company.
During cylinder head servicing or cylinder
head gasket replacement, always use new
Copyright© 2015 General Motors
All rights reserved.
M12 cylinder head bolts. The M8 cylinder
head bolts can be reused.
Clean the bolt threads and holes.
Handling Gaskets
Leave the gaskets in the packaging until
they are ready to be installed on the block.
Once removed from the packaging, handle
them with great care.
Do not set the gaskets on workbenches or
toolboxes to avoid possible introduction of
foreign debris.
Do not use air to blow between the gasket
layers.
Cylinder Head Surface
Do not machine the cylinder head surface.
Measure the cylinder head for warpage with
a straight edge and a feeler gauge. A cylinder head block deck with warpage in excess
of 0.1 mm (0.0039 in.) must be replaced.
Installation
It is recommended to install two head bolts,
secured to minimal torque (20 Nm), prior to
installing the remaining head bolts. This will
minimize the chance of introducing other
foreign material during installation.
Use a paint pen on the M12 cylinder head
bolts during installation to mark the head of
each bolt, one by one, indicating which of
the four torque steps have been completed
on that particular bolt. This prevents skipping a step or doing a step twice. In the
end, all bolts should have four paint pen
marks.
Thanks to John Stempnik
Unseated Pins in the Transmission
Connector
On some 2006-2011 STS; 2007-2009 SRX;
2008-2014 CTS (VIN D) built prior to May
1, 2014; 2013-2014 ATS built prior to May
1, 2014; and 2014 CTS Sedan (VIN A)
built prior to May 1, 2014, equipped with a
6-speed automatic transmission, there may
be one or more of the following conditions:
• Service Engine Soon lamp illuminated
• Reduced power
• Engine will not crank over, no start
• Multiple warning lamps illuminated
• Transmission shifts hard
• Door locks cycle while driving
municate with the scan tool. The following
DTCs may be set: C0242, C0561, P0575,
P0615, P0700, P0856, P1629, P2544,
U0073, U0074, U0100, U0101, U0109,
U0121, U0140, U2100, U2105, and U2106.
These conditions may be caused by an unseated pin(s) in the transmission connector.
Inspect the transmission connector X1 terminal connections. Disconnect the connector and carefully tug on each wire to ensure
the pins are fully seated. A side load on the
wires may cause a false positive lock. Repair
the connections as necessary.
Thanks to David Roat
The Transmission Control Module (TCM) or
Engine Control Module (ECM) may not com6
Mid-May 2015