SB-10043829-6448
File in Section:

Service Bulletin

Bulletin No.:
Date:

07 - Transmission/Transaxle
08-07-30-021G
March, 2012

TECHNICAL
Subject:

Loss of High Speed GMLAN Communications, Intermittent No Crank, IP Gage
Fluctuation, Intermittent Door Lock Cycling, Intermittent Chime Operation, Various IP
Warning Lamps Illuminated, Transmission May Not Shift, Communication DTCs U0073,
U0100, U0101, U0102, U0109, U0121 or U0140 Set (Repair Terminals in Transmission
Harness Connector, Repair Open or Shorted GM High Speed LAN Circuits, Open or
Shorted Data Link Resistor, Corrosion or Poor Connections in Various Control Module
Connectors)

Models:

2007–2010 Cadillac XLR
2007–2012 Cadillac Escalade Models
2009–2012 Cadillac Escalade Hybrid
2007–2012 Chevrolet Avalanche, Corvette, Silverado, Suburban, Tahoe
2008–2012 Chevrolet Silverado Hybrid, Tahoe Hybrid
2007–2012 GMC Sierra, Yukon Models
2008–2012 GMC Sierra Hybrid, Yukon Hybrid
2008–2009 HUMMER H2
Equipped With Gasoline Engine and 6 Speed Automatic Transmission 6L80 (RPO MYC)
or 6L90 (RPO MYD)
Equipped With Hybrid Propulsion (RPO HP2) and Two Mode 2ML70 Automatic
Transmission
This bulletin is being revised to add the 2012 model year and additional Correction
information. Please discard Corporate Bulletin Number 08-07-30-021F
(Section 07 – Transmission/Transaxle).

Condition
Some customers may comment on any of the following
conditions:
• The malfunction indicator lamp (MIL) may be
illuminated.
• Instrument panel cluster (IPC) warning lamps may
illuminate.
• The transmission may not shift or defaults to
2nd gear.
• The door locks may cycle by themselves.
• The engine may not crank intermittently.
• A driver information center (DIC) message may be
displayed.
• The IPC gages may fluctuate.
• Applying the brakes may cause the IPC to
become erratic and the chimes to operate
simultaneously.

Copyright 2012 General Motors LLC. All Rights Reserved.

Depending on the vehicle and build, technicians may
find one or more, but not limited to the following, High
Speed GMLAN Communication DTCs set as Current or
History:
• P0700: Transmission Control Module (TCM)
Requested MIL Illumination.
• U0073: Control Module Communications
Bus OFF.
• U0100: Lost Communication With ECM/PCM.
• U0101: Lost Communication With Transmission
Control Module (TCM).
• U0102: Lost Communication with Transfer Case
Control Module (TCCM).
• U0109: Lost Communication With Fuel Pump
Control Module.
• U0121: Lost Communication With ABS Control
Module.
• U0140: Lost Communication With Body Control
Module (BCM).
• U186B: Lost Communication With TCM.

Page 2
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•
•
•
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•

March, 2012

U0129 : Lost Communication with Brake System
Control Module.
U186B: Lost Communication with TCM.
U0293: Lost Communication with HP2 Powertrain
Control Module.
U1862: Battery Energy Control Module Lost
Communication with Communications Gateway
Module.
U1886: Battery Energy Control Module Lost
Communication with Engine Control
Module (ECM).
U1888: Hybrid Powertrain Control Module Lost
Communication With Starter/Generator Control
Module.

Cause
These conditions may be caused by, but not limited to,
any of the following:
• Chafed, damaged, pinched, open or shorted
wiring.
• The terminal(s) for the High Speed GMLAN Serial
Data Bus has or have backed out of the 16-way
electrical connector to the automatic transmission.
• The terminal position assurance (TPA) lock in the
transmission 16-way electrical connector is not
fully seated.
• The High Speed GMLAN Serial Data Bus circuits
are open or shorted to ground.
• Corrosion in a control module connector.
• Intermittent or poor connections in the inline
connectors containing the High Speed GMLAN
Serial Data Bus circuits.
• Water intrusion in a control module connector.
Note: Model Year 2007 vehicles.
• The Terminator Resistor is open or shorted.
Note: Model Year 2008 Sierra and Silverado vehicles.
• The Data Link Resistor is open or shorted.
Note: Model Year 2009 and newer Sierra and
Silverado vehicles.
• The Data Link Resistor 1 is open or shorted.
Note: Model Year 2008 and newer Avalanche,
Escalade, Tahoe, Yukon vehicles.
• The Data Link Resistor 1 is open or shorted.
Note: Model Year 2008 and newer Hybrid RPO HP2
vehicles.
•

The Data Link Resistor 2 (RPO HP2) is open or
shorted.
Note: The following cause only pertains to hybrid
RPO HP2 vehicles equipped with OnStar® Delete
RPO UE0.
•

The High Speed GMLAN jumper harness loop
connector that plugs into the bottom rear of the
interior driver side junction block, is open or
shorted from chafing on the IP brace.

Bulletin No.: 08-07-30-021G

Correction
Do This

Don't Do This

Repair or replace any
backed out or damaged
transmission connector
terminal(s) as necessary.
Ensure that the transmission
connector TPA is fully
seated (TPA is centered in
check window).
Repair the High Speed
GMLAN Serial Data Bus
circuits that are open,
shorted to ground or have
poor connections.
Repair the corrosion or
water intrusion condition in
the affected module
connector.
Replace the Terminator
Resistor that is open or
shorted.

DO NOT replace any control
module, wiring harness or
component until you have
first isolated the cause of the
condition or followed this
procedure in its entirety.

Replace the Data Link
Resistor 1 or Data Link
Resistor 2 (RPO HP2
vehicles only) that is open or
shorted.
Repair the junction block
jumper harness loop
connector wiring that is open
or shorted. (RPO HP2
Vehicles equipped with
OnStar® Delete
RPO UE0 Only).

Information for the Procedures to
Diagnose and Repair the Above
Conditions
1. Perform the Diagnostic System Check-Vehicle
to begin your diagnosis.
2. Perform a thorough visual inspection of the
vehicle.
3. Depending on the vehicle and vehicle build,
some of the procedures may not be applicable.
4. The following procedure is the only one
applicable to the Corvette and XLR.

Chafed Wiring Harness at Transmission
Case Retaining Clip and Inspection of
the 16-way Electrical Connector for
Backed Out Terminals
1. Turn OFF the ignition and all accessories.
2. Raise and support the vehicle. Refer to Lifting and
Jacking the Vehicle in SI.

Bulletin No.: 08-07-30-021G

March, 2012

2043302

Page 3

2807959

5. Before disconnecting the 16-way connector,
inspect for any backed out terminals (1) as shown.
Fully seated terminals (2,3) are shown for
comparison.
5.1. If a backed out terminal (1) is found, identify
the terminal(s) on the repair order.
5.2. Look at the connector in order to identify the
number of the cavity with the backed out
terminal. Refer to Wiring Systems and Power
Management > Component Locator > Master
Electrical Component List in SI.

2043303

3. Locate the 16-way electrical connector on the right
side of the automatic transmission as shown.
4. Inspect for chafed, damaged, pinched, open or
shorted wiring within the conduit of the harness
where it is secured at the transmission by a metal
attachment clip as shown. Inspect any wiring
harness where these metal attachment clips are
used on the vehicle as needed.
⇒ If the wiring is damaged, repair as needed.
Refer to Power and Signal Distribution > Wiring
Systems and Power Management > Diagnostic
Information and Procedures in SI. Protect the
conduit by covering any sharp edge with butyl
tape and the conduit and wiring harness with
woven polyester (PET) electrical tape. Secure
the harness as needed.

1921876

Note: For 2ML70 Only: Disconnect the 4WAL
electrical connector.

Page 4

March, 2012

6. Use the following procedure to disconnect the
16-way electrical connector:
6.1. Release and hold the slide lock on the wiring
harness connector.
6.2. Rotate the connector lever and remove the
connector from the component.

Bulletin No.: 08-07-30-021G

8. Repair or replace the terminal(s) as necessary
using the following procedure:

1921872

2807963

7. Inspect for any backed out terminals (3) as shown.
Fully seated terminals (1,2) are shown for
comparison.
7.1. If a backed out terminal (3) is found, identify
the terminal(s) on the repair order.
7.2. Look at the connector in order to identify the
number of the cavity with the backed out
terminal. Refer to Wiring Systems and Power
Management > Component Locator > Master
Electrical Component List in SI.

8.1. Locate the terminal position assurance (TPA)
as shown.
Note: The TPA cannot be removed from the connector
while there are terminals present in the connector body.

1921873

8.2. Use a small flat blade tool to push the TPA
until it bottoms out.

Bulletin No.: 08-07-30-021G

March, 2012

Page 5

13. Prior to installing the transmission connector,
perform the following steps to ensure that the TPA
lock is fully seated.

1921843

8.3. See the release tool cross reference in the
Reference Guide of the J-38125 to ensure
that the correct release tool is used. Use the
J-38125-28 tool to release the terminals by
inserting the tool into the terminal cavity as
shown.
8.4. While holding the removal tool in place,
gently pull the wire out of the back of the
connector.
Note: If the female terminal(s) must be replaced, it is
part number 22124472200. It is located in Yazaki tray
number 12 in the J-38125 Terminal Repair Kit.

2089334

Locate the TPA lock in the reassembled
transmission connector. Refer to the arrow in the
illustration above, which points to a TPA lock. This
one is in an unseated position. Using a small flat
blade tool, push to seat the TPA until it bottoms
out. Verify the TPA is fully seated.

8.5. Repair or replace the terminal(s) as needed.
Refer to the instructions in the J-38125
manual.
9. If the wiring is damaged, repair as needed. Refer to
Power and Signal Distribution > Wiring Systems
and Power Management > Diagnostic Information
and Procedures in SI.
10. Slide the new terminal(s) into the correct cavity at
the back of the connector until it locks in place. The
new terminal(s) should be even with the other
terminal(s).
11. Ensure that each terminal is locked in place by
gently pulling on the wire.
Note: The male terminal(s) cannot be repaired as they
are an integral part of the transmission control
module (TCM).
12. Inspect for bent or misaligned terminal(s) in the
transmission half of the electrical connector.
⇒ If they are bent, use a suitable tool and apply
gentle pressure to straighten them. Indicate on
the repair order the terminal number that
was bent.
⇒ If they are damaged, replace the TCM. Refer to
Control Solenoid Valve and Transmission
Control Module Assembly Replacement in SI.

2089456

• If the TPA is off-center in the check window as
shown, then it is only partially seated. Note the
large gap at the arrow. Reseat the TPA lock and
ensure that it is fully seated.

Page 6

March, 2012

Bulletin No.: 08-07-30-021G

3. Remove the left side fuse block as shown.

2089400

• If the TPA lock is centered in the window as
shown, then it is fully seated. The gaps shown
by the arrows should be even on both sides.
Note: For 2ML70 Only: Connect the 4WAL electrical
connector.
14. Connect the 16-way electrical connector to the
transmission.
15. Lower the vehicle.
16. Clear any DTCs that may be present with a scan
tool and verify the proper operation of the vehicle.

2077437

4. Inspect connector X1 (1) on the back of the fuse
block for a loose connection. Secure the connector
as needed.
5. Install the left side fuse block.
6. Connect the negative battery cable. Refer to
Battery Negative Cable Disconnection and
Connection in SI.
7. Clear any DTCs that may be present with a scan
tool and verify the proper operation of the vehicle.

Inspection of Fuse Block - I/P (Left Side)
for Loose Connector X1

Chafed IP Wiring Harness Near Park
Brake Pedal Assembly

1. Turn OFF the ignition and all accessories.
2. Disconnect the negative battery cable. Refer to
Battery Disconnect Caution and Battery Negative
Cable Disconnection and Connection in SI.

The above condition may cause one or more of the
following fuses to open:
• 60A - MBEC1 (#72) (Underhood)
• 30A - AMP (#40) (Underhood)
• 15A - RDO (#41) (Underhood)
• 10A - IPC (#46) (Underhood)
• 15A - AIR BAG BATT (#51) (Underhood)
• 10A - DSM (Left side of IP)

386487

Bulletin No.: 08-07-30-021G

March, 2012

Page 7

Five areas of potential contact have been identified:

2002647
2002643

•

•

The IP wiring branch to C202 may have been
routed outboard of the junction block (left IP) and
the retaining clip (1) off the branch may not have
been fully seated. Possible point of contact (2).

The IP wiring branch to C202 may not have been
secured into place as the gray retaining clip (1) off
the branch was never seated.

2002648

2002646

•

The IP wiring branch to C202 may have been
pushed up and forward into the park brake
assembly and the retaining clip off the branch may
not have been fully seated. Possible points of
contact (1, 2).

•

The IP harness may be in hard contact with the
top rear edge (1) of the park brake assembly.

Page 8

March, 2012

Bulletin No.: 08-07-30-021G

2002649

2002644

When releasing the park brake pedal, the moving
part (1) at the end of the park brake release cable
may be coming into hard contact with the IP
harness.
If a condition is suspected or found with one of the
circuits running to C1 or C2 of the junction block or to
the inline IP-to-body connector C202 or at any of these
areas of concern then remove the front driver side door
sill plate, driver side body hinge pillar trim panel, left IP
outer trim cover and perform the following steps:
1. Turn OFF the ignition and all accessories.
2. Inspect the IP harness for chafed, damaged,
pinched, open or shorted wiring at the park brake
pedal assembly. Refer to the potential damage
points as shown in the photos - at the side and rear
of the park brake assembly. Be advised that
damage may be covered by electrical tape, or
turned away and hid from view.
3. Engage and release the park brake several times.
Observe the moving part at the end of the park
brake release cable as it may contact and damage
the IP harness. Inspect the IP harness at this
possible contact point. Note that any damage may
be covered by electrical tape and/or hid from view.
⇒ If the wiring is damaged, repair as needed.
Refer to Power and Signal Distribution > Wiring
Systems and Power Management > Diagnostic
Information and Procedures in SI. Protect the
harness by covering any sharp edge with butyl
tape and the harness with woven polyester
(PET) electrical tape.
Engage and release the park brake several
times. Verify the harness is no longer making
contact with any sharp edge or point of the park
brake assembly. If it is still making contact,
route it away from the contact point and secure
it with tie straps.
Proceed to Step 4.

4. Inspect how the IP branch to C202 is routed. Route