NHTSA ID Number: 10187760
Manufacturer Communication Number: 20NA198
TSB/Document Date: 2021-03-01
Summary
This technical bulletin provides repair information to correct a customer concern of seeing the trailer running lights shut off due to excessive load on the running lamp circuit.
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TSB/Document ID: 20NA198
Replacement Service Bulletin Number:
MFR Communication Date: 2021-01-29
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: EXTERIOR LIGHTING
MFR Component System:
MFR Component Subsystem:
Previous TSB | Next TSB |
Bulletin No.:
Service Bulletin
Date:
20-NA-198
February, 2021
TECHNICAL
Subject:
Brand:
Trailer Running Lights Shut Off Due to Excessive Load on the Running Lamp Circuit
Model:
Silverado 1500
(New Model)
to
2019
2019
2020
2020
2019
2019
2020
2020
Date Breakpoint:
from
Engine:
All
All
to
Silverado 1500
Silverado 2500HD/
3500HD
Sierra 1500
(New Model)
Model Year:
from
Sierra 1500
Sierra 2500HD/
3500HD
Involved Region or Country
North America, Middle East, Argentina (Mercosur), Brazil (Mercosur), Bolivia (West),
Chile (West), Colombia (West), Ecuador (West), Paraguay (West), Peru (West), Uruguay
(West), GM Korea Company, Singapore, Phiippines, Egypt, Other Africa, South Africa.
Additional Options (RPOs)
Equipped with INDICATOR-TRAILER INFORMATION (U1D)
Condition
Some customers may comment that the running lamps may illuminate for a second or
two, and then go out when operating a trailer running lamp circuit with more than 7-8
amps of current draw. On vehicles with LED lighting, the owner may have concerns with a
flash of the lighting about once every 10 seconds.
Cause
The cause of the condition may be that trailers with incandescent running lamps may
have in-rush current that exceeds the trailer lighting module limits for current flow. And
that monitoring voltage may illuminate LED lights even when trailer theft deterrent is not
enabled.
Additional Information
2019 Model Year vehicles, equipped with U1D, use the K68 Trailer Lighting Control
Module to control all trailer lighting through pulse width modulated (PWM) voltage. The
Trailer Lamp Control Module has a current handling capability on the running lamp circuit
of about 9 amps. On a trailer with a large number of incandescent lights, in-rush current
can exceed 20 amps before it settles back to around 8-9 amps. During this inrush or
"marriage" current period, the Trailer Lamp Control Module sees the current as an
"overload" and goes into protection mode.
This was changed for MY 20 to allow 16 amps of continuous current flow by routing the
current through an internal relay in the Trailer Lamp Control Module. 2019 Trucks can be
modified to operate in the same way. If we use 2020 design software and re-pin the
running lamps to pin 25 using the internal relay to operate the running lamps. This
requires a terminated lead to be inserted into cavity 25 on the chassis harness X1
connector. Wiring connected to pin 5 on the X1 will be cut and reconnected to Pin 25.
Terminal in cavity 5 will remain, be blunt cut, and sealed with a closed end duraseal splice
to prevent water entering through pin 5.
For 2019 Model Year vehicles only, software will have to be managed by TCSC. A
record must exist of what trucks have been flashed and that the bulletin has been
completed. Software will not work with the production configuration of wiring. This also
changes the trailer connection detection flashing of LED lighting from every 10 seconds
to every 42 minutes. (Connection detection will still be enabled if trailer theft deterrent is
enabled).
Copyright 2021 General Motors
LLC. All Rights Reserved.
Page 2
February, 2021
Bulletin No.: 20-NA-198
Correction
5652571
For 2019 models ONLY, Follow the steps in the Service Procedure below, and move
circuit 2109 on the Trailer Lamp Control Module from X1 cavity 5 to X1 cavity 25, and load
new software from SPS into the Trailer Lamp Control Module.
For 2020 models ONLY, no wiring changes are required. Only the software update from
SPS to change the monitoring of the trailer lamps from once every 10 seconds to once
every 42 minutes, will have to be completed.
Service Procedure
Important:
• For 2019 models ONLY, the complete
Service Procedure must be completed.
• For 2020 models ONLY, jump ahead to step
#15 and complete the software update, and
reprogramming, only.
1. Raise and support the vehicle. Refer to Lifting and
Jacking the Vehicle in SI.
2. Lower and reposition the spare tire, if necessary.
Bulletin No.: 20-NA-198
February, 2021
Page 3
5209978
3. Locate the Trailer Lamp Control Module (2) and
disconnect the chassis harness X1 electrical
connector.
5652574
5652572
4. Cut off the tie strap retaining the wiring harness
and remove the cover from the connector.
5. Pull the wiring harness out of protective sleeve,
and trim back previous tape to access the wiring.
Page 4
February, 2021
5652575
Bulletin No.: 20-NA-198
5652578
7. Release the 4 tabs on the Terminal Position
Assurance (TPA) and pull slightly upward to
partially release it from the connector housing.
5652576
6. Locate the Gray/Brown wire, at pointer (1),
connected to cavity 5, and cut the wire
approximately 7.62 cm (3.0 in) from the connector
body. The wire will be re-located to cavity 25 (2).
5662018
Bulletin No.: 20-NA-198
February, 2021
5652580
8. Remove the seal from connector cavity 25 and
install the new terminated lead (1) into this cavity.
Ensure the terminal locks into place by pulling back
gently on the wire.
Page 5
5662021
10. Crimp a salmon Duraseal splice sleeve onto the
striped end of the wire stub in cavity 5 of the
connector. Attach the harness side of the grey
brown wire to the end of the terminated lead that
was just installed into cavity 25, using another
salmon duraseal splice sleeve.
5652578
9. Gently press down on the TPA until all 4 tabs
re-engage with the connector and are fully seated.
5662022
11. Use the Ultra torch to shrink the spice sleeve
around the wire and also seal the open end. Use
the Ultra torch to shrink the splice sleeve around
the grey/brown and white terminated lead wires.
Refer to the Weatherpack™ Wiring Repair section
of Wire to Wire Repair. in SI.
Page 6
February, 2021
Bulletin No.: 20-NA-198
Note: For 2020 Model Year vehicles, it will not be
necessary to contact TCSC. Just proceed to reprogram
the Trailer Lighting Control Module to receive the
calibrations. Refer to, K68 Trailer Lighting Control
Module: Programming and Setup, in SI.
15. For 2019 Model Year vehicles, after installation of
the terminated lead, contact TCSC to obtain the
correct software update and reprogram the Trailer
Lamp Control Module. Refer to, K68 Trailer
Lighting Control Module: Programming and Setup,
in SI.
Parts Information
Causal
Part
N/A
5652583
12. Using Woven Polyester (PET) Electrical/
Anti-Abrasive Tape, or equivalent, re-tape the
harness where the previous tape was removed and
reposition the harness back inside the sleeve.
13. Reinstall the connector cover and reconnect the
connector. Replace the tie strap that was removed
previously.
14. Remove the support and lower the vehicle.
Description
Part
Number
Qty
WIRE,SPLICE
(TERMINATED
LEAD)
13575368
1
SPLICE,WIRE
(SALMON)
19300089
2
Warranty Information
For vehicles repaired under the Bumper-to-Bumper
coverage (Canada Base Warranty coverage), use the
following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH)
for coverage information.
Labor Operation
Description
Labor Time
5480858*
Load New Software from SPS, K68 Trailer Lighting Control
Module Reprogramming
0.3 hr.
Add
Move Circuit 2109 on the Trailer Lamp Control Module (2019
Models Only)
0.7 hr
*This is a unique Labor Operation for Bulletin use only.
Version
4
Modified
Released September 28, 2020
Revised October 23, 2020 – Revised Text in Several Procedure Steps to Better Clarify
Repair, Added Graphic, Updated Parts Information
Revised December 04, 2020 – Added 2020 Model Year and Updated Labor Operation
with Add.
Revised January 29, 2021 – Revised Service Procedure to Note it is Necessary to
Contact TCSC For Repair of 2019 Model Year Vehicles Only. It is Not necessary to
Contact TCSC for 2020 Model Year Repairs.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information 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 bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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