Service Bulletin

Bulletin No.: 07-08-42-006U
Date: June, 2025

INFORMATION
Subject:

Information on Available Module Calibrations to Update Bulb Outage Detection
on Vehicles Produced by a Second Stage Manufacturer (Upfitter), Turn Signals
Flash Fast after Factory Box Removed

Models:

2007-2018 Chevrolet Silverado
2019 Chevrolet Silverado LD
2019 Chevrolet Silverado 1500 (New Model)
2019 Chevrolet Silverado 2500/3500
2020-2021 Chevrolet Silverado 1500
2020-2025 Chevrolet Silverado 2500HD/3500HD
2022-2022 Chevrolet Silverado 1500 New (RPO J22, VIN Digit 5 = A / D)
2023-2025 Silverado 1500
2007-2018 GMC Sierra
2019 GMC Sierra Limited
2019 GMC Sierra 1500 (New Model)
2019 GMC Sierra 2500/3500
2020-2021 GMC Sierra 1500
2020-2025 GMC Sierra 2500HD/3500HD
2022-2022 GMC Sierra 1500 New (RPO J22, VIN Digit 5 = H / U)
2023-2025 GMC Sierra 1500

Attention:

This Bulletin also applies to any of the above models that may be Export
from North America vehicles.

This bulletin has been revised to update applicable information within the bulletin.
Please discard Corporate Bulletin Number 07-08-42-006T.
Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws
applicable to the activities it performs under this bulletin, including but not limited to handling, deploying,
preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a
conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you
must follow those applicable laws.
• The information contained in this bulletin only applies to models that could have been ordered with RPO ZW9,
which will be completed by a second stage manufacturer (upfitter) and may need to have the rear turn signal
bulb outage detection capability changed.
Note: Due to higher electrical architecture complexity on MY24+ vehicles, please thoroughly review the Online order
guide for valid ZW9 vehicle combinations. If the ZW9 option is not available for your vehicle combination, please
contact gmupfitter.com for additional information.
Wheel size note: Wheel size of 18" has been approved for use on 2500 series when ZW9 is requested.
• 2014 and earlier 1500 Series trucks only have Option #1 available.

Copyright 2025 General Motors. All Rights Reserved.

Page 2

June, 2025

Bulletin No.: 07-08-42-006U

Production vehicles will be manufactured with one of the following rear turn signal bulb outage detection
software options:
1. A standard production vehicle will have BCM software that checks for two bulbs functioning in each rear turn
signal bulb circuit. If one or more bulbs are inoperative, the BCM will “fast flash” the Instrument Panel Cluster
(IPC) turn signal indicator as required by Federal Motor Vehicle Safety Standard (FMVSS) 108 and Canada
Motor Vehicle Safety Standard (CMVSS) 108.
2. Certain 2500 and 3500 models can be ordered with a new option (RPO 9U5) where the software checks for one
bulb functioning in each rear turn signal bulb circuit. If the bulb goes inoperative, the software will “fast flash” the
Instrument Panel Cluster (IPC) turn signal indicator as required by Federal Motor Vehicle Safety Standard
(FMVSS) 108 and Canada Motor Vehicle Safety Standard (CMVSS) 108.
3. Models built with a pickup box delete or chassis cab option (RPO ZW9) will be produced with a software that
has no turn signal bulb outage detection capability (LED compatible). The IPC turn signal indicator will flash at
the same rate no matter how many turn signal bulbs are inoperative.
Note: For 2015 – 2025 trucks, B3951 & B3950 DTCs for rear tail lamps could set on any truck (ZW9 or E63) if LED
lamps are installed (or lamps are inoperative). This code is used as an assembly verification but does not affect the
function of a properly operating system with LED lights installed.
In some cases, the upfitter may wish to change the turn signal bulb outage detection capability so that the turn
signals work correctly with their upfit or to meet certain requirements. This requires VCI support. VCI numbers can
be requested through Techline Customer Support Center (TCSC) using the applicable method below:
• For US ONLY: VCI support does NOT require a call to TCSC and can be provided by using the Dealer Case
Management (DCM) portal in GlobalConnect. If additional support is needed once the DCM case is created,
contact TCSC at 1-800-828-6860. If calling is required, select "Prompt 1" and then "Prompt 2" for VCI support.
For US only a DCM case is required for phone support
• For Canada: Contact TCSC at 1-800-828-6860 (English) or 1-800-503-3222 (French). Select "Prompt 1" and
then "Prompt 2" for VCI support.
• For all other regions: Contact your regional Technical Assistance team for Global Techline Support.
Note in the DCM case or if calling to advise the TCSC consultant which turn signal bulb outage detection capability
is needed from the following list:
1. Factory standard production TWO bulb outage detection.
2. Optional (RPO 9U5) ONE bulb outage detection.
3. NO bulb outage detection (LED compatible).
Notice: Option 3 is only available on 2015 – 2025 trucks and is included on trucks built with the RPO ZW9
box delete option.

The modules specified by TCSC can then be reprogrammed with the correct software.

Warranty Information
As with any vehicle modifications these changes and expenses (from TCSC, parts, labor, or other expenses) should
not be considered warrantable repairs and should not be charged under warranty. These modifications are
considered customer pay. No labor operation is provided.

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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