GM Upfitter Switches: Wiring, Amps and Install Guide

GM upfitter switches are a bank of factory-supplied auxiliary switches, ordered under regular production option (RPO) 9L7 on Chevrolet Silverado and GMC Sierra trucks, that give you protected, relay-controlled circuits for added equipment such as warning lights, work lights, compressors and plow controls. On many full-size trucks the switches are only part of the package: you still need the console cover, fuse kit, auxiliary fuse block and harness to make them work, and GM directs installers to specific upfitter bulletins by trim. This guide explains what the system is, where it sits in the truck, what the circuits are rated for and how to connect an accessory properly.

TL;DR

• Upfitter (auxiliary) switches are an OEM switch bank, RPO 9L7, that controls relay-driven outputs for aftermarket equipment without cutting into factory wiring.
• On 2022 and newer full-size Chevrolet trucks, the option often needs a switch bank, fuse kit, auxiliary fuse block and harness installed before it works. The procedure depends on trim.
• Output pairs can be set to battery power or ignition-switched power by moving fuses in the auxiliary fuse block, so decide how each accessory should behave before you wire it.
• Use the GM Upfitter Integration bulletin that matches your model year and trim, and have a qualified installer do the work. Labour is not covered by GM warranty.
• Warning-light legality depends on your province or state, and a switch does not authorize any light to be used.

Table of Contents

• What an upfitter switch is
• Which GM trucks offer them
• Where the switches, fuse block and wiring are located
• How the circuits are powered and protected
• Adding upfitter switches when the truck did not come with them
• Connecting warning lights and other accessories
• Legal use is a separate question
• Where SMR fits
• FAQ
• Sources

What an upfitter switch is

An upfitter switch is a factory-engineered way to add a controlled power output to a truck. Instead of splicing into a dash harness or running a toggle switch through a hole you drill yourself, you use switches that the vehicle’s electrical architecture already recognizes. Each switch drives a relay, the relay feeds a fused output, and the output goes to your accessory.

Owners of a 2020 GMC Sierra describe the bank as five switches for things like plow equipment, external lights and compressors, and the same idea applies across the GM full-size range, as seen in one owner’s install write-up on a GM truck forum. Treat that as a real-world description, not a specification. The specification comes from GM’s own upfitter bulletins, which are written for professional technicians.

The terms are used loosely online. “Upfitter switches”, “auxiliary switches” and “aux switches” all describe the same idea on Chevrolet and GMC vehicles, and RPO 9L7 is the build code that identifies the switch bank option. The code is the most reliable way to confirm what your truck has, because trim names and marketing language change between model years.

Which GM trucks offer them

GM has offered the 9L7 option on Silverado 1500, Silverado HD and Silverado Medium Duty, with GMC Sierra equivalents. Early installations on Silverado and Sierra 1500 trucks from the 2014 to 2018 period were supported by a GM technical bulletin, PIT5298B, issued in 2017, covering installation of upfitter auxiliary switches. For the 2019 Silverado Medium Duty 4500HD, 5500HD and 6500HD, GM Upfitter Integration Bulletin 148e describes a 9L7 switch bank that places the switch outputs at the left-hand instrument panel junction block.

Availability by model year and trim changes, and not every Canadian-market truck was built with the same content as a US one. Before you buy parts, confirm your truck’s RPO list (the service parts identification label in the glovebox lists the codes) and ask a GM dealer’s parts department which components your VIN needs.

Where the switches, fuse block and wiring are located

Locations depend on model year and trim, so use the bulletin for your vehicle. The current full-size example is GM Upfitter Bulletin 205, which covers 9L7 on higher trim levels. In that procedure:

• The switches are fitted in the console panel.
• The auxiliary fuse block mounts under the driver’s-side HVAC extension duct.
• The power harness passes into the cab through a service port, reached by removing the left-hand inner wheelhouse liner.
• The power cable ring terminal connects to a 60-amp fuse output stud in the battery-mounted electrical center.

Some configurations use a different layout. GM Upfitter Bulletin 164 describes overhead auxiliary switch banks, RPO UEH, mounted in the headliner and providing 20-amp switched outputs for vocational equipment. That is a useful option for vehicles where the console is occupied by a radio head, a laptop mount or a push-to-talk setup.

The forum question “where are the upfitter wires?” has a short answer: look for the GM-supplied upfitter harness and fuse block rather than hunting for a generic accessory wire. If the truck arrived with the switches already installed and powered, the outputs are normally available at the fuse block or junction block named in the bulletin for that model.

How the circuits are powered and protected

The question fleet managers ask most is how many amps a circuit can handle. There is no single answer across all GM vehicles, and you should never assume one. The figures GM publishes differ by platform:

Two habits keep an install safe. First, size the load to the circuit, not the switch. A single output rated at 30 amps still shares a supply with other outputs, so add up everything that can be on at once. Second, fuse at the source and use wire gauge suited to the run length and current. If the combined load of several lights and a controller approaches the rating, add a dedicated relay and a separately fused feed rather than stretching the factory circuit.

Battery power or ignition power

GM sets the power behaviour in pairs, using fuse position. In Bulletin 205, the 9L7 switches can be reconfigured in pairs to work from battery power or only with the ignition in accessory or on by relocating fuses within the auxiliary fuse block. Bulletin 110N describes the same pairing approach, with battery or ignition 12V+ set by fuse placement in the under-hood electrical center. The 2019 medium duty bulletin adds a warning that matters in practice: do not populate both the battery and ignition fuse locations for the same pair at once.

That pairing has a planning consequence. If switches 1 and 2 are set to battery power, both can operate with the key off. A work light you want available at a job site with the engine off suits that setting. A warning light that should shut down when the driver leaves the truck is better on the ignition-switched pair. Decide this on paper before you open the fuse block.

Adding upfitter switches when the truck did not come with them

This is where most of the search interest comes from. A common complaint on owner forums is that the switches are ordered but the truck arrives needing a harness and fuse kit. That matches GM’s own position: beginning with 2022 full-size trucks, 9L7 often requires components such as a console cover, switch bank, fuse kit and wiring harness to become functional. Bulletin 205 also states that labour is not covered by GM warranty or pre-delivery inspection, and that the procedure depends on trim.

The bulletins split by trim:

• Bulletin 193d lists procedures for WT, Custom, LT, RST, ZR2, LTZ, High Country, SLE, Elevation and SLT trims. AT4, AT4X and Denali procedures were to follow in a later revision.
• Bulletin 205 covers those higher trims.
• A GM notice dated 2026 for the listed 2022 to 2025 Silverado models says 9L7 installation information may not be readily available in Service Information and directs installers to Bulletin 193 or 205, depending on trim.

Bulletins are revised, so download the latest version from GM Upfitter Integration rather than relying on a copy someone posted to a forum.

Typical installation sequence

This is an overview of the order of work, not a substitute for the bulletin.

1. Confirm the RPO codes and trim, and pick the matching bulletin.
2. Disconnect the battery and follow the bulletin’s safety steps for the vehicle.
3. Remove the trim and the left-hand inner wheelhouse liner to reach the service port.
4. Route the power harness through the port. Bulletin 205 notes that the fabric-like tape must stay on the wire after the conduit or insulation is removed.
5. Connect the power cable ring terminal to the 60-amp output stud in the under-hood electrical center.
6. Mount the auxiliary fuse block under the HVAC extension duct and fit the switch bank in the console.
7. Set the fuses for battery or ignition operation in each pair.
8. Wire your accessory to the output, with its own inline protection where the accessory needs it, and test every function before reassembling.

Connecting warning lights and other accessories

A switch bank gives you on and off. It does not give you flash patterns, synchronization or multi-light control. For a single beacon or a pair of surface-mount strobes, one auxiliary output may be enough. For a full vehicle package with a light bar, grille lights, a rear traffic advisor and scene lighting, a dedicated controller is usually the cleaner approach, with the upfitter output acting as the switched power feed or trigger.

Our Ram auxiliary switch wiring guide walks through the same logic on another platform, and the principles of fusing, relays and grounding carry over. If you are building out a general panel, see our notes on switch panel wiring. Fleets outfitting service bodies can also read about utility truck lighting.

A few practical points from years of fleet work:

• Confirm the load. Read the amperage on the light’s data sheet or product page, then total it for the circuit.
• Keep grounds short and on clean, bare metal or a purpose-built ground point.
• Label each output at the fuse block so the next technician knows what it controls.
• Test with the engine running and the headlights, heater and wipers on, because voltage drop shows up under load.
• If a light flickers or a controller resets, work through the steps in our vehicle lighting troubleshooting tips.

Compatibility with GM’s own systems is specific to the vehicle. We do not claim any SMR product is guaranteed to integrate with a proprietary vehicle system, so check the product listing and the relevant bulletin, and contact us if you want a second opinion on a configuration.

Legal use is a separate question

Having switches that can power a light bar is not the same as being allowed to run one. Which colours, flash patterns and vehicle types are permitted depends on your province or state, and often on your role: a volunteer firefighter, a tow operator and a snow-removal contractor can face different rules. Check with your provincial transport ministry or state motor vehicle authority before you mount or operate any warning light, and keep any permit or authorization from your fire chief or employer on file. Buying a product from us does not authorize its use.

Where SMR fits

SMR is a Canadian-owned supplier and retailer based in Ottawa, founded by a former Highway Patrol officer and fleet safety professional. We carry LED light bars, surface-mount strobes, beacons, traffic advisors, controllers and accessories across our Patrol, Fleet and Signal lines, and we support custom configurations and commercial fleet orders. If you are planning a GM truck build, browse the range at StrobeMyRide.ca and contact our team with your truck’s year, trim and the equipment you want to run. We will help you match lights and controllers to the circuits you have. Product specifications, certifications, warranty terms and compatibility vary by SKU, so verify them on each listing.

FAQ

What is an upfitter switch?

It is a factory-style auxiliary switch that controls a relay and fused output for aftermarket equipment such as lights, compressors or plow controls. On Chevrolet and GMC trucks the option is coded RPO 9L7. It lets installers add equipment without tapping into unrelated vehicle wiring.

Does Chevy have upfitter switches?

Yes. GM documents auxiliary switch banks for Silverado light-duty, heavy-duty and medium-duty trucks, and GMC offers matching Sierra equipment. Which trims and model years can take the option varies, so check your RPO codes and the GM Upfitter Integration bulletin for your truck.

How many amps can GM upfitter switch circuits handle?

It depends on the platform. GM documents 30-amp outputs on the 2019 Silverado Medium Duty 9L7 bank and on the Tahoe PPV/SSV system, and 20-amp outputs on the overhead switch bank. Read the bulletin for your vehicle and total the connected load before wiring.

Can I add upfitter switches to a truck that did not come with them?

On 2022 and newer full-size Chevrolet trucks, the 9L7 option often needs a switch bank, fuse kit, auxiliary fuse block and harness fitted before it works. GM points installers to Bulletin 193 or 205 by trim. Ask a GM dealer which parts your VIN needs, and use a qualified installer.

Can the switches run on ignition power only?

Yes, in pairs. GM’s bulletins describe moving fuses in the auxiliary fuse block or under-hood electrical center to choose battery power or ignition-switched power for each pair. Follow the fuse positions in your bulletin exactly.

Sources

• GM Upfitter Bulletin 205: 9L7 auxiliary switches, higher trim levels
• GM Upfitter Bulletin 193d: 9L7 procedures by trim
• GM Upfitter Bulletin 148e: Silverado Medium Duty 9L7
• GM Upfitter Bulletin 164: overhead auxiliary switch bank
• GM Upfitter Bulletin 118c: Tahoe PPV/SSV
• GM Upfitter Bulletin 110N: battery or ignition configuration
• GM bulletin PIT5298B: installation of upfitter auxiliary switches
• GM notice on 9L7 installation information, 2022 to 2025 Silverado
• Owner install write-up, GM-Trucks.com forum

Recommended

• Ram aux switch wiring: the complete upfitter guide
• Switch panel wiring for vehicles, boats, and campervans
• Warning Light Controller Switch Box Guide
• How to Wire Traffic Advisors Properly

Information provided by Strobe My Ride is intended for general educational purposes only. Vehicle warning-light regulations, permitted colours, installation requirements and product certifications vary by jurisdiction and application. Always verify applicable laws and product specifications before purchasing, installing or operating warning-light equipment. For product-specific assistance, contact sales@strobemyride.ca