What fog light bulb does a Chevy Silverado use?

On the 1999–2007 (GMT800) trucks the fog lamp is an 880. On 2007–2013 (GMT900) and 2014–2018 (K2XX) trucks it's most commonly the 5202 — the same bulb sold as H16, 9009 or 2504 depending on the brand, all the same socket. Many 2019-plus (T1XX) trucks and higher trims left the factory with sealed LED fog lamps that have no replaceable bulb, in which case you replace the housing rather than a bulb. Fog housings changed by trim as well as by year, so confirm against your specific truck before you buy.

Why do my Silverado's fog lights turn off when I use the high beams?

That's normal on most Silverados, not a fault. The factory wiring drops the fog lamps out when the high beams come on — fog lamps are designed to work under a fog or dust layer with the low beams, and running them with high beams just bounces more light back at you. If your fogs don't work with the low beams either, then start diagnosing: fog fuse and relay first, then the connectors at the bumper (they sit low and take road spray, so corroded terminals are the most common real failure), then the switch itself.

Can I add fog lights to a Silverado that didn't come with them?

Yes, and it's one of the most common Silverado retrofits — but budget for more than a pair of lamps. The bumper valance on a truck built without fogs carries blank filler panels that have to be swapped for the fog bezels, and you need the lamps, the fog-lamp harness and relay, and a headlight switch with the fog function (on the GM trucks the fog switch is part of the headlight switch assembly, not a separate button). On later trucks the body control module may also need the fog-lamp option enabled with a scan tool before the circuit will do anything. Sourcing a factory-optioned switch and harness from a donor truck on eBay Motors is usually cheaper and cleaner than an aftermarket bodge.

Do Silverado 1500s come with cab roof marker lights, and can I add them?

Generally no on a 1500. Factory cab clearance lamps show up on the wide-body trucks — dual-rear-wheel 3500s especially — because federal lighting rules require clearance lamps on vehicles 80 inches or more in overall width. A 1500 is under that, so it leaves the factory with a clean roof. You can add them, but understand what it involves: an OEM-style five-lamp kit needs holes drilled through the cab roof and a wiring pass into the headliner, and that roof is already the panel where Silverados are famous for leaking at the third brake light. Drill precisely, seal properly with butyl and a quality sealant, and expect to be chasing water forever if you rush it.

Silverado Fog Light & Cab Marker Light Guide: Bulb Sizes, Retrofits & What's Actually Legal

Everyone starts with headlights. But the two lighting jobs that actually separate a truck that’s been thought about from one that’s been shopped are the ones below and above the beam: the fog lamps in the bumper, and the cab roof marker lights on top. One is a genuine visibility tool that most owners misunderstand, and the other is a look that carries real fitment and leak consequences.

This is the third piece of the front-lighting funnel, alongside the LED headlight guide and the position-by-position bulb size reference. The rear of the truck — tail lamps and the cab-leaking third brake light — is covered in the tail light & CHMSL guide. For new fog bulbs and LED kits the lighting category is the Amazon side; for OEM housings, factory-optioned switches and harnesses, and complete cab-light kits, eBay Motors is the real marketplace — that’s what the live listings above are.

Fog bulb sizes by generation

Generation	Years	Fog bulb
GMT800	1999–2007	880
GMT900	2007–2013	5202 (H16)
K2XX	2014–2018	5202 (H16)
T1XX	2019+	5202 on halogen trims; factory LED on many trims — no serviceable bulb

Two things trip people up here:

The 5202 has half a dozen names. It’s sold as H16, 9009, 2504, and occasionally packaged next to PS19W/PSX24W parts. Same socket. Buy on the 5202 number and ignore the marketing on the box.
Trim beats year. GM changed fog housings across trims within the same model year, and higher trims — plus a lot of 2019-plus trucks — got sealed LED fog lamps with nothing to unscrew. If you pop the wheel-well liner and find no bulb collar, you’re replacing a housing, not a bulb. That’s the same “spec varies by trim, not model year” rule that governs the whole generations and fitment reference.

What fog lights are actually for (and why yours cut out)

A fog lamp is not a small headlight. It’s mounted low and throws a wide, flat beam with a sharp horizontal cutoff, deliberately aimed under the fog, dust, or snow layer so light travels along the road instead of reflecting off the airborne particles back into your eyes. That’s the entire design brief, and it explains the two behaviors owners misread as faults:

They shut off with the high beams. On most Silverados the factory circuit drops the fogs when you flip to high beam. This is by design, not a broken relay.
They look weak from the driver’s seat on a clear night. They’re supposed to. A fog lamp that lights up the scenery is aimed too high and is blinding oncoming traffic.

When fogs genuinely don’t work, work the circuit in this order — cheapest and most likely first:

Fuse and relay. Both live in the underhood fuse block; the lid diagram labels them. Swap the fog relay with an identical relay from a non-critical circuit to test it for free.
The bumper connectors. This is the real answer most of the time. Fog lamp pigtails sit inches off the pavement and eat road spray, salt, and car-wash chemicals for a decade. Green corrosion on the terminals, or a brittle cracked connector, gives you the classic one-fog-works-one-doesn’t. Clean, dielectric-grease, or replace the pigtail.
Grounds. A fog lamp with a marginal ground goes dim and yellow before it goes dead. Chase the ground strap to the core support and clean the contact surface to bare metal.
The switch. Last, because it’s the most expensive. On these trucks the fog function is built into the headlight switch assembly, so “the fog switch is bad” means replacing the whole switch.

If you’re already chasing electrical gremlins across the truck, the common problems by generation guide covers what else fails on your platform — worth reading before you take the bumper apart twice.

Retrofitting fog lamps into a truck that never had them

Work trucks and base trims came out of the factory with blank filler panels where the fog lamps go. Adding fogs is a genuinely worthwhile upgrade, and it’s a bolt-in job in the sense that GM already engineered the mounting points — but the parts list is longer than “a pair of lights”:

Part	Why you need it
Fog lamp housings (pair)	The lamps themselves. OEM take-offs give the factory look and correct beam cutoff.
Fog bezels / valance inserts	The blanks in your bumper have no opening. These are trim-and-year specific — the single most commonly forgotten part.
Fog harness + relay	The truck was built without the circuit downstream of the fuse block on many configurations.
Headlight switch with fog function	The fog switch is integrated into the headlight switch on these trucks, so a non-fog truck’s switch physically can’t turn them on.
BCM enable (later trucks)	On newer platforms the body control module may need the fog-lamp option turned on with a scan tool before the output goes live.

The cheap, clean way to do this is to buy the factory-optioned switch, harness and bezels off a donor truck rather than assembling an aftermarket mishmash — the OEM parts fit the bumper openings correctly, keep the factory beam pattern, and don’t leave you with a toggle switch zip-tied under the dash. That’s exactly the kind of used/OEM hunting eBay Motors exists for; the retrofit-kit search button above is aimed at it.

A note on light bars and pod lights: a bumper-mounted light bar is not a fog lamp substitute. It’s an off-road lamp — un-aimed, no cutoff, and illegal to run on public roads in most places without a cover. Run one if you actually go off pavement, but wire it through its own switch and don’t expect it to replace a working fog circuit.

Going LED on the fogs

The fog position is a better LED candidate than the headlight position, for one reason: fog housings are generally simple reflectors with a shallow, forgiving beam, and the fog cutoff comes largely from the aim rather than a precision projector. Still, the same rules from the LED headlight guide apply:

Match the emitter to the filament location. A cheap LED bulb that puts its chips in the wrong plane throws light everywhere except down the road, and a bad beam pattern in the fog position blinds oncoming traffic from below — the most annoying variety.
Color: white or selective yellow. Both are road-legal essentially everywhere for fog lamps, and selective yellow genuinely works better in falling snow and heavy fog — less glare-back off the particles. Blue-tinted 8000K “ice” bulbs look modern in a parking lot and perform worse in the exact conditions the lamp is for.
Watch for flicker and bulb-out warnings. Lower current draw can upset the circuit the same way it does at the rear. If you get flicker, a decoder/anti-flicker harness on that circuit is the fix.
Re-aim afterwards. Any bulb or housing change moves the cutoff. Park 25 feet from a wall on level ground and set the top of the beam so it falls below the height of the lamp itself. If your fogs light up the wall at headlight height, they’re aimed wrong.

Cab roof marker (clearance) lights

Those five amber lamps across the top of the cab are clearance lamps, and they exist for a legal reason rather than a stylistic one: federal lighting rules require clearance lamps on vehicles 80 inches or more in overall width. That’s why they show up on the wide-body trucks — dual-rear-wheel 3500s in particular — and why a 1500 comes with a bare roof.

If your truck has them and one is dark, the fix is usually trivial. Most GM roof marker lamps use a small 194-type wedge bulb (confirm yours before ordering a five-pack), and the lens pops off with one or two screws. Two failure modes dominate:

Cracked or UV-hazed lenses. Amber plastic bakes on the roof for fifteen years and goes brittle and pale. New lenses restore the look and, more importantly, restore the seal.
Corroded sockets from a leaking lens. Same story as the tail lamps — water gets in, the contacts go green, and the lamp works intermittently. Replace the lens and the gasket, not just the bulb.

If you’re adding them to a truck that never had them, be clear-eyed about what the job is. An OEM-style five-lamp kit requires drilling five holes through the cab roof and running wiring into the headliner. That roof panel is already the one Silverados are notorious for leaking through at the third brake light — you are about to make five new penetrations a couple of feet from a known leak point. If you do it:

Mark and drill precisely, deburr every hole, and prime the bare edges so they don’t rust from the inside out.
Seal with butyl tape under the lamp base plus a quality sealant at the fastener, not a smear of silicone over the top.
Run the wiring so it can’t chafe on a roof brace, and pick up a switched, fused source — tapping the parking-light circuit is the factory-correct behavior, since clearance lamps are meant to be on whenever the marker lights are.

Legality, briefly: forward-facing clearance lamps must be amber, rear-facing ones red. Running white cab lights, or running amber lamps facing rearward, is the kind of thing that draws attention in an inspection state. If the truck isn’t 80 inches wide the lamps aren’t required — but if you install them, they still have to follow the color rules.

Where to buy which part

Fog bulbs, LED fog kits, anti-flicker harnesses, lens restoration kits — new consumables, the lighting category and the Amazon side.
OEM fog housings, factory-optioned headlight switches, fog harnesses, bumper bezels, complete cab-light kits and replacement amber lenses — used and OEM take-off territory, which means eBay Motors. Housings and switches for a discontinued trim frequently don’t exist as new parts at any price, and the donor-truck market is the only place they surface. That’s what the live listings and the search buttons on this page are pointed at.

Get the fitment right first, buy the correct part second. On a truck this common, almost every fog and marker part you need has already come off someone else’s Silverado.