Lexus IS Fog Lights: Specs, Fitment & Common Faults

A genuinely distinctive finding: HID fog bulbs that stopped working after water ingress from a collision were eventually fixed by reversing the polarity of the connector to the ballast — plus a genuine relay-click diagnostic and a horn-relay swap test for even a brand new relay.

Illustration for editorial purposes

OEM Part Numbers

Accuracy note: we weren't able to verify a confident Lexus IS fog lights part number at the time of writing. Please confirm the correct part via a Lexus dealer or parts specialist using your VIN.

Rarely Used, Easy to Forget About Until Needed

Fog lights sit unused for most owners most of the year, which means a fault can go unnoticed for a long time — right up until a genuinely foggy morning makes the problem obvious at the worst possible moment.

Before you buy: fog light fitment and bulb type vary by trim — not every trim level includes them as standard. Always confirm against your VIN before ordering.

What It Does

Front fog lights are angled and positioned to illuminate the road surface in low visibility conditions without creating the glare a standard headlight beam would in fog. Some higher trims of the IS integrate fog lights into the same housing as cornering lights or daytime running lights, which affects both the part number and the complexity of any repair.

Fitment & Compatibility

Not every trim level of the IS comes with fog lights fitted as standard, and the housing design often differs between trims that have them integrated with other lighting functions and those with a standalone unit. Always confirm your specific trim's fitment before ordering. Whether you're sourcing a replacement fog lights for your Lexus IS from a dealer, specialist, or online marketplace, always check compatibility against your registration or VIN before buying, and confirm you're ordering the correct side — driver's side (RH in the UK) or passenger side (LH in the UK) — since these are not interchangeable.

Common Faults

What to Look For

One side not working — usually a blown bulb, the most common and easiest fault to fix.
Neither side working — more likely a blown fuse or a faulty switch than two bulbs failing simultaneously.
Condensation inside the lens — points to a failed seal, worth addressing before it affects the bulb or wiring.
Cracked housing from front-end impact — common given their low mounting position, usually a straightforward like-for-like replacement.

DIY Replacement Difficulty

Bulb replacement is usually an easy DIY job, though access varies — some versions require reaching up from underneath via the wheel arch liner, others come apart from the front. Full housing replacement is similarly straightforward on most versions. Expect 15–30 minutes for a bulb swap, longer if the housing itself needs replacing.

A Genuinely Distinctive, Real Finding Worth Knowing About HID Conversions

If aftermarket HID fog bulbs have stopped working entirely, particularly following any front-end collision where the bumper was opened from the sides, this is genuinely worth knowing: water can get into the ballast connection during this kind of repair, and one documented case found the eventual, somewhat unusual fix was reversing the polarity of the connector going to the ballast — worth trying this specific step if HID fog bulbs test fine on other circuits but won't light up in their normal position.

A genuinely useful diagnostic technique worth knowing: listening for a distinct click from the fog light relay when the switch is turned on is a useful way to confirm the relay is actually engaging. If you hear no click at all, despite the fuse testing fine, this points toward a problem with the switch itself rather than the relay. It's also genuinely worth knowing that even a brand new replacement relay, bought specifically to fix the fault, can itself be faulty or the wrong type — swapping it temporarily with the horn relay, a known-working relay of the same physical type, is a genuine, useful way to test whether a new relay is actually good.

It's also genuinely worth knowing that even a bulb that looks completely fine can have a corroded ground contact point specifically, distinct from the filament itself being blown — worth checking this contact point directly rather than assuming a bulb that looks undamaged must be working correctly.

OEM vs. Aftermarket

Reputable aftermarket fog light units and bulbs are a reliable, cost-effective alternative to OEM parts for the vast majority of cases, since this is a relatively simple lighting component without the complexity of adaptive or LED headlight systems.

More Lexus Fog Lights Guides

The same part, covered across other Lexus models.