I've probably made the rookie mistake with canbus spot lights but can anyone confirm?
Before I waste hours belling out the car loom for a non-existent fault, can anyone confirm if the canbus expects to see a halogen bulb load?

100HP OEM front spot lights were rusty with blown bulbs so removed for MOT. There was no bulb fault warning. The panel switch works and warning light appears on dash.

I dont want another set of OEM lights which will rot just the same. Instead fitted LED spot lights which tested out fine on the battery. However they dont work when plugged into the car wiring (I used the correct connectors).

I'm guessing you mean the foglamps mounted in the front bumper. Foglamps should only illuminate with side or headlamps, but if the green warning lamp is on, that should be working fine.
If there was no failure warning, I'd guess that there is no Canbus sensing, so any lamp should be fine. That's the theory.
I'd never used my foglights, having never found any foglights to be of use. To reduce dazzle from headlamps in fog, I use the height adjuster to lower them, works for me.
When one of my foglamps caught a stone, rather than replace it for around £60, for a lamp I'd never use, I replaced them with DRLs, which of course needed their own bespoke wiring. Just had to replace those due to ageing, sadly timing just wrong, as I was inside the bumper, so could have got at the foglight wiring only 10 days ago. If I can get myself motivated, I may be able to pop out one of them and see what the foglight wiring does for me with original lamp compared to maybe a 5w bulb. (Can't promise)
Looking at the wiring diagram, the foglamps are fed via a relay, presumably in the underbonnet fusebox. This is switched by the body ECU, but strangely, instead of just providing a feed that earth's somewhere, both connections go to the ECU, one via a 'Short circuit coupling'. No idea what that looks like, or where to find it.
Power comes to the relay by apparently Fuse 30.

Thanks Bill that's helpful.

The relay output simply drives both lights so looks like CanBus is not involved in bulb sensing. I'll have to check the relay etc.

Maybe I will wire in a new switch and relay.

what happened if you take the LEDs back out?

are you seeing a canbus error?


First post doesn't read the same as when I first read it.

koalar said:

what happened if you take the LEDs back out?

are you seeing a canbus error?

First post doesn't read the same as when I first read it.

Click to expand...

I probably edited the original post before anyone commented. Sorry.

The dash switch works and the dash info light works. There is no can bus bulb error (as with a side light out). I have not run MES to look for canbus faults so wanted to know if the relay output is sensed in some way.

The old OEM fog lamps were corroded and leaking water as they generally do. I have removd the old lamps and fitted LED pencil beam spots into the plastic housing and wired with the original type waterproof connectors. They should be coming on with the side lights but nothing happens. They tested out fine before plugging into the wiring loom. But I forgot to bell for power from the loom before putting the bumper back on the car.

DaveMcT said:

I probably edited the original post before anyone commented. Sorry.

The dash switch works and the dash info light works. There is no can bus bulb error (as with a side light out). I have not run MES to look for canbus faults so wanted to know if the relay output is sensed in some way.

The old OEM fog lamps were corroded and leaking water as they generally do. I have removd the old lamps and fitted LED pencil beam spots into the plastic housing and wired with the original type waterproof connectors. They should be coming on with the side lights but nothing happens. They tested out fine before plugging into the wiring loom. But I forgot to bell for power from the loom before putting the bumper back on the car.

Click to expand...

Led only work one way round.

I would take them both out

make sure there's voltage on the connector

then try one at a time.

koalar said:

Led only work one way round.

I would take them both out

make sure there's voltage on the connector

then try one at a time.

Click to expand...

They worked fine before I refitted the bumper but I did not check which side is earth on the wiring loom connectors. As said, rookie mistake.


I want to avoid the hassle of pulling it apart only to find it's a canbus issue. Bill's wiring diagrams solves that question so it's another fight with those hateful wheel arch liners.

DaveMcT said:

so it's another fight with those hateful wheel arch liners.

Click to expand...

I can get my foglight housings out from the front, without disturbing the wheelarch liners.
The two little hex key scres come out, then the two torx under the bumper. Lever the housing out from the inner edge first, then the top, then it should tilt and come out.

DaveMcT What LEDs did you use, and....did you get this fixed?