As in the title, I took car for MOT today, passed on everything (including dodgy patched exhaust) and it failed on inoperative rear fog lights!
I checked bulbs, they are fine, I checked fuse in the boot, that's fine as well, the light on the switch doesn't come on as well! I'm getting desperate and considering just quickly wiring another cable, just to get it through MOT! But any suggestion would be appreciated!


Oh, by the way, I have a spare circuit board for the light switches, I tried swapping them, with the same result! No rear fog lights!


And I just realised I wrote RAER instead of REAR!!!!

 

Voltage for the rear fogs comes from relays inside the rear lamp control module. The ground path/earth path to energize the relays comes from the dashboard switch, via the body processor module.

If you have a test light or meter a few checks could be made....which I can try to describe after a couple cups of coffee.

Cheers
DD

 

Yes, I do happen to have the test light, and if needed I have access to the multimeter! Electrical components always seemed to be rather complicated to me :-/

 

Looks like the purple/light green wire from the switchpack should be "ground" when the fog lamp switch is turned on. This wire goes from the switch to pin 45 of the body processor module (look for the black 48 pin connector).

The ground signal leaves the body processor on the red/blue wire, pin 47 of the yellow 48-pin connector. The red/blue wire goes to the rear lamp module to energize the internal fog lamp relay (pin 15 of the black 20 pin connector at the lamp control module in the boot)

More later, gotta get to work!

Cheers
DD

 

Ok, I checked the cables as you said, and the purple/light green cable seems to provide the 'ground' to the body processor module. But when I looked at the rear lamp module, there were 2 red/blue cables (I tested them both, since I couldn't find numbers on connector) and it seems that there's nothing getting from body processor module to the rear lamp module. Which reminds me of a little mistake I made once, last year... https://www.jaguarforums.com/forum/x...up-help-85053/ which could mean, that I fried something in the body processor module by accident and that thing might have been responsible for rear fogs. So my plan is just to run a separate cable from the purple/light green cable at the front, with a relay to the fogs, and just get over with it. I have just 10h left for doing the free MOT retest to keep the car legally on the road, and only 5 days until I'm hitting the road (this time for sure) and driving from UK to Poland. So this time there's no stopping me, those stupid fogs will not make it fail again!

 

Ok, sorted without bypassing the modules! It's good when my brain actually works from time to time, hate working nightshifts... So, when I cut all the wires last year in order to sort out the problem of permanently illuminated dials, I reconnected them with sort of a quick connectors... Somehow I managed to get the purple/light green connected tightly but with the insulation only... That's why I thought there was power going to the body processor module but not out of it, if it makes any sense... Anyway, I can happily announce that El Gato Grande passed the MOT without any additional advisories, which I actually expected (well, you know, exhaust heavily patched up with exhaust repair paste, one of the tires looking like it's been on the car since 1995, and some other things).