Intermittent Tail, License plate lights and fog lights failu
 

Hello all, I have this Intermittent both Left and right Taillight License plate lights and for lights failure, but Head light, Hazard and brake lights working.

1. While all lights working, voltage is present in whole Tail light cluster. Have Good earth.
2. While the above lights are not working, no voltage in the Taillight, fog light, and License plate wires but Head light works but earth is good. Also there is voltage in Brake, reverse light. Front Head light is not affected at all in all situation.
3. Fuse is not blown, which is number 2 at the REM, checked the fuse at both ends power is passing through fuse.
4. Iam eliminating earth issues because Left and Rear cluster has separate earth.
5. I removed the Control knob in switch in the front panel and had it a good clean. There are 3 wires Red, brown and green/white- which is fed in this unit which has voltage irrespective of lights working or not working.
6. But when the above lights are not working the Control knob small light is not working either.


Could someone please point me to the right diagnostic direction.
Mean while I ordered a used control knob from ebay.

Thank you.

[IMG]https://i.ibb.co/9pktPky/Head-llight-switch-knob.jpg[/IMG]

It is more than likely the light switch unit has gone bad, all being well your ebay one should cure it, happened to my s60 d5, only had half the dash lights and no control over the headlights, a new second hand switch cured this.

Thanks for the reply. Will update when I fit the replacement.

Is this for the XC90 ? May want to look closely at the harness passing from the trunk lid for the car frame, the wires may break inside their plastic jacket. May try a continuity test while moving the harness by hand. Maybe also look closely at the REM for any water ingress. Look near the battery as well for any corrosion at cables and electric boxes

Yes . It is for Xc90.
I've tried the continuity by wiggling wires.
Look like that switch control knob circuit problem.
Just found out turning on and off the knob also affects the intermittent fail. But then CAN bus diagnosis, Iam not expert.

I might need some expert advise like you, SwissXC90 and experienced members, if tomorrow's knob replacement didn't work.
[IMG]https://i.postimg.cc/C1fhygNJ/20201025-131223.jpg[/IMG]

Thank you again....

Just to reconfirm the issue after replacing the LSM is below.

Intermittent rear tail light, fog and license plate not working.

While switched on Headlights, reverse light, Hazard lights work but not* tail lights, license plate light and fog lights.* This is intermittent.

Replaced the Light switch module from eBay but still the same issue.

Just found out , this happens when the car engine is running. Its works fine at the first start but when turned off and On 3 times same time , the light in the LSM goes of with all rear lights as mentioned above will go off until I restart the car to make it work.

Please let me know where to look and diagnose, bulb socket, LSM, CEM or anything else please.

Fuse in REM is good.