Number Plate Lights

[tony574]

Hi all,

I had a message come up saying "check license plate lights", are sure enough the bulbs had blown.

purchased the new bulbs and replaced but still have no lights and the message remains.

I cant find a fuse that powers the number plate lights...

Any thoughts on a fuse?, or things to check?

thanks for any help

[Loren]

Power comes through the rear control unit - so other things would not likely work if the fuse were blown.

Check for a good chassis ground at the lights - these are know issues on the early Cayennes'.

[tony574]

Thanks loren.

I recently changed a rear light bulb so maybe that is the key to it

Thanks for the tip!

Cheers

[tony574]

Hi loren,

Any pointers where the ground is located?

I took off the number plate lights and their are two wires on the plug that go onto the number plate light unit.

All looks ok, no dirt, no rust, no damage..

Do i just test the ground wire from the plug, or is there a central ground for the rear control ?

Thanks for any help

[Loren]

There are ground points at each rear taillight housing.

[tony574]

I must be looking in the wrong place. I cannot see any ground on the rear light unit.

Today, i looked at the number plate units again.

Checking with the tester i can confirm the light units are both ok as i get a connection sound using the multi-meter

however, when connecting the tester to the two wire on the car i get no reading when the car lights are switched on?

its either bad earth or no voltage getting through..

any more pointers (sorry to be think!!)

tony

[Loren]

There are ground points at each rear taillight housing.

[tony574]

Thanks,

i have looked in these places now and still found no issues...ill keep looking

[Loren]

If all grounds and all connectors look and test good (low resistance) then you will likely need a PIWIS tester to check and re-program the rear control module.

Sometimes these control modules get a transient spike that upsets the system and requires a re-program - does not happen often but I've seen it a few times.

[markwest]

Hi all

I had the same problem with rear number lights not working, I searched nearly every site I could find in the hope of finding a way to fix as in the UK we must have a number plate light working. After checking all fuses and bulbs I brought a high spec obd scanner and writer expecting to find one of the control units had failed but this wasn't the case. The mot was nearly up so I discided to run a cable from my real lights just to pass the mot. I know I would still have the error but happy to put up with for now. So I got to work and found the problem. I found a broken cable where the cables come from the boot to the car. 

I've attached a link of photos 

Cayenne - Google Drive

DRIVE.GOOGLE.COM

 

Edited December 14, 2021 by markwest