On a new to me 2008 GL320 CDI I have no trailer lights and when I scan the rear SAM I get

"914B - component F4kL (trailer circuit 30X relay) is defective or missing or the feed line has open circuit "

I am wondering which is component F4kL, I have a fusebox diagram which points to location L in the rear compartment (for 30x) but that is empty, I have a nearly identical car -Wife's- (with working trailer lights) and it has nothing in this location either, I have a rear fusebox (from a damaged car) and it has nothing in that location but I was able to put another relay (same pin locations) from the "spare" fusebox into L and still nothing - same code - stored and current

At the trailer socket (on towbar) get phantom readings of around 3-4v to indicators, tail, brake lights etc when I turn on the car tail lights only - even when I turn them off I get these phantom readings - This eventually times out maybe 5 minutes after turning off the lights. when nothing from trailer socket.

I see that there has been water damage around the rear SAM (in the past - now dry) but the water appears to have only got to the level of the bottom of the SAM mounting plate only (and the cover was over the SAM - and looks fine - also there is a factory Subwoofer over it as well - and it too looks like never wet) - So I am wondering if the relay is to blame at all?? There is nothing else happening - all seats and lights etc work - no other codes (except 924A fuel filler flap CL motor) which I think the motor has failed - flap is never locked (but I will investigate this tomorrow - perhaps not motor but SAM?)

When I unplug the black trailer harness plug from the SAM I get no readings at all from the trailer socket (the phantom readings go away)

I have not yet unplugged all the SAM plugs and pulled it out/apart as I am concerned I might damage it - and it might not be the cause. and the trailer lights are really the only thing (fuel flap motor still worries me)

The past water damage is on both sides of car (showing on the white sound deadening) but the pan under the spare tyre is not showing as much sign of water damage (which is lower) so perhaps not a major leak - Any thoughts where the water could be coming in? tail light seals? I wonder if the back of the car has got wet from backing a boat trailer in too far???

And any thoughts on component F4kL would be much appreciated

Sorry about length of text

 

Just a quick note - can I put the rear SAM from the other car in (the other car is only 5 seats etc so no doubt it will have errors but will i damage car or the other SAM? assume trailer lights and fuel flap motor would still operate?

 

Hi @wannawagon ,

Did you ever resolve this issue around code 914B? I’ve been looking at the same code on a ‘06 GL500 and started a separate thread; link below. Any insights greatly appreciated!

Link to thread

kind regards

 

I gave up and have put in a multi port relay (relay for every function)

After doing this I was wondering if I should have been trying it on incandescent bulbed trailer but I already done the relay thing

I will go to thread