Thread: hill descent control (HDC) intermittent warning light issue

Just thinking out loud here as I have never had this particular issue, but had some similar.
Here is how I would approach this:
I suspect a short somewhere to earth, so I would start by disconnecting the wire that drives lamp, whether it be at the ECU plug or a switch somewhere (I would need to check RAVE to find out for sure, what initiates the lamp), then drive around normally for a couple of days to see if the lamp still comes on intermittently. If it does, you have a wiring problem. If not, probably a switch problem and back to the drawing board in this case, but at least you have ruled out most wiring and connector issues.

According to RAVE, HDC warning lamp alone indicates the Brake Lamps Relay is open or short circuit.

It doesn't effect function of any of ABS, ETC, HDC, or EBD. I would check out the brake lights.

Originally Posted by OffTrack

According to RAVE, HDC warning lamp alone indicates the Brake Lamps Relay is open or short circuit.

It doesn't effect function of any of ABS, ETC, HDC, or EBD. I would check out the brake lights.

one of the faults that came up was brake lamp relay open circuit!

awesome, thanks guys, I will have a look around for the break light relay and check it out.

Hi Geoff...my name is Scott and am hoping you can help me. I have identical problem...HDC warning light on intermittently, no other warning light(s) at all. I've replaced brake light bulbs, replaced brake light switch and put a new battery in...none of which have solved the problem. I've found no information anywhere about the location of the "Brake Light Relay" and saw your thread and thought you could tell me the physical location of that relay please. Thank you!

Hi. unfortunalely that relay is integral part of the interior fusebox, not simply removable cos it's soldered to the circuit board... i couldnt buy a very cheap fusebox to take it in pieces for that relay, i investigated about that some time ago but didnt get an answer and left it alone: Diagrams vs reality(mystery or am i dumb???) - Land Rover Zone , since then i've found the brake light relay too in the diagrams...it has the same feed but different outputs than the HDC relay ... it was long time ago but iirc it's the small one on the right side cos the big ones are for the wipers, the other one is a multicontact relay managed by the IDM, then there is a Brake lamp/light relay and the HDC relay which in some texts are the same in others not... but there are two other relays on the back too...it's a whole mess , i'll get to the end of it when my fusebox will fail then i'll replace it and take it in small pieces to find out i just took the covers off for those pictures but i didnt want to unsolder things cos the fusebox is good...the simplest cure is to replace the whole fusebox, or at least make sure there's no corrosion or water ingress there cos that's quite common...see the attachments

Hi Sierrafery,


Thank you very much for the photo uploads and information/links, I appreciate it. I have as of yet not had a chance to investigate fusebox (I just finished my project to get the cruise control to work) so my intermittent HDC warning only still exists.


An interesting correlation I've discovered if you have any thoughts/suggestions?


To this point, the HDC warning NEVER comes on if it's a cloudy day or the vehicle is not in direct sun light! Sounds too crazy to be coincidental...but I've had this random HDC warning light only issue for 2-3 months now and as time has gone by I came to the realization that when we were in the midst of the hot Summer months the warning light came on nearly ever single day. Never in the morning when it was cool and no direct sun light...always when the Disco sits out baking in the sun while I'm at work. It's almost like a sensor/something gets too hot from sitting out in the sun and the HDC warning comes on as soon as I start it.


So to summarize, never any other warning lights (and all warning lights do work, I check the lights at start-up)
Never comes on in the middle of a drive, always at start-up when it does feel like coming on.
And the kicker...NEVER comes on in cloudy weather or when the vehicle is parked out of direct sunlight.


Thanks!
-Scott

Hi, dry joints or bad contacts are sensitive to heat maybe that's why