Hi There, I have seen many posts on this HDC topic but not quite matching my situation. I have recently purchased a 2006 RRS in pristine condition with 137,000kms on the clock. When I have started the car I get the HDC System not Available message immediately for about 5 seconds and then it goes away. No other warning lights or bings or bongs and doesn’t come on during travelling. I have now replaced the battery based on reading a number of threads. The previous one was likely 7 to 10 years old but still coming up good on a battery test. After replacing the battery I still have exactly the same error. Should I be concerned? Any ideas what to look for now? There really are no other errors or faults. Thanks for any help or tips.

A blown brake light bulb has been known to cause HDC failure. This is because the brake lights are activated when HDC is actively controlling the brakes, so a lack of brake lights could cause an accident from a rear end shunt.

Does HDC work once the message has extinguished? Select HDC via the switch and drive along at 20km/h and take your foot off the accelerator pedal. HDC should then activate. If you try selecting one of the off road programs - try grass/gravel/snow for example - do you get a warning message saying "special programs not available"? You should do if HDC is still faulty. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Hi, thanks for your quick reply The HDC system seems to be available as normal once the error message has cleared. I have cycled through the off road programmes and all engage correctly.

The high level brake light may be the issue as it has an intermittent fault and does not always come on. I have checked the wiring which is all ok. I have a replacement brake light assembly coming this week, so let’s see if that fixes the problem I update here in the week. Cheers

Replacing the faulty/intermittent high level rear brake light has cured the HDC Fault that I was getting Thanks for the pointer RRSTDV8

Good news.

We do like a nice easy fix on here. They don't happen that often!  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed