Hi guys,

car is showing a HDC system fault when being driven for anything over 10minutes.

Any ideas how serious this is? Range Rover Sport HSR
2.7 TDV6

Our cars for some reason tend to frequently throw up the HDC fault for reasons unrelated to any mechanical problem. The most frequent causes are low battery voltage, failed or non-OEM brake light bulbs or faulty brake light switch. Now the cold weather has started and we are switching on high drain systems such as seat and screen heaters putting demands on a battery that is going to less efficient at cold temperatures this does tend to show up a weak battery.

First thing to try is fully charging up the battery with a decent smart charger and monitoring the battery voltage simply by putting a voltmeter across the terminals when it has been sitting overnight. If there is something else causing the problem (such as a ABS or speed sensor) it should show up if you have the fault codes read with a good tool that can pick up Land Rover specific DTCs and not just a generic one that can only read engine fault codes. 2008 MY Java Black TDV8 HSE

Most common causes of HDC faults are........... Brake light bulbs and brake light swtches  2x TDV6. SE and HSE. Both returned to sender with issues👀
TDV8 Sport HSE...... Gone. Loved it but it didn't love me!!
Now rolling in MY10 Fullfat TDV8 Vogue. Slammed it to go round corners🙈
Cruising daily #56 mph in a Volvo V8. 😱
Lots of other toys in the cupboard...😜

It's no great surprise that blown brake bulbs cause HDC issues. The system is intimately linked to the brake system:

Quote:

When HDC is enabled, the ABS module calculates a target speed and compares this with the actual vehicle speed. The ABS module then operates the HCU, in the active braking mode, as required to achieve and maintain the target speed.
During active braking for HDC, the ABS module also energizes the HDC relay to operate the stop lamps

Quote:

To provide a safe transition from active braking to brakes off, the ABS module invokes a fade out strategy, which
gradually discontinues the braking effort, if it detects any of the following during active braking:

- HDC selected off with the HDC switch.
- Failure of a component used by HDC, but not critical to fade out function.
- Accelerator pedal pressed when transmission is in neutral.
- Brake overheat.

If fade out is invoked because of deselection or component failure, the HDC function is cancelled by the ABS module. If
fade out is invoked because the accelerator pedal is pressed with the transmission in neutral, or because of brake
overheat, the HDC function remains in standby and resumes operation when the accelerator pedal is released or the
brakes have cooled.

The fade out strategy increases the target speed, at a constant acceleration rate of 0.5 m/s2 (1.65 ft/s2), until the
maximum target speed is reached or until no active braking is required for 0.5 s. If the accelerator pedal is positioned
within the range that influences target speed, the acceleration rate is increased to 1.0 m/s2 (3.3 ft/s2).

When fade out is invoked because of component failure, a warning chime sounds and the HDC information indicator is
extinguished. The HDC warning indicator is illuminated (low line instrument cluster) or a message advising there is a fault
is displayed in the message center (high line instrument cluster).

When fade out is invoked because of brake overheat on vehicles with the high line instrument cluster, a message
advising that HDC is temporarily unavailable is displayed. On vehicles with the low line instrument cluster, the HDC
warning indicator flashes. At the end of fade out, the HDC information indicator flashes. The flashing indicators and/or
message continue while HDC remains selected until the brakes have cooled.

To monitor for brake overheat, the ABS module monitors the amount of braking activity and, from this, estimates the
temperature of each brake. If the estimated temperature of any brake exceeds a preset limit, the ABS module invokes the
fade out strategy. After the fade out cycle, the HDC function is re-enabled when the ABS module estimates that all of the
brake temperatures are at less than 64% of the temperature limit.

l2saqib wrote:

Hi guys,

car is showing a HDC system fault when being driven for anything over 10minutes.

Any ideas how serious this is?

My partner decided to change the wheels to some smart ones, he jacked my rrs 2006 up and changed the 2 rear ones and the passenger side wheel, he noticed they didn't fil and put the original ones back on. As e finished the jack gave way and it dropped and landed on the wheels. When I got in it and started it up that's when the hdc fault system unavailable special programmes off message came up on the dash then I got the traction control light, flashing amber park light, abs light and a couple of others I can put it at normal height but only if I repeatedly press the height rise button as I turn the ignition on bit as I drive the suspension lowering flashes up and it goes bk to normal height but is down on the drivers side especially on the back. I've replaced the speed sensor on the passenger side as the speedometer stopped working within about 20 mins of driving. I've lost my dsc button and hdc button as they stopped working as well but on the display screen on the 4x4 info its throwing up the hdc picture with an apostrophe in the middle of it but will show up the special programmes if the cars turned of for 5 mins or so and u just push the radio button to view the screen without starting it, but the special programmes disappears as soon as the key is turned to position 1. I've replaced the height sensor on the drivers side with a genuine Range Rover part. I've replaced all the tailgate bulbs also with genuine Range Rover bulbs. My local mechanic tried to re collaborate it but was unable to do so as it wouldn't let him. Taken the middle section out and checked all wires to the hdc and special programmes all of which were fine. I've been told it could be the body control module or the dynamique module somebody else said the compressor, the lights, the battery or a wire. I've also tried changing the brake light switch which had no effect. I've also tried resetting it by disconnecting the wires and touching them together, but still throwing up the faults. Could someone please help me? Also has anyone else been faced with the same problem, if so what was the cause? any ideas are welcomed as I don't know what to do. I have included some pics, as u can see the special programmes option is available without the vehicle being started and also pics of when it is started and also when it's in off road height. The back drivers side wheel does not seem in line to me and it's always moving on the screen whilst driving, and there seems to b a bigger gap between the orange line and white line, please can someone look at the pics and see if I'm missing anything. Also since throwing these faults up it seems to be drinking diesel bad ways and the mileage has stopped working. Also if you notice on the picture while the engines off the pic States lo while parked and turned off for 5 mins but will change to hi immediately when the key is turned to position 1. The hi/lo button still works.

As this seems to have happened after the car fell off the jack I would look there. Sounds like a damaged wiring loom pos caused by the jack.. I would have the loom checked out for damage.. 2008 G4 RRSport TDV8 current
2009 TDCi 90 current
2018 Discovery 5 HSE lux current
1994 Dakar current

Isn't one of the rear jacking point quite close to some suspension control?