HDC Inactive!

[Wooden Horse]

This has just started to flash up, sometimes after 5 minutes and sometimes after 45 minutes. With the search down I would appreciate any advice. Doesn't seem to be any impact to normal running.

[camel_landy]

What car???

It could simply be that you're in the wrong gear but it works differently depending on the car.

M

[bogie]

could be anything...need to get diagnostics on it and it will say usually

when my old Range Rover did it, it was linked to a wheel speed sensor wire that had chafed through ...£20 later and a reset, all fixed

[Wooden Horse]

Thanks for the quick replies. It's an L322. I didn't want to take it straight ton a dealer without an idea of potential causes.

[camel_landy]

It will also be useful to know what model year and a bit of background as to what was happening at the time...

However, here are some pointers:

HDC is a SECONDARY system. You still use your engine & gearbox (engine braking) as your PRIMARY method of speed control. The system has a 'Target Speed' set in the ECU and when your speed goes over that target speed, it will pulse the brakes to bring it down.

HDC works in Reverse as well as forward gears but I can't remember exactly if your very early L322 has a limitation on which gears. At very least, it should work in R & 1 but probably 2.

So, that's how it works... This is what should make it inoperative (and how to make it operative again):

• Touching the brake (take foot off brake for it to operate again)
• Driving over 20mph (reduce speed).
• Putting the gearbox into Neutral (select a gear).
• Switching it off (turn it back on!).

If your HDC becomes inoperative outside of these scenarios, you might want to get it checked out.

M

[Wooden Horse]

camel_landy said:

It will also be useful to know what model year and a bit of background as to what was happening at the time...

However, here are some pointers:

HDC is a SECONDARY system. You still use your engine & gearbox (engine braking) as your PRIMARY method of speed control. The system has a 'Target Speed' set in the ECU and when your speed goes over that target speed, it will pulse the brakes to bring it down.

HDC works in Reverse as well as forward gears but I can't remember exactly if your very early L322 has a limitation on which gears. At very least, it should work in R & 1 but probably 2.

So, that's how it works... This is what should make it inoperative (and how to make it operative again):

• Touching the brake (take foot off brake for it to operate again)
• Driving over 20mph (reduce speed)
• Putting the gearbox into Neutral (select a gear).
• Switching it off (turn it back on!).

If your HDC becomes inoperative outside of these scenarios, you might want to get it checked out.


M

Thanks for the information. There isn't really a pattern to when it happens. It can come on a low speed or when is running at a steady speed e.g 60mph. The only thing that has changed recently is I have had four new tyres fitted, could this have dislodged a sensor?

It's a 2002 V8

Edited by Wooden Horse on Wednesday 30th January 20:34

[camel_landy]

Wooden Horse said:

Thanks for the information. There isn't really a pattern to when it happens. It can come on a low speed or when is running at a steady speed e.g 60mph. The only thing that has changed recently is I have had four new tyres fitted, could this have dislodged a sensor?

It's a 2002 V8

Hmmm... Dunno then.

As for the sensor, it's possible but IIRC it is the same sensor used for the ABS.

It's probably a dodgy bit of wiring somewhere so it might be easier to get it onto a diagnostics system.

M

[Lotusevoraboy]

Probably not the same but I had this on a disco. It was the brake light switch behind the brake pedal that triggered problems...shared wiring with HDc or summat.

[Wooden Horse]

Range Rovers, who would have one!