HDC flashing amber and restricted to 4th

This condition came out of the blue, 20 miles in to a 30 mile journey which I do every day. Flashing amber HDC light and restricted to 4th. Research suggests either a break heating problem or an auto shifter solenoid issue. Anyone able to throw any more light on it.

Thanks
barney

That's an interesting fault. I can't see why they would be related as there are two ECUs involved.
Maybe an earth fault?
Does the fault remain?

If both the vehicle speed sensor and the ABS speed signals fail, the auto's ECU will lock the gearbox in fourth gear as a fail safe mode.

Does the speedo go bonkers when this happens?
Do you get F then 4 flashing on the dash?

Hippo said:

If both the vehicle speed sensor and the ABS speed signals fail, the auto's ECU will lock the gearbox in fourth gear as a fail safe mode.

Does the speedo go bonkers when this happens?
Do you get F then 4 flashing on the dash?

Click to expand...

Makes perfect sense Hippo. The gearbox needs to know vehicle speed. I guess it takes it from the ABS wheel sensors.

Nodge68 said:

That's an interesting fault. I can't see why they would be related as there are two ECUs involved.
Maybe an earth fault?
Does the fault remain?

Click to expand...

No it's gone for now, I delved in to as much as I could find on it today and the previous reported instances of the exact same condition mostly relate to front brake overheating, which theoretically could reduce the effectiveness of the HDC system. Unfortunately I cannot think of any unusual driving conditions which would have caused an abnormal heating of the brakes. Thanks for getting back.

Barney

Hippo said:

If both the vehicle speed sensor and the ABS speed signals fail, the auto's ECU will lock the gearbox in fourth gear as a fail safe mode.

Does the speedo go bonkers when this happens?
Do you get F then 4 flashing on the dash?

Click to expand...

I did not notice the speedo going bonkers, but it did alternate F then 4.

Barney

This might just be worth something to you.

My brakes offside front has overheated today. Had a good look into it and found the piston pretty rusty
(Ordered 2 complete rebuild kits)

I've put this down to being much more apparent today because of the good weather.

P.s sliders where not good 2 weeks back either

Is it green?

There are no brake temperature monitoring systems fitted to the Freelander or any Land Rover as far as I know.
The HDC ECU simply runs an algorithm while the HDC is in operation. It is a rough guess at best. In reality the system cuts out much sooner than than it needs to. My own measurements show brake temperature well below the temperature the system thinks. I suspect this is to compensate for high ambient temps not seen in the UK.

rossymtb said:

This might just be worth something to you.

My brakes offside front has overheated today. Had a good look into it and found the piston pretty rusty
(Ordered 2 complete rebuild kits)

I've put this down to being much more apparent today because of the good weather.

P.s sliders where not good 2 weeks back either

Click to expand...

Thanks Rossy

Did you get any warning lights ?

Increase in the ambient temp was one of the things that crossed my mind whilst trying to establish some kind of "difference" I will take a look .

Thanks
Barney

Hippo said:

Is it green?

Click to expand...

amber

Not being green is good.

Rave talks about brakes over heating and a sticking throttle. I think the auto selecting limp mode is a reaction to the fault, as opposed to being the fault.

from rave disk:

ABS = yellow
ETC = yellow
HDC fail = yellow
HDC information = green

Wow these things are complex !!!

Looks like the last one is favourite, but it is it a fault or a sporadic condition that the ecu is throwing up a protection for and if it is what caused the condition.

Barney

It's difficult to answer. If you could get the codes read in the auto and abs this may offer a way forward. Other than that if it's an intermittent problem it will be difficult to track down without codes giving us a direction.

Has the Freelander returned to normal and driving ok now?

Some may wonder why I asked if it was green. I looked at a green one late last year with abs faults which also caused auto faults, even though the auto may have had faults of it's own. It was sold as the owner had to move. I thought it may have reappeared.