I'm getting heavy steering now and then.

Fine at idle but over 30mph it gets heavy. But not all the time. Started about a week or so ago. I flushed the fluid as it was rather black and burnt and replaced it with the green CHF. Could the servotronic valve be to blame?

could be that or the BCU

http://www.fullfatrr.com/forum/topic46792....onic+valve

Thanks Stan.

Are the symptoms the same with a dodgy BCU?

I've not code read yet so there might be something in there to point me in the right direction.

Search BCU on here. there is lots of info. It also sometime/often ties up with one of the doors not unlocking. Easy job to change for new. 1 hr tops.

That's unlikely to be the servotronic valve - it's effect is most at idle and reduces significantly at speed, but appears not to go to zero. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Isn't servotronic active all the time and dictates how much assistance to give based on speed? i.e less at speed gives more stability.

It's as though my steering forgets to go light again once it's gone stiff. I've not done conclusive tests but from recollection, switching off and on again fixes it. Then once back up to speed stays heavy once the speed drops. Not totally heavy as it's intermittent but definitely not right. Was fine a few weeks ago.

I'll have a read up on the BCU although i don't have any other electric issues.

Would disconnecting the servotronic valve multiplug effectively close it and give full PAS all the time? Would be a quick way to rule out anything else if so.

The Servotronic valve causes extra hydraulic assistance to be added over and above the steering rack base assistance.
At idle / very slow speed the bcu provides the maximum signal to the servotronic valve to generate max assistance.
As vehicle speed increases, the bcu output decreases, decreasing the servotronic assistance to minimal- but not zero.
The fact that you have the expected light steering at slow speed means the servotronic valve must be working ok and that the bcu is capable of providing the maximum output signal the servotronic valve needs.

I've got the opposite problem that at idle I'm not getting full assistance.
I 've got extra wiring installed to be able to monitor what the bcu is outputting and which also allows me to switch off the signal to the servotronic valve.
From what I've seen, even with the servotronic valve disabled, there is noticable power assistance - it feels slightly heavier at speed, but easily manageable.
With the servotronic valve disabled, the steering effort required at slow speed is significant. Manoeuvring is very difficult.

If your steering becomes very heavy at speed - ie heavier than the loss of the small amount of servotronic assistance, it might suggest something is wrong with the main hydrsulics - not bcu or servotronic. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Last edited by Pawl on 17th Sep 2018 9:00pm. Edited 1 time in total

Cheers Pawl.

I don't think the steering at speed is heavy. It feels normal as it used to before i had problems. Its when you slow down to take a corner that it sometimes catches me out. I expect it to be lighter than it is and have to put a bit of effort in or i'll keep going straight. lol

Maybe it is the BCU then - providing the correct output at very slow speed, but incorrect output intermittently at slightly higher speeds.
Unfortunately, swopping out the bcu is going to cost £200 to £300 + labour charges for fitting and programming.

Mine is Ok at speed, but not working correctly at very slow speed - a slightly different symptom, but probably same cause ! Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

I’m having the same issue. I checked codes and it said fuse b30 in BCU was gone. I’m going to investigate further on Sunday.
Incorrect tyre pressure seems to throw it out as well so check that first

Gonna get out there now with the computer and see if there's any codes.

Tyre pressures are fine. They were checked on Saturday.

I did notice this morning that whilst at idle, turning the wheel just a little drags the revs down as though there's a bit of struggle. Hadn't noticed that before.

Ran diagnostic.

No codes. Well i say no codes. There's one for the Gearbox selector switch which i know about (needs a new one) and there's one for ABS which needs a bit of poking round at.

Nothing for the power steering though.

You mentioned disconnecting the Servotronic valve in an earlier post. I forgot to say there's nothing to lose by trying that & seeing how the symptoms change - its all useful extra diagnostic info.

It's a shame the Gap IID tool can't actually read the BCU outputs & interpret whether it's working correctly.
I think it's only the full Land Rover diagnostic kit can do that.

Because the BCU output signal is PWM based, I don't think measuring it / interpreting it is easy for Gap to implement.
With the quantity of steering problems on Range Rovers it would be very useful though to help decide where the problem cause is & avoid replacing expensive items unnecessarily.

PS My car shows no related fault codes either ! Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

I'll disconnect the servotronic now and see what happens.

Is it a varying voltage that the bcu sends to the servotonic? Possible to measure with a bit of Heath Robinson and multimeter?

The BCU output is a Pulsed Width Modulated voltage & current - ie voltage that's be shut off & re-started at a varying frequency dependant on the vehicle speed.
At very low speed I think it's probably 100% on & at very high speed, it's mainly off.

I've measured mine crudely by adding some extra wiring and an extra connector between the Servotroniv valve & the main loom connector with a digital multi-meter at approx. 7.6V at zero / very low speed & I think 2 ish volts at high speed (can't remember that figure as not my focus). I can't remember if I was measuring AC or DC volts - both generate a reading.
I don't think you could measure it with analogue multi-meter as it wouldn't respond fast enough.

I'm not sure what the output at full assistance should be if working correctly. It's probably not 12V - as that wouldn't be OK for vehicles with flat / low batteries. More likely 10 or less Volts, but what ?????? Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk