Our 3.6 TDV8 has an intermittent problem where the power steering assistance virtually disappears at slow speed when manoeuvring.
It's always OK first thing after a cold or hot engine start, but is typically non existent after suddenly slowing from any speed down to 1 or 2 mph.
From searching the forum, I've seen the BECM / BCU or Servotronic valve are most likely causes ( PAS fluid level is fine, fluid colour is OK & the pump makes no odd noises).

I've got a Gap-IID BT tool, but there are no faults identified & no other electrical issues elsewhere, so can anyone suggest how to diagnose what is the actual cause ?

I thought I read somewhere that you can check the electrical signals to the Servotronic valve, but I've not spotted any option for it in the Gap diagnostic menu.
Am I missing something or is there maybe a simple voltage or current check I can do on the relevant wiring connections ? Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

any good it is before yours but may help

L322 Range Rover: heavy steering
In November 2005, Land Rover issued technical bulletin LM211-006 for 2002-05 L322 Range Rover vehicles with VINs in the range 2A100047-5A198057. In these vehicles, abnormally high steering effort may be required during parking manoeuvres and diagnostic checks determine that the power steering control valve actuator in the steering gear is the cause. A service repair kit was developed so that the actuator could be replaced without needing to replace the entire steering gear assembly.

Sandyt,
thanks I did find that bulletin while trawling many forum posts.
I think that's the reason many RRs have their Servotronic valve changed.
It's cheaper to change than the BCU, but may not be the cause.
The bulletin refers to checking the relevant signals with the Land Rover Testbook diagnostic device.
Does anyone know if the Gap tool can do the same? Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

To complete this post in case it's found during a search for causes of heavy steering :
The heavy steering evolved after 6 months or so of non-action from an intermittent problem into a permanent problem.
Steering effort when stationary or at low speed was really heavy - to the point I gave up manoeuvring in car parks occasionally & left the car across 2 parking places. The only way to gain steering assistance at slow speed was to try & use the throttle to "blip" the engine speed.

After using a digital voltmeter on the electrical connections in between the BCU & steering rack Servotronic valve, I confirmed that the valve & the BCU were working OK - also wasted £100 replacing a fully functional Servotronic valve & £60 on a secondhand (temporary) replacement for our original BCU.
For info BCU voltage output to the Servotronic varies from around 7.5 volts stationary down to 2.5 volts at speed.

PAS fluid was changed together with a reservoir clean out with no effect on the heavy steering.
Hoses were all checked over for damage, swelling or any other defects - again with nothing found.

As a temporary minor improvement, I by-passed the BCU output & applied 12v direct to the servotronic valve - however, the improvement was only while moving at low - medium speed (ie when the effect of the servotronic valve would normally reduce).

Eventually - wary of a probable MOT failure - I decided to "bite the bullet" & create some pressure test equipment to check the pump performance by connecting between the PAS pump HP output & the HP pipe banjo.
LR specify test kit in the Workshop Manual, but I couldn't find anywhere selling anything similar, so ended up creating a kit by buying the individual parts (gauge, fittings, a couple of hoses & a HP shut off valve). I also bought a cheap S/H OE PAS pump to check the pipe connections before working on the car.
Use of the kit requires removal of the airbox, draining the PAS reservoir to permit removal of the PAS pump HP banjo connection & installation of the test kit connections.
Results of the test were significant !
The Pump should deliver more than 100bar at idle when the steering wheel is turned. I was only getting 20~ 30 bar - totally explaining the heavy steering / lack of assistance !
The pump output only climbed to 90bar at nearly 3000 rpm - also explaining why blipping the throttle / holding higher engine rpm would generate some assistance.
The pressure kit was then removed while I considered whether PAS pump replacement was an acceptable DIY job on the drive.

After more forum searching & discussion with j_rov, a local friend & forum member who'd had the unfortunate "pleasure" of changing his complete 3.6 TDV8 engine due to it digesting a broken EGR valve, the decision was that it was doable, but probably painful due to the rear pump retaining bolt not being easily accessible.
Forum comments also suggested that my second hand pump was probably OK - unless I was very unlucky - as internal failure was not very common across the many different vehicle applications using the same base ZF pump (Land Rover, VW Audi, Porsche, BMW etc).

Last week, with a good weather forecast, I tackled the pump removal & replacement (documented elsewhere as a new "How to "). I took much longer than the 3 hours suggested by 1 of the few people online I'd seen who'd tackled it as a DIY job Total time was 7 hours, but I was working very slowly due to the excess heat & excess tea breaks !

However, the result was great - I'd re-gained assistance at idle / stationary & the steering felt as the few good vehicles I'd driven (I'd bought the car with a known partial problem).

As side bonus', the engine appears slightly quieter / more refined - which I think maybe due to a few exhaust shield mounting studs I found without retaining nuts & sorted while doing the job.

Problem solved ! Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Good man, well done  2006MY 4.2 SC
BMW R1250 GSA Rallye TE
Triumph Tiger 1050 (sold)
1979 Pontiac Trans Am (sold)

Well done Paul. Got there in the end! __
2018 L405 3.0 TDV6 Vogue SE Fuji White
2000 4.6 V8 HSE Oxford Blue
1994 3.9 V8 Vogue Ardennes Green - resto project

Land Rover History:
2010 3.6 TDV8 Autobiography Stornoway Grey
2001 Discovery 2 TD5 GS
1999 Discovery 2 V8i XS
1994 Discovery 300Tdi
1993 Discovery 200Tdi
1989 Range Rover Vogue SE 3.5EFi
1976 Series 3 2.25
1977 Range Rover 2 door 3.5 Carb

Yes - only taken 18 months since buying the car - lol.
Many thanks for the guidance on access - without your pain first I might have put it off even longer ! Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Apologies for posting in an old thread but I am having similar issues.

Car in question is a 2010 Autobiography 3.6 TDV8.

I feel the steering in this one is heavier than my previous TDV8. It's not so heavy that the car is manoeuvreable when parking as yours was Pawl but it definitely isn't light/easy as one would expect of a Range Rover.

When I got the car I did discover a PAS fluid leak which turned out to be from the rack.

Dealer had a recon rack fitted which sorted the leak so hopefully this rules out the rack and the fluid as this was renewed along with the rack. (Correct cold climate fluid)

I like many others initially thought servotronic however i can see in SDD that the valve is being commanded open and the % value decreases with speed. If I unplug the servotronic then there is virtually no steering assistance.

I noticed tonight that if I rev the engine to 3k rpm and hold it whilst turning the wheels stationary the steering becomes lighter and more 'fluid' ?

Would this suggest pump as per your findings Pawl?

Many thanks

Unfortunately, your findings do seem to point at the pump being the problem - although your vehicle is 4 years younger than ours. Ours had done approx. 120,000miles when we bought it with the problem partially present.
How many miles does your vehicle have ?
You've proved its not likely to be the Servotronic valve or BCU / BECM if disconnecting the Servotronic removes most of the little assistance you have.
I think your post appears to suggest your heavy steering doesn't change on different occasions ie the heaviness is always present at low engine speed - again pointing towards permanent deterioration of something rather than intermittent operation of eg an electrical item.

You've now got to decide whether to invest some time & money in pressure testing to confirm its the pump rather than other items such as pipes / hoses. I think my test equipment cost approx. £80 for the hoses, valves, connectors & pressure gauge. The test took maybe a couple of hours from start, through removing air filter box, fitting the equipment, carrying out the test & removing the equipment.
If you've got a power steering specialist near you, you might be able to "buy" the test - but I'd imagine it will not be cheap due to the labour involved & the specialist wanting to pay for their equipment.

The alternative is to go straight to pump replacement, but if you pay someone to do it for you & the cost of a new pump & then don't solve the problem, you're going to be £400 ~£500 down (min,) & annoyed - lol. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Hi Pawl,

Thanks for your quick reply.

My car has done 116k miles. I did neglect to mention that sometimes the steering can be heavier or lighter than previous.

I good example was last night, it felt 'meaty' a bit like old BMW steering so I sat turning the wheels with the RPM raised to 3k and this seemed to help it lighten up.

I will see if I can find anyone fairly locally with suitable test equipment.. i'd rather waste £100 vs £400!

So mileage is similar to ours (You'd have to hope the pumps don't wear out any earlier).
Having taken my original pump apart after replacing it, I'm still none the wiser as to why output pressure was so low. The problem was permanent eventually, but was intermittent initially - like your's now .

I thinking testing first is sensible, even though it's increasing the overall cost of repair.
Otherwise, it's very easy to waste many hundreds of £ changing items that are not related to the actual cause of the problem.

Good luck ! Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Just been looking into this further and checking out your excellent how to Pawl.

I'm quite handy with the spanners so I reckon I might give pump replacement a go.

Trouble is I'm struggling to find a fairly priced pump to fit. New OE pumps are rediciously priced.

Don't suppose you came a across a source of remanufactured pumps before fitting the used one?

After re-searching the replacement pump, I did find a few people mentioning that ZF themselves sell alleged re-manufactured pumps.
Interestingly, there were also comments that some people believed that they were actually brand new - but ZF were trying to remove second hand pumps from the market to prevent less reputable suppliers using them to pass off as ZF pumps . As all the re-manufactured parts would be invisible inside the standard ZF housing, the customer would never know 1 - if anything had been changed or 2 - the quality of any changed parts. If true that they are brand new, even better !
It could possibly be true as the labour & part cost to strip down & replace the internals, then test the pump could be more expensive than the cost of a new pump straight off the production line.

I didn't actually get as far as identifying where you can buy new or re-manufactured ZF pumps as I decided that I was going to look for low mileage second hand first (as most RR vehicles appear to get to very high miles without having problems).

I just google searched for the relevant Land Rover part number for the pump & got lucky via eBay off a crashed car being broken by a breaker.
If it helps the part numbers are : Land Rover QVB500630 / ZF 7696 974 131
You can also see the date of pump manufacture on the sticker : 4/36/06 I believe means wk36 of 2006 (this is the pump off my car)

Hi Pawl,

Thanks again for your advice. I have decided to have a go at replacing the pump with a used one off ebay.

I am very interested to see if it makes any difference.

To try and give a better example of what I'm experiencing the steering isn't 'heavy' like non power assisted steering but it's certainly firmer than I'd expect for a Range Rover.

Slowing down from a 30mph main road to turn into my estate requires 2 hands, I could manage it with one but I have to work to overcome the resistance.

From what I remember of my previous TDV8 it could be driven with one hand if so desired.

How would you describe your steering feel with the new pump on Pawl?

With the replacement pump fitted, our car is back to what I'd expect - steering that's light enough to only need 1 finger to turn if moving slowly or that can be "palmed" around. As it should, it then firms up slightly as the speed increases - but never becomes heavy.
Before the pump change, it could get so heavy that both arms & shoulders would be working very hard to make tight turns while manoeuvring in car parks. Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk