Heavy Power Steering - PLEASE HELP

I have a problem with my 2007 TDV8 Vogue.

The power steering is heavier than it should be (and compared to my other TDV8 vogue). Had the car a month and issue has been there since I bought it (it was very cheap so couldn't say no).

Symptons:
Steering is heavy regardless of engine speed
Road speed seems to make no difference (although less noticiable at higher speed due to less sterring input required)
Very occasionally, the steering will be light after start up but not managed to link it to any other event that would cause it to go light
Sometimes when starting, the instrument cluster turns off for a split second and then goes through it's start up procedure when the engine is started. Not sure if this is related

Things Tried:
New servotronic valve
New BCU (or GEM as they are known on the 07MY).
Hours of internet forum searching.

I understand that on models up to 2007, the servotronic valve was controlled by the BCU and would open and close depending on a speed signal the BCU got from the ABS ECU. However reading the 2007MY workshop manual, the BCU has now been renamed the GEM (general electronics module) and the description of it's function makes no mention of the Servotronic valve. I was hoping to find some wiring diagrams to confirm that.

One other 'specialist' said the steering column joints may be stiff, but that doesn't explain why it would go light occasionally.

I'm unsure if the quirky instrument cluster is related or not, it could cause a CAN BUS fault, but on the 06MY the speed signal from the ABS ECU to the BCU was hardwired and did not use CANBUS, and the servotronic valve was hardwired to the BCU so cant see that would cause the issue. One person on the web fixed their instrument cluster with a new ignition switch (was only providing 9v output on the switched live during cranking hence the instrument cluster went down, cranking power to the engine was 12.6v).

I will check the ignition switch this weekend, but dont hold out hope of that fixing my steering issue.

Anyone have any ideas, or come across the issue before? There is a serious drink (or cash alternative) to anyone that comes up with the solution!!!!!

Thanks in advance

Neil

Have you tried raising both front wheels and turning the steering wheel to check for tight spots? maybe something is binding up, or it could even be the steering rack itself, the seals have been known to leak causing a drop in hydraulic pressure and heavy steering.

Not sure on the later models, but as you say the earlier ones used the BCU....I have not found wiring diagrams for the post 2005 model as yet...I will double check the workshop manual I have for the post 2007-2010 models but I don't think that has electrical information in it.

Hate to point a Newbie to another forum, but fullfatrr.com - Index are more clued up on the newer post 2007 models...

Saint.V8 said:

Have you tried raising both front wheels and turning the steering wheel to check for tight spots?

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No haven't tried that, but will do. I found reference to another owner who solved his problem by greasing the steering knuckle between the column and the rack. I didn't think this would be a problem but his steering would be light sometimes andf heavy at others so it's worth investigating.

As it's upstream of the rack, any stiffness would not be overcome by the rack as it only gets its input AFTER the knuckle.

Any other thoughts from anyone?

neiloakley said:

No haven't tried that, but will do. I found reference to another owner who solved his problem by greasing the steering knuckle between the column and the rack. I didn't think this would be a problem but his steering would be light sometimes andf heavy at others so it's worth investigating.

As it's upstream of the rack, any stiffness would not be overcome by the rack as it only gets its input AFTER the knuckle.

Any other thoughts from anyone?

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Yup, an introduction and location would not go amiss before you get some flak. :welcome2:

Diagnostics would be a good place to start, or you can keep chucking expensive parts at it.

Datatek said:

Diagnostics would be a good place to start, or you can keep chucking expensive parts at it.

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Thanks, but pretty obvious. If you can tell me 'how' to diagnose the problem then that would be useful. I've already checked for DTCC codes on all modules, checked for continuity between the BCU and servotronic valve (connector C0662, pins 9 and 11) and the speed wire from the ABS module (connector C0661, pin 23). I've also scoped the ABS signal versus the servotronic pulsed output. The output to the servotronic valve alternates from 0v to 4v when it should be 0v to 13v whilst stationary. The signal did not change with speed.

Going to check the ignition switch output now although I don't hold out any hope of that being the problem.

What diagnostic kit are you using? Ignition switch is a common fail item.

Datatek said:

What diagnostic kit are you using? Ignition switch is a common fail item.

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SnapOn Modis Ultra.

Ignition switch has 12v and auxiliary and ignition. These both drop to 7v when cranking, but the crank wire gets full 12v.

What usually fails with the ignition switch? How could it be linked to heavy steering?

Neil,

Has the PAS fluid been changed ??

No, but the problem is electrical. Scoping the GEM (known as BCU on pre07MY) shows the output to the servotronic valve drops when the steering is heavy. If power steering fluid was the problem then the GEM output would be proportional to the speed of the car

The only reason i ask, brother had 'similar.' Issues with his jag PAS, fluid change cured it...

Totally off topic question....

Are you the Neil Oakley who has a site about BMW Sat Navs etc...??? I ask as when you first posted a few days back the name sounded familiar, and it has just dawned on me I was searching for Nav update files for my 7'er and the L322 and a site bearing your name was at the top of the list.....

Just curious!

Yup that's me.

Plugged IDS into the car this morning and did pinpoint test on the BCU. Came up with a fault code P0083 cable tachometer A (speedometer) or instrument cluster signal is implausible.

But not sure if this is from me unplugging everything or what is actually causing the issue. Followed all the pin point tests and it suggested a new BCU but it's already had one!

Saint.V8 said:

Totally off topic question....

Are you the Neil Oakley who has a site about BMW Sat Navs etc...??? I ask as when you first posted a few days back the name sounded familiar, and it has just dawned on me I was searching for Nav update files for my 7'er and the L322 and a site bearing your name was at the top of the list.....

Just curious!

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Saint's only asking because you ran over his cat and now he knows how to find you

Think I solved it

Do I post the solution? Or don't i?

Used IDS to reflash the BCU back to AsBuilt spec. Then reflashed the module that contains the AsBuilt information based on all the modules the car had fitted, then flashed the BCU again.

Been fine for a week now, steering problem resolved at zero cost (time cost not included)

neiloakley said:

Think I solved it

Do I post the solution? Or don't i?

Used IDS to reflash the BCU back to AsBuilt spec. Then reflashed the module that contains the AsBuilt information based on all the modules the car had fitted, then flashed the BCU again.

Been fine for a week now, steering problem resolved at zero cost (time cost not included)

Click to expand...

Always post the solution or we will find you and destroy you!

Considering that was your 666th post, I believe you

neiloakley said:

Considering that was your 666th post, I believe you

Click to expand...

And Saint wants his cat back

Bad news I'm afraid. Problem has returned.

I swapped the suspect BCU for a good BCU from another Vogue of the same year and build and programmed it as required.

Even with the working BCU from another car, the steering has gone heavy again after a week of being fine. The car which received the suspect BCU is absolutely fine which essentially rules out the BCU being the problem.

So it's not BCU, battery, or the servotronic valve. Help!!!

Hi all,
Ancient thread, I know, but I'm having similar problems. Was this issue solved in the end, and what was the cure?
I've been scouring the web for information, but I've drawn a blank on anything conclusive.
Need help.

Cheers,
Henrik
'07 L322 tdv8