Steering Column Fix - Torque Sensor (save £2000)

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Mike Le'mans
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Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 3:07 am

I've just spent the weekend ripping apart my steering column in order to fix the 611C fault code "steering column torque'.

I'd previously read that this was an issue that could only be remedied with a new/salvage steering column, because the torque sensor is buried deep within the column housings. But £2000 for a replacement column (+ labour !?) was a little steep for me, so I decided to take the thing apart to see what could be done. I took a few photos along the way, because I couldn't find anything on the web that had any disassembled column images, or any guides indicating what was required.

Before I start, here's a little bit of background to how I found myself looking at a £2000 bill for a replacement column.. I've steadily been fixing up a CAT-C write-off Z Coupe over the last few months, and had finally got it running only to find the power steering wasn't working at all. Checking the fault codes with my OBD reader showed me that this was a fault with the column torque sensor. A bit of internet research told me that the torque sensor wiring is connected to the car loom via a coil of wires that allow the column to move freely lock-to-lock, but not much more. To be honest, I was a little careless with the steering column while the steering rack was off the car, and can only assume that I'd spun the column around too many times and broken these small wires.

So here's some column removal instructions, and images to detail the internals / components of a later-model e86 steering column (any Z4 after 2006). Mines a RHD and from an automatic (but there shouldn't be much difference between any Z4 models).

1a) Move the drivers seat back as far as it goes. I'm 5'9" and working in the footwell was pretty uncomfortable. Moving the seat back is a must, but if you have more sympathy for your back, you may consider taking the seat out altogether.

1b) Disconnect the battery
2) Remove the airbag from the steering wheel (see other guides for this step).
3) Remove the steering wheel
4) Unclip the lower plastic shroud from around the indicator stalks. (theres a clip on either side, it's removed by pulling downwards).
5) Unscrew the upper plastic shroud (adjust the column tilt downwards, then unscrew the '+' head screw at the top).

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6) Unbold the indicator / wiper stalk unit (4 torx screws), carefully unclipping all cables.

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7) Begin removing the column itself. First, loosen the torx bolt holding the column to its universal joint in the engine bay, then slide the lower-steering joint out of the way.

8) Back in the car, remove the 8 main bolts (13mm hex head).

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9) Lower the column down as far as it will go at this point. There's a main wiring harness that will prevent it from coming out entirely. Rotate the column 90 degrees so that the motor hangs downwards. I've heard from a friend that it's possible to remove the column with the motor attached, but I couldn't see how this would be possible. So...

Disconnect the three plugs from the EPS module / motor, and one on the steering angle sensor (black box at the bottom end of the column).

Unbolt the power steering motor from the column (two torx bolts).

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10) Remove the column and motor, make yourself a cup of tea, and bring all your tools and parts inside to somewhere more comfortable.

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11). Lets start stripping down the column. Unbolt the hinge bolt at the lower end of the column. The bolt is in a snug plain bearing, so twist while pulling to extract it. I had to apply a little extra force with a g-clamp to get it started.

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12) Unclip the tension spring, then slide the whole top section (lock barrel etc) away from the main column.

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13) Unbolt the 3 torx screws that hold the upper column shroud to the centre section, and remove to reveal the torque sensor.

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14) Although you can now see the torque sensor, access to it is still pretty limited because its set back within the main central casting. So lets keep going...

15) Unpin and remove the steering angle sensor. In order to slide it all the way off the column, you'll need to remove the black plastic keyway from the end of the column (apparently a replacement comes as part of the steering angle sensor kit), and slide off the white plastic slieves that sit in the bulkhead bearing.

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16) Unbolt the three allen-head bolts that secure the lower casting from the centre casting. This joint is spring-loaded, to undo the bolts evenly, and support the casing as it is released.

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17) Unbolt the three small allen-head countersunk screws. These hold a plate at the reverse side of the roller bearing. I kept the bearing in place on the column ( i just removed the casing around it ), but if you need to change the bearing for some reason, you may want to keep these screws in place and press out the whole lot together).

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18) Using a hydraulic press or similar (I used some spring compressors and a bearing splitter), press the central casting off its bearing and away from the column shaft.

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19) You're now left with (as far as I can tell) the steering column as far as it can be dissembled. The torque sensor is crimped to the column at two sections (the torsion bar bit is somewhere between and underneath). I couldn't see how the plastic gear was attached, but assume this was some sort of interferance fit.

To fix my problem, I had to repair the internal coil wires within the torque sensor. There's about a metre of ribbon cable that wraps in a coil around the steering column to allow for lock-to-lock movement. In fact, there's probably enough wire to allow for 9 full wheel revolutions before it will break. Mine had broken right at the outside end, so I was able to un coil the wire from inside to give myself the room to fix it.


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20) Cut the coil wire back to a nice clean bit, and strip it ready to solder back on to the terminal. (there's a surprisingly large amount of wire to work with, not just 3 turns worth) i had to cut the plastic terminal housing back quite a lot with a scalpel in order to give myself 4 neat contacts to solder.

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21) Begin reassembly of the wiring back inside the torque sensor. I used some quick-setting two-part epoxy to secure the new connection in place, since none of the original plastic housing was being used in this fix.

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22) Reassembly is the opposite of disassembly!
Last edited by Mike Le'mans on Mon Dec 07, 2015 11:00 am, edited 1 time in total.

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by mj2k » Mon Dec 07, 2015 4:06 am

I have no technical skills,but this is a great write up. Amazing to see what is possible with said skills!
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Grumpyowl » Mon Dec 07, 2015 7:11 am

Congratulations on a great how to. :thumbsup:
I'm sure you'll save a lot of money for many people.

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by srhutch » Mon Dec 07, 2015 8:01 am

Great write up :thumbsup:

I presume you then turned the wheel a few turns in one direction to induce some slack in the ribbon, or was it in the correct position?
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Ewazix » Mon Dec 07, 2015 9:00 am

Nice work with a great write up! Probably the first I've seen of an complete EPS column tear-down :thumbsup:

The complexity and fragility of the column components you exposed might explain why there's no consistent cure for all the EPS issues people get. I'm not sure what was wrong with traditional hydraulic PAS really, it's good enough for an ///M?
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by GuidoK » Mon Dec 07, 2015 10:23 am

Interesting fix. The torque sensor fault is pretty rare I think. Has the car been in a crash?

Did you have to align (obd coding) the steering angle sensor again when you put it all back togheter?
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 10:36 am

srhutch wrote:I presume you then turned the wheel a few turns in one direction to induce some slack in the ribbon, or was it in the correct position?
yes, after refitting the ribbon cable I manually spun the column in my hands several turns either way to check where the safe 'middle' was, then kept the column still for the rest of the assembly. I had the steering lock on (key out of the barrel), so as soon as the top section goes back on it's all locked in place until it's back on the car. There's more play in the ribbon than I was expecting. This is the main reason for steering columns to be shipped with their locking pins in place, but in reality a full turn either way probably isn't going to do any harm (more than that and it gets more risky)!

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 10:48 am

Ewazix wrote:The complexity and fragility of the column components you exposed might explain why there's no consistent cure for all the EPS issues people get. I'm not sure what was wrong with traditional hydraulic PAS really, it's good enough for an ///M?
Agreed. My opinion is that IF BMW were to sell these components separately, it would mean that their dealership technicians would be expected to be able to replace them, and some of the components (torque sensor, EPS gear) aren't replaceable without drilling / heating the column.

I now think that aside from physical damage to the torque sensor (as in my case), or a worn out angle sensor (easy replacement without removing the column), all EPS issues are electrical / ECU based. The earlier cars appeared to suffer bearing wear and notchy steering - and on my column there'd be nothing at all stopping you from changing the bearings.

The argument that EPS saves weight seems nonsense. That electric motor weighs the same as any power steering pump I've seen. It must just be an emissions thing, because driving in a straight line for an emissions test won't draw any power at all on EPS, but mechanical would be draining something.

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 10:54 am

GuidoK wrote:Interesting fix. The torque sensor fault is pretty rare I think. Has the car been in a crash?
Yes, my car had a front-end crash. New chassis legs / turrets and everything in front of the engine has been replaced, but steering wasn't actually touched at all in the crash. I think I caused the damage myself by rotating the wheel too many times while the steering rack was off the car.
GuidoK wrote:Did you have to align (obd coding) the steering angle sensor again when you put it all back togheter?
Yes (getting it done today actually). I have error codes for 'steering angle plausability' and the ABS / DSC lights are on. A proper BMW specialist alignment and a recode of the SAS should cure all of that. There's no way to remove/replace the SAS without needing a recode from what I gather.

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by GuidoK » Mon Dec 07, 2015 12:29 pm

Mike Le'mans wrote:
GuidoK wrote: I think I caused the damage myself by rotating the wheel too many times while the steering rack was off the car.
Is your steering angle sensor still ok? that sometimes also has a ribbon cable inside.

I think aligning the steering angle sensor is an option in either INPA or DIS (or rheingold).

It is common to have to do that, I had to do that once on another car (a citroen, it also had a ribbon cable inside and some kind of rotary encoder, but that was a different setup (hydraulic ps)). Removing and repositioning the steering angle sensor always gives an dsc error as the ecu remembers the steering wheel alignment. (unless you fixate/lock both the wheels and the sensor.
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 4:04 pm

I had a look inside the SAS to make sure, it's free to move infinitely and uses four brushes on some sort of resistor plate. I haven't got a working INPA (do you need an old laptop for that?), but a local BMW specialist is doing it for £36 which seems reasonable.

The sensor itself seems ok, and is giving me angle readings - I guess these are just not the right ones!

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Last edited by Mike Le'mans on Mon Dec 07, 2015 7:06 pm, edited 1 time in total.

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by ekimj10 » Mon Dec 07, 2015 4:13 pm

Highly impressive write up and you have my full admiration in tackling a job like this.
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by Mike Le'mans » Mon Dec 07, 2015 7:03 pm

ekimj10 wrote:Is your other life an auto engineer?
Web developer... with 4 years of automotive engineering at uni. :D

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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by GuidoK » Mon Dec 07, 2015 7:16 pm

Mike Le'mans wrote:
The sensor itself seems ok, and is giving me angle readings - I guess these are just not the right ones!
Interesting that there seems to be no gearing system & rotary encoder to register what turn the steering wheel is in (lock to lock is more than 360 deg obviously). The sensor I took apart had that system too. It took me a while to figure out how that exactly worked. (the thing accidentally fell apart when I was dismanteling that column to get the dashboard out to fix something on the heating....)
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Re: Steering Column Fix - Torque Sensor (save £2000)

Post by andysat » Mon Dec 07, 2015 7:45 pm

As said great write up! :thumbsup:
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