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106 Posts
Discussion Starter #1
Happy Labor Day!

I did do some labor over this long weekend, not fun though.

Finally my 03 Range Rover is plagued by the notorious steering wheel lock failure. As I have an alternative vehicle (not any more a month later) and I don't really like the toggle switch solution, I decided to remove the steering column and disassemble the lock, the "unserviceable" lock.

1. Removing the steering column
I didn't remove the lower spindle with the steering column as suggested by RAVE; instead, I removed the nut and bold connecting the lower spindle to the upper spindle (near the steering angle sensor). This made the removal much easier, but I'm not sure if it'll make refitting easier, too.

There're four bolts fixing the the steering column body to the bracket. I found that the rear-left one (when you face the steering column) very difficult to remove, given that a lot of torque was required to initially loosen the bolt. I ended up with removing the left-hand-side "fascia end closing panel" (the small triangle cover --- you see it only when the door is open) and extended my arm into the fascia through the opening.

2. Breaking open the housing of the "unserviceable" lock
The steering wheel lock is "unserviceable" because the cover of the housing is secured on the housing by six metal pins, not removable screws. The only possible way to break open it is to destroy the pins --- although if you're lucky, you probably can reuse the pins.

I used general purpose 5/64" drill bit. First I drilled into the pin (it is hollow, like a miniature steel coil), and when I heard the noise of possible "engagement", I continued drilling into it slowly while withdrawing the drill outward. Then the pin was simply withdrawn while rotating. Repeated four times until I encountered the two pins hidden in the corners.

↑↑↑ Removed pin on the tip of the drill bit.

↑↑↑ This is the side facing the driver. Two upper holds are results of the removed pin.
However, the pin beneath the multiplug connector is very hard to reach.

To deal with that pin, I ended up with drilling a hole from the left side and forced the pin out from a perpendicular direction. It worked.
(By "left side" I mean left on the above picture; since the column is then placed on the table upside down, it's actually the right side if the column is on the vehicle.)

Now I removed five of the six pins, and as for the last one... just pulled the cover against that pin and then the cover came off, leaving that pin on the housing. Removed that pin with pliers.

3. Inside the lock housing...
↑↑↑ I rotated the picture so that the orientation now is as if you're looking at this lock from the right to the left when the column is on the vehicle. The left in the picture is actually rear.

The outermost of the housing, closest to the cover, is a circuit board, known as the "steering lock ECU". This ECU communicates with the immobilizer ECU through the black multiplug on the left, with the latch driving motor via the black-red-grey-black-red wiring harness on the bottom, and with the securing solenoid via the black harness on the top.

4. Separating the motor
By removing two white pins on both sides of the half cylinder I was able to remove the motor-circuit board together. The board is clipped onto the white motor housing by four clips.

The motor and its hall sensor are integrated into the white housing.

↑↑↑ Motor housing with upper housing opened, revealing the motor and the gear.

The motor drives a worm gear which turns the latch drive gear. On the other side (bottom, not pictured) the gear is reshaped as a cam, pushing the lock latch to release with the its heave.

On the gear there're also magnets. the hall sensor in the upper housing senses the position of the gear and demands the motor should stop when the fully locked/unlocked position is reached. I tested this: when the hall sensor is away, the motor along with the gear won't stop rotating (and it's fun).

↑↑↑ Hall sensor enclosed inside the housing.

5. A close look into the solenoid
↑↑↑ The securing solenoid in its de-energized, extended status

The securing solenoid is in place so as to prevent the released latch from engaging while the vehicle is in motion. It has its own hall sensor and tells the ECU if the pin is fully retracted or extended.

↑↑↑ Latch at its locked position.

↑↑↑ Latch at its unlocked position.

To unlock, the cam driven by the motor rotates and pushes the latch upward, releasing the lock, seen in the bigger hole. Meanwhile, the solenoid is de-energized, and the spring drives the pin to its extended length, blocking the smaller hole so that the latch won't come downward even if the motor fails.

To lock, the solenoid is energized and the pin retracts, exiting the smaller hole so that the latch can move downward, forced by its own spring. Luckily, a bad solenoid often doesn't retract, so the pin occupies the smaller hole, preventing the latch from lowering, thus not allowing the steering wheel to lock.

In another thread, our experts thoroughly analyzed the fashions in which the solenoid can fail.

6. Power on tests
With all connectors plugged back to place, I turned the key. As the key was close to position I, I heard very light noise from the solenoid repeating three times. The noise was very much like that comes from an engaging/disengaging relay, but even softer. When I put my fingers on the solenoid, I felt its vibration, so I knew that the solenoid was trying to do something, most possibly retracting the pin.

The motor didn't turn, as the hall sensor must hadn't told the ECU that the pin was in correct position.

Then I played with the solenoid. I pressed the pin to its retracted position, and the motor turned. The cam rotated a near 180 degrees, and if the latch were there, it would be lowered and the steering wheel would lock. Then, I turned key again, the motor turned in the opposite direction, and I released the solenoid. Again, I pressed, motor turned... Sometimes I couldn't make the timing right, but I did see response. This verified that the motor and its hall sensor were okay, the solenoid's hall sensor was okay, and the circuit board was okay. So the culprit was the solenoid.

7. Solutions? Not yet...
As rave stated in the above thread, the Kuhnke brand type HS7378/1 solenoid is a BMW-patented, Kuhnke-OEM component, so on Kuhnke's website you can't find it. It's neither sold by any retailer, possibly due to liability problems, and partially due to that they deem the steering wheel lock "unserviceable".

Then my thoughts are...
(1) No one retails this solenoid, really? Is there a "grey-market"?
(2) Now that BMW owns the design, is there any BMW models using this solenoid? Will it be on a part that's cheaper than $1000? If there're a few cheap (~$200-300) BMW parts containing this solenoid, maybe it's a good idea to buy one and swap the solenoid.


Premium Member
694 Posts
Does anyone know what the inside of the 2006 columns looks like? Specifically the locking mechanism? They are MUCH cheaper used, and don't appear to have this issue.

Very good write up by the way.

106 Posts
Discussion Starter #4
Does anyone know what the inside of the 2006 columns looks like? Specifically the locking mechanism? They are MUCH cheaper used, and don't appear to have this issue.

Very good write up by the way.
Well, I don't really think so... Although it wasn't until later 2007 when RR sold no longer had steering wheel lock mechanism, the 2006 MY is significantly different with 03-05 (in the UK 02-05). I believe they put a Jaguar engine inside, along with many other electronic devices, and the steering column lock might be one of them.

67 Posts
Fantastic findings: I have two inputs that may help with your solution.

1: If you want to maintain the full function of the lock: If you take all the current measurements of the solenoid (physical size, plunger stroke length, etc... there are a number of companies that may be able to combine sensors with their solenoid. It just won't be a drop in solution, and the harness, a new mount, sensor mounting (although many solenoids can be purchased with slots designed into the casing) etc... would have to be rebuilt.

2: Now for a cheaper outside the box option... I assume the ECU is looking for 5v signals from the High and Low position sensors within a certain time and sequence from both the solenoid position and the motor lock assembly position. Since you have this apart, perhaps you could measure the time delays between the key being turned and energizing this circuit to each sensor changing state. You could then replicate these 5V signals to the ECU using 4 time delay relays (assuming the ECU looks for the high and low positions of both the solenoid and the unlock motor) and permanently unlock the steering wheel by removing power from the solenoid plunger while the wheel is in the unlock position.

106 Posts
Discussion Starter #6
Thank you very much for your input!

For your first finding, I've been thinking about shipping my bad solenoid to some company in China, measuring the signals and sending the data to them as well, and having them reverse engineer the solenoid and build a bunch. Copyright? Well, I don't really think about reading books when I have no bread to eat...

For your second finding... first would you mind if I ask what do you do? You must be an electrical engineer, aren't you?:clap:

Honestly, I don't quite understand how the circuit works. But if you're interested in this project, we can cooperate: I give you as many photos as you want, or even videos, and you give me instructions what to measure. As for relays, I'm really not familiar with them, but I did have played with them when I repaired my fuel pump...
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