This article show a step-by-step guide on how to removal and replace steering angle sensor for Mercedes Benz W204.
Step 1:Locate the negative terminal on the battery (yellow arrow) and remove the negative ground cable (red arrow).Place the cable in a manner that it cannot come in contact with the battery while working.Allow the car to sit for at least 15 minutes before working further on it to allow any remaining electrical energy in the car to dissipate.
Step 2:The steering wheel has a air bag that will need to be removed before the wheel can come off (red arrow)
Step 3:Use a T-27 and loosen both screws that hold the airbag unit on (red arrow).The screws are on each side of the back of the wheel at 3 and 9 o’clock.If the handle on your Torx driver is too long,try turning the wheel or even removing the lower dash cover to give you more room.
Step 4:In this photo you can see the T27 wrench that I removed from the holder to make it easier(red arrow).With both screws loosened you can pull the airbag forward away from the wheel(yellow arrow).
Step 5:Pull the airbag unit from the wheel and disconnect the plug (red arrows).Always store the airbag unit with the logo or padded side facing up.The two screws that hold the bag to the wheel will remain in the wheel(yellow arrow,one shown).
Step 6:The wiring connection for the horn and airbag does not disconnect from this point(yellow arrow).You will need to remove the wheel,ring and lower dash.Disconenct the two horn wires(red arrows).
Step 7:Use a 10mm Allen socket along with a breaker bar to loosen the single screw holding the wheel to the shaft (red arrow).Do NOT use the steering lock to help break the nut loose.Make sure to have someone hold the steering wheel stationary while breaking the bolt free.
Step 8:There are witness marks on both the steering whee(red arrows) and the shaft(yellow arrows) to make sure everything lines up when reassembling.If yours are faded make your own marks with some white out or nail polish.
Step 9:Pull the wheel straight back and off the shaft.The steering angle sensor will remain on the shaft.
Step 10:To remove the steering angle sensor use a Philips head screwdriver and remove the two small screws(red arrows).Use caution when pulling it off the steering shaft to remove it as one piece.If you separate the two plate the wiring will spool out and it is not easy to get it back in.
Step 11:You have to follow the wiring harness back down through the steering column cover to disconnect it(red arrow).
Step 12:The wiring connects up under the dash.You will nedd to remove the lower dash(red arrow) to get access to the connections.
Step 13:Remove the three Philips head screws holding the switches to the shaft(red arrows).This will give you more room to work around the wiring.
Step 14:The wiring connections for the steering angle sensor (red arrow) are up under the engine control unit(yellow arrow).You can remove the engine control unit by turning the release knob on it and pulling it out to give you more room to work.
This photo illustrates the two wiring connections for the sensor (red arrow) with the control unit removed.Disconnect the wiring.
Step 15:Feed the wiring up through the steering column cover and pull them out through the end.Installation is the reverse of removal.