Electronic
Column Lock
The BCM sends signal to the Electronic Column Lock by circuit 1603 and 1604. Depending if the motor needs to go forward or reverse the BCM sends grounds or 12 volts to the motor drive. I’m sure you have inversed the + or – on an electric motor to have it move from fwd to reversed, the BCM does exactly the same. The other wire is the switch (I would call it sensor) that sends the signal telling the BCM what is ECL pin state (engaged or retracted), circuit 1601. If the BCM does not get the appropriate signal (pin retracted: steering unlock), it cuts the fuel and engine stall when the C5 move around 2 mph.
What the recall does on 1997 1998 A4 :
They remove the steering wheel and all the components to get to the Steering Column Lock/Cam Orientation plate which is removed and replace by a new Cam Orientation Plate. The standard lock plate has 9 holes pattern to accept the ECL pin. The new lock plate is kind of a dummy one. It does not accept the ECL pin. The lock motor works, but pin is not engaging to the plate. This is why you ear it, but it does not lock the steering. That takes care of the steering locking problem.
The other part is to take care of the BCM cutting the fuel if it does not receive the appropriate signal from the ECL switch via circuit 1601. Here we go. They install a K harness (part 89023816). This harness bypasses the ECL switch. It has his own relay that sends the ground message to the BCM. Therefore, the BCM gets the message the column is not locked and does not cut the fuel. Similar to the cable sold by some other vendors.
A lot of the relays were found to be defective. There is the white and the black relay. If you want to make check the relay, check for ground on the green wire (circuit 1601) when ‘unlock’ or +12v when ‘Lock’. That green wire is the one that sends the Lock-unlock message to the BCM since its role is to bypass the original ECL switch signal.
If you do not get a ground signal or see +12v on green wire when you get the ‘pull key’ msg, that means the relay is not doing its job.
You can see on picture that you can easily probe the green and black wire from the back of the relay.
The 'pull key' message is there to resynchronize the ECL and the BCM.
That could also be the key pellet.
Here is a picture of the relay attached on the K-harness installed in the recall. On this, I'm testing if the relay is doing it's job as describe previously. Sorry, I had the camera in black and white.
