EWS

EWS is the immobiliser system fitted to BMW models with M50 and M52 engines from 1994 onwards. Its basic function was to check that the doors were unlocked correctly and that the correctly-coded ignition key is being used. If it fails to detect the right signal, it will disable the ignition circuit, the injectors and the starter motor, which is a right pain if you're trying to do an M50 or M52 engine swap.

Components

• ECU
• EWS module
• Key
• Ignition Barrel Ring
• Send/Receive module (under the steering column)
• Loom

The ECU, EWSII and key come as a set. If you have the key and EWSII box, they can be reprogrammed to suit a different ECU by someone with the right equipment. So it is best to ensure you get all 3 components from the same car when purchasing, even see if there are spare keys to be had.

Wiring

To this end, here are the pictures to connect up the EWS system:

M50

M52

Disabling

If you really don't want the hassle of the EWS system, it is possible to deactivate it by swapping in a non-EWS chip into your ECU. However, depending on the loom you have, you may need to make some minor adjustments to the wiring. This technique is required for for OBD-I looms, which usually come with the 413 silver label ECU (as fitted to the E36).

Swapping the ECU is very simple, but on these older looms you need to cut one wire that leads to the ECU. Therefore, you will need to unclip the plug from the ECU and undo the small screw that holds the plug cover over the wires. With this removed, you will have the wiring exposed like this:

When looking at the wires, identify the very small numbers on the harness (circled in yellow) and find wire 56 at one end of the plug. Count over to the 66th wire, which should be a green wire but is sometimes black and purple. Cut this wire cleanly with wire cutters, then reassemble the plug and connect your replacement non-EWS ECU.

Reference

Learn more about the EWS system