Specifications

Testing Testing Immobilizer (EWS) Systems

NOTE:

i Note the following regarding EWS II synchronization or alignment:

• The EWS II control module transmits the ISN to the DME continuously, whenever the ignition

is switched on. It must be matched by the DME for each successful engine start.

• EWS synchronization or alignment is currently not performed with the Snap-on

scan tool.

• After the ignition is switched off, the ISN is still transferred to the DME for 10 seconds, which

means that a vehicle with a possible EWS problem or faulty ignition switch key may start the

engine within that 10-second window. Always wait 10 seconds before starting the engine to

fully check the system.

EWS III

There are two different versions of EWS III. Version 3.2 is essentially the same as EWS II except

that the transmitter/receiver module is integrated with the EWS module. This system does not

have the rolling code security feature that was added for EWS III 3.3.

Version 3.3, used on EWS 3.3 has all the security features of EWS II. However, instead of using

an ISN jointly shared between the EWS and DME, EWS 3.3 uses a higher level of security called

“rolling code” technology. Rolling code technology uses a rolling code table permanently coded

into both the EWS and the DME which cannot be overwritten by any coding or flash programming.

With the ignition turned off, both the EWS and the DME automatically roll forward to the next code

on the code table. In case one gets out of sync, the other will roll forward up to a maximum of 200

times to establish synchronization. The rolling code is a one-way signal from the EWS to the DME.

The DME must perform its own calculation and match the EWS in order for the engine to start.

Replacement EWS 3.3 control modules are ordered VIN-specific and are delivered programmed

with the same rolling code table as the original module. Once ZCS coded, the rolling code needs

to be “reset” back to rolling code #1, providing synchronization of both modules.

Replacement DME control modules are blank and must be programmed for the specific vehicle.

After programming, the factory tool informs the EWS 3.3 control module that a new DME has been

installed. The next time the ignition is switched on, the EWS 3.3 module will send the entire rolling

code table to the DME and reset it to rolling code #1.

Table 4-23 EWS III applications

EWS III Version Series Year

Version 3.2

E38 1997

E39 9/97

Version 3.3

E38 5/97–1998

E39 9/97–1998

E46

All

E52

E53

E83

E85