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Chapter 4
Testing Immobilizer (EWS) Systems
8. The code is converted to a digital changing code and sent to the EWS control module.
9. If the code is valid, the EWS control module accepts the key as valid.
10. The EWS II activates the internal starter relay and the starter circuit is energized.
11. The EWS II sends the ISN code to the DME. If the ISN code matches the code stored in
the DME, the drive away protection is cancelled and the engine is allowed to start.
i
NOTE:
The data communication required for engine starting as described above takes place in
milliseconds—there is no noticeable delay during starting.
ä
IMPORTANT:
Starting problems caused by faulty ignition keys are common. Always have the owner bring in
all keys for use in diagnosing a no-start condition.
Once the identification and verification of the data codes are complete, the EWS II sends a
new changing code to the key for the next starting procedure. The changing code is a random
number that is generated by the EWS II control module. The transponder stores this code until
the next time the ignition is switched on.
The EWS II system is totally independent, in operation, from the mechanical key other than
the key fob which contains one of the components. The system features a wireless
communication link between a programmed EEPROM (transponder chip) housed in the
ignition key and the EWS II control module. The system will not allow the starter to engage
until a properly-coded transponder key is inserted into the ignition lock cylinder. The
transponder chip operates independently from the mechanical key blade and tumblers.
i
NOTE:
EWS II may have auto start recognition which disengages the starter motor as soon as the
engine is running.
Replacement of DME and EWS II Control Modules
Currently, replacement EWS control modules are ordered from the factory and come
pre-programmed to recognize the VIN specific key codes. After installing the EWS II control
module to the vehicle harness, it will need to be ZCS coded. If the original DME (ECM) was
previously replaced, the EWS II control module must be synchronized with the DME by
transferring the new DME ISN to the EWS II module. If the vehicle has the original DME and
the EWS module is replaced, then synchronization or alignment should not be necessary.
i
NOTE:
There is no limit to the number of times the ISN can be changed in the EWS II control module.
EWS II DME/EWS Synchronization or Alignment
If a factory-coded, replacement EWS II control module is ordered and the vehicle will not start,
if possible, check the service records if the original DME control module has been replaced.
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