Engine Starting Procedure
- All EWS 3.3 input requirements are met:
- System power and grounds provided
- Positive data exchange between the key and EWS control module (key accepted).
- BC code function is not active.
- Range selector in P or N (E38s and 540iA), or Clutch pedal depressed (540i Sport).
- EWS 3.3 control module closes the internal relay contacts providing the KL50 Start signal to the starter solenoid. Simultaneously, it calculates a stored code from the rolling code table and sends the calculated results to the ECM.
- On receipt of EWS's calculated results, ECM calculates it's own stored code and compares it's results with the received results from EWS.
- Results Identical: Engine Starts!
- Results not identical: ECM "rolls forward" to the next code in the rolling code table and calculates it. It continues to "roll forward" until it finds a match. If no match is found: Engine cranks but does not start!
The "forward roll" occurs up to a maximum of 200 times. This is necessary for the following reason. Example scenario: ECM is temporarily disconnected for service reasons. The ignition key is inadvertently switched on. When switched back off, the EWS is advanced one "rolling code" ahead of the ECM because the ECM was not connected. Once reconnected and the ignition key is turned to start, the ECM advances until a match is found. The rolling codes in each module are once again synchronized.
- When the ignition is switched off and no engine RPM signal is present in either the ECM and EWS, each module will automatically "roll forward" to the next pre-determined code (based on the code table.) This code is used for the next start sequence.