When the ignition is switched on, the PCM is supplied with voltage and switched on via the main relay.
Initially, the PCM checks all of the input signals for correct function, including those from the ECT, MAP and MAF (self-test).
Afterwards the key code is checked via the PATS system. If this is OK, the start release is issued to the system.
Note:
โข On the two-module system a voltage is present at the fuel injectors even if the start release has not been issued by the PATS system.
โข In a single-module system, there is no voltage present at the fuel injectors if the PATS system does not issue the start release.
After issuing the start release the PCM activates the IDM (via the IDM relay).
As soon as the IDM is supplied with voltage, it also checks all of the input signals, such as those from the CKP, CMP and KS, for correct function (self-test).
If the IDM completes the self-test without finding any faults, it sends an OK signal to the PCM via the CAN data bus.
The engine can now be started.
Note:
โข If the driver does not start the engine within a specified period of time (approximately 12 seconds), this is detected by the system as a fault and the engine does not start.
โข However, switching the ignition off and back on issues the system with another start release.