Immobilisation System

Immobilisation System
The ECM and the body control unit (BCU) security system comprise the immobilisation system.

The ECM and the BCU combine to prevent the engine from running unless the appropriate security criteria are met. The ECM and the BCU are a matched pair, if either one is replaced for any reason, the system will not operate unless the replaced unit is correctly matched to its original specification. TestBook must be used to reconfigure the immobilisation system.

Conditions
The ECM operates immobilisation in three states:
^ 'New'.
^ 'Secure'.
^ 'No Code'.

Function
With the ECM operating in the 'New' state, TestBook is required to instruct the ECM to learn the new BCU code. If the ECM is in delivery state (i.e. direct from the supplier), it will not run the vehicle and will store a new ECM fault code when it is fitted. This code must be cleared after instructing the ECM to learn the BCU code using TestBook.

When the ECM is in the 'Secure' state, no further action is required as the ECM has successfully learned the BCU code. A 'Secure' ECM can not be configured to a 'No Code' state.

If the vehicle is fitted with an ECM with a valid code, the engine will start and the MIL will go out.

However, if the ECM has an invalid BCU security code the engine will crank, start, and then immediately stall. The status of the security system can only be interrogated using TestBook.

TestBook is able to retrieve the following immobilisation fault codes: