4.22.1 Description

The ECM performs a number of self checks on both the Random Access Memory (RAM), Read only Memory (ROM) and the two central processor units it uses to control the engine management system. A failure of any of the self-checks will require the ECM to be replaced.

The ROM is tested by performing continuous checksum calculations and comparing the results with a stored checksum value. If the calculated checksum and stored checksum do not match then a ROM failure is registered. The DTC logged will depend upon when the failure was identified.

A RAM test checks the RAM during ECM initialization and shut down.

The ECM continually monitors itself for illegal internal processor operations, tasks being performed in the wrong order and attempts to write to the RAM. If any of these faults are detected, P0606 will be logged.

The ECM uses two processors to perform its calculations, the two processors are continually communicating with each other to transfer critical information. Internal diagnostic hardware continuously monitors the communication between the two processors for errors. If the level of errors exceeds a defined limit then a failure is registered.