Circuit Deactivation Ignition Module (CDIM)

Vehicles equipped with a 6.4L engine may also be equipped with an extended idle shutdown system. The system is controlled by the PCM and uses several inputs to determine whether or not to shut the engine off. The function of the Circuit Deactivation Ignition Module (CDIM) is to disable the ignition circuits after the PCM has shut the engine off. For a complete description of the extended idle shutdown system and the related components, refer to Powertrain Control Software in the INTRODUCTION - GASOLINE ENGINES article or INTRODUCTION - 6.4L DIESEL ENGINES article.

Once the PCM has determined that the engine should be shut down, it sends a message to the Instrument Cluster (IC) along the High Speed Controller Area Network (HS-CAN) bus. The IC then sends a message to the CDIM along the Medium Speed Controller Area Network (MS-CAN) bus. Once the CDIM receives the message from the IC, the CDIM will begin a 60 second timer and monitor the MS-CAN bus for ignition switch position, brake pedal position and engine RPM. If the RPM remains at 0 and both the ignition switch and brake pedal switch remain undisturbed for 60 seconds, all CDIM internal relays will open and the vehicle will enter into the standard accessory delay. If 1 or more of the monitored signals changes during the 60 second time period, the CDIM internal relays will remain closed and allow voltage to remain applied to the ignition circuits.

To reactivate the CDIM and ignition circuits after the engine shuts down and the 60 second time elapses, the ignition key must be turned to the OFF position before attempting to start the engine or before the key is turned to any other position.

If the vehicle is getting the extended idle shut down system and the CDIM installed at a dealership as opposed to the assembly plant, the PCM must be enabled. To enable the PCM for extended idle shutdown, refer to the Extended Idle Shutdown Initialization General Procedure in ELECTRONIC ENGINE CONTROLS - DIESEL ENGINE article.