Comprehensive Component Monitor (CCM)

COMPREHENSIVE COMPONENT MONITOR (CCM)

The CCM monitors for concerns in any powertrain electronic component or circuit that provides input or output signals to the powertrain control module (PCM) that can affect emissions and is not monitored by another on board diagnostic (OBD) monitor. Inputs and outputs are, at a minimum, monitored for circuit continuity or correct range of values. Where feasible, inputs are checked for rationality, and outputs are also checked for correct functionality.

The CCM covers many components and circuits and tests them in various ways depending on the hardware, function, and type of signal. For example, analog inputs such as the cylinder head temperature (CHT) sensor or the intake air temperature (IAT) sensor are typically checked for opens, shorts, and out-of-range values. This type of monitoring is carried out continuously. Some digital inputs like crankshaft position or camshaft position rely on rationality checks to see if the input value makes sense at the current engine operating conditions. These types of tests may require monitoring several components and can be carried out only under appropriate test conditions.

Outputs such as the evaporative emission (EVAP) canister purge valve are checked for opens and shorts by monitoring a feedback circuit or smart driver associated with the output. Other outputs, such as relays, require additional feedback circuits to monitor the secondary side of the relay. Some outputs are also monitored for correct function by observing the reaction of the control system to a given change in the output command. Some tests can be carried out only under appropriate test conditions.

The following is an example of some of the input and output components monitored by the CCM. The components monitor may belong to the engine, ignition, air conditioning, or any other PCM supported subsystem.

1. Inputs:
Mass air flow (MAF) sensor, intake air temperature (IAT) sensor, cylinder head temperature (CHT) sensor, crankshaft position (CKP) sensor, camshaft position (CMP) sensor.
2. Outputs:
EVAP canister purge valve, canister vent (CV) solenoid, variable camshaft timing (VCT) solenoid.
3. The CCM is enabled after the engine starts and is running. A diagnostic trouble code (DTC) is stored in keep alive memory (KAM) and the malfunction indicator lamp (MIL) is illuminated after two drive cycles when a concern is detected. Many of the CCM tests are also carried out during the on-demand self-test.