Comprehensive Component Monitor (CCM)
Comprehensive Component Monitor (CCM)
The CCM monitors for malfunctions in any powertrain electronic component or circuit that provides input or output signals to the PCM that can affect emissions and is not monitored by another OBD monitor. Inputs and outputs are at a minimum~ monitored for circuit continuity or proper range of values. Where feasible inputs are also checked for rationality and outputs are also checked for proper 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 throttle position or engine coolant temperature are typically checked for opens shorts and out-of-range values. This type of monitoring is carried out continuously. Some digital inputs like brake switch or crankshafi position rely on rationality checks - checking 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 only be carried out under the appropriate test conditions.
Outputs such as coil drivers 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 proper function by observing the reaction of the control system to a given change in the output command. An idle air control solenoid can be functionally tested by monitoring the idle RPM relative to the target idle RPM. Some tests can only be carried out under the appropriate test conditions. For example the transmission shifi solenoids can only be tested when the PCM commands a shift.
The following is an example of some of the input and output components monitored by the CCM. The component monitor may belong to the engine ignition transmission air conditioning or any other PCM supported subsystem.
1. Inputs:
Air conditioning (A/C) pressure sensor camshafi position (CMP) sensor engine coolant temperature (ECT) sensor fuel tank pressure (FTP) sensor intake air temperature (IAT) sensor mass air flow (MAF) sensor throttle position (TP) sensor.
2. Outputs:
EVAP canister purge valve EVAP canister vent (CV) solenoid fuel pump (FP) idle air control (IAC) intake manifold runner control (IMkC) shifi solenoid (SS) torque converter clutch (TCC) solenoid wide open throttle A/C cutout (WAC).
3. CCM is enabled after the engine starts and is running. A DTC is stored in KAM and the MIL is illuminated afier 2 driving cycles when a malfunction is detected. Many of the CCM tests are also carried out during an on-demand self-test.