Comprehensive Component Monitor (CCM)
The CCM is an on-board strategy designed to monitor a fault in any electronic component or circuit that provides an input or output signal to the PCM and is not exclusively monitored by another monitor system. Inputs and outputs are considered inoperative when a failure exists due to a lack of circuit continuity, out-of-range value, or a failed rationality check.
The CCM covers many components and their circuits. The tests vary depending on the hardware, function, and type of signal. For example, analog inputs are typically checked for opens, shorts, out of range values, and rationality. This type of monitoring is carried out continuously. These tests may require the monitoring of several components and can only be carried out under the appropriate test conditions. Some outputs are also monitored for the correct function by observing the reaction of the control system to a given change in the output command. An example of this would be the injection control system.
In general, the CCM covers a broad range of individual component and circuit checks, and testing is carried out under various conditions. The CCM is enabled after the ignition switch is turned on for 3 seconds and the MIL is activated if the fault detected affects emissions. All of the CCM tests are also carried out during the on demand self-test.
The following is an example of some of the input and output components monitored by the CCM. The components monitored may belong to the engine, transmission, or any other PCM supported subsystem.
Inputs:
engine oil temperature (EOT), accelerator pedal position (APP), camshaft position (CMP)
Outputs:
injection pressure regulator (IPR), exhaust gas recirculation (EGR) valve
The MIL is activated after a fault is detected if the fault detected affects emissions.
Comprehensive Component Monitor
Misfire Detection Monitor
The misfire detection monitor is an on-board strategy designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as poor compression, fuel delivery, or mechanical engine failure. The misfire detection monitor is enabled only when certain base engine conditions are first satisfied. Input from the following sensors is required to enable the monitor: engine oil temperature (EOT), crankshaft position (CKP), mass fuel desired (MFDES), exhaust pressure (EP), intake air temperature (IAT), fuel level input (FLI) and injector control pressure (ICP).
The CKP signal generated is the main input used in determining cylinder misfire.
The input signal generated by the CKP sensor is derived by sensing the passage of the teeth from the crankshaft position wheel, which is mounted on the crankshaft.
The input signal to the PCM is then used to calculate the time between CKP edges and also crankshaft rotational velocity and acceleration. By comparing the accelerations of each cylinder event, the power loss of each cylinder is determined. When the power loss of a particular cylinder is sufficiently less than a calibrated value, and other criteria is met, the suspect cylinder is determined to have misfired.
Misfire Type B:
Upon detection of a misfire type B (1,000 revolutions), which exceeds the emissions threshold or causes a vehicle to fail an inspection and maintenance tailpipe emissions test, the MIL illuminates and a DTC is stored.
The DTC associated with multiple cylinder misfire is DTC P0300.
The DTCs associated with cylinder misfire are P0301, P0302, P0303, P0304, P0305, P0306, P0307, and P0308.
Diagnostic Trouble Codes (DTCs) DTC Description Possible Causes Diagnostic Aides
P0300 Random Misfire The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring. Oil/fuel aeration
Base engine
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P0301 - P0308 Misfire Detection Monitor The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder effected due to poor compression or any other cause. Base engine
Injector
If the MIL is on steady state due to a misfire, this indicates the threshold for emissions was exceeded.
Glow Plug Monitor (GPM)
The 6.0L diesel engine uses a GPM system designed to detect failed glow plugs or failed wiring in the glow plug system. DTCs indicate which cylinder has failed glow plugs or failed glow plug wiring.
The glow plug system is composed of a solid state glow plug control module (GPCM), glow plugs, and the associated wiring harness. The glow plug on-time is controlled by the PCM and is a function of oil temperature, barometric pressure, and battery voltage. The PCM enables the GPCM which powers the individual glow plugs. Glow plug on-time varies between 1 to 120 seconds. In addition to the PCM control, the GPCM limits the glow plug operation to 180 seconds regardless of the PCM commanded on-time. The power to the glow plugs is provided through the GPCM solid state drivers directly from the vehicle battery. The GPCM monitors and detects individual glow plug functionality, and the control and communication links to the PCM. The failures detected by the GPCM are passed to the PCM using a serial communication signal on the diagnostic line.
Note: Wait-to-start lamp on time is controlled by the PCM and is independent from GPCM on-time.
Glow Plug System
The key on engine off (KOEO) test is carried out in order to test the GPCM control circuit for failure. The glow plugs are not operated during this test.
The glow plug monitor self-test is a functional KOER test of the PCM carried out on demand with the engine running and the A/C off. The PCM activates the GPCM which monitors the glow plugs. The accelerator pedal may be used to increase the engine speed to increase voltage if needed. A fault must be present at the time of testing for the test to detect a fault. The DTCs are sent to the PCM on the diagnostic line and output to the diagnostic tool.
The following is an example of some of the input and output components monitored by the PCM. The components monitored belong to the engine system.
Inputs:
engine oil temperature (EOT), barometric pressure sensor (BARO)
Outputs:
GPCM
The MIL is activated after a fault if the fault detected affects emissions.