ON-BOARD DIAGNOSTIC SYSTEM MALFUNCTION DETECTION FUNCTION [AJ (3.0L Duratec)]

Features

Malfunction Diagnosis Function

DTC Table

Comprehensive Component Monitor

• The Comprehensive Component Monitor (CCM) monitors for malfunctions in any powertrain electronic component or circuit that provides input or output signals to the PCM that can effect emissions and is not monitored by another system monitor. Inputs and outputs are, at a minimum, monitored for circuit continuity or specified range of values. Where feasible, inputs are also inspected for rationality, and outputs are inspected for proper functionality.

• 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 inspected continuously for opens, shorts, and unspecified values. Some digital inputs such as vehicle speed or crankshaft position rely on rationality inspections; inspecting if the input value makes sense at the current engine operating conditions. These types of tests require monitoring several components and can only be performed under appropriate test conditions.

• Outputs such as the IAC solenoid valve are inspected for opens and shorts by monitoring an inspection circuit or "dedicated IC chip" associated with the output. Other outputs, such as relays, require an additional inspection circuit to monitor the secondary side of the relay. Some outputs are also monitored for proper function by observing the reaction of emission-related components to a given change in the output command. An IAC solenoid valve can be functionally inspected by monitoring actual idle speed relative to the target engine speed. Some tests can only be performed under appropriate test conditions.

• The following is an example of some of the input and output components monitored by the CCM for OBD. The monitored components belong to a PCM supported subsystem.

- Includes: MAF sensor, IAT sensor, ECT sensor, TP sensor, CMP sensor, refrigerant pressure switch (medium pressure)

- Includes: Fuel pump, A/C relay, IAC solenoid valve, purge solenoid valve

• The CCM is activated after the engine is started and is operating. A DTC is stored in the PCM memory and the MIL is illuminated if a malfunction is detected for two consecutive drive cycles. Many of the CCM monitor items are also performed during self-test.

• The differential pressure feedback EGR system monitor is an on-board diagnostic function designed to test the integrity and flow characteristics of the EGR system. The monitor is activated after certain base engine conditions are satisfied and during EGR system operation. Signals from the following components are required for EGR monitor operation.

- ECT sensor, IAT sensor, TP sensor, CKP sensor

• The differential pressure feedback EGR sensor and circuit are continuously monitored for opens and shorts. The monitor inspects for input voltage from the differential pressure feedback EGR sensor that exceeds the maximum or minimum allowable limits. DTCs P1400 and P1401 are associated with this test.

• The EGR control valve and circuit are continuously monitored for opens and shorts. The monitor inspects if EGR control valve circuit voltage is inconsistent with the EGR control valve circuit control status. DTC P1409 is associated with this test.

• The test for a stuck open EGR valve or EGR flow at idle is continuously performed whenever at idle (TP sensor indicates closed throttle). The monitor compares the differential pressure feedback EGR circuit voltage at idle to the circuit voltage stored during key on engine off to determine if EGR flow is present at idle. DTC P0402 is associated with this test.

• The differential pressure feedback EGR sensor upstream hose is tested once per drive cycle for disconnection and plugging. The test is performed during acceleration with the EGR valve closed. The PCM momentarily commands the EGR valve closed. The monitor inspects if the differential pressure feedback EGR sensor voltage during diagnosis is inconsistent with voltage when there is no EGR flow. A voltage increase or decrease during acceleration while the EGR valve is closed may indicate a malfunction in the inspection hose during this test. DTC P1405 is associated with this test.

• The EGR flow rate test is performed when EGR control is in its most stable state (engine load and speed are moderate). The monitor compares the actual differential pressure feedback EGR sensor voltage to the ideal sensor voltage for that state to determine if EGR flow rate is acceptable or insufficient. This is a system test and may result in DTC P0401 (for any EGR system malfunction) to be stored. DTC P1408 is similar to P0401 but is detected during the KOER self-test.

• The MIL is illuminated if a malfunction is detected during two consecutive drive cycles.

• The fuel system monitor is an on-board function designed to monitor correction values for fuel injection control. The fuel control system uses fuel injection learning correction values stored in the PCM to compensate for deviations in fuel system components due to normal wear and aging. During fuel system feedback control, fuel injection control learns the corrections required to correct a "biased" rich or lean fuel system. These corrections are stored as fuel feedback correction coefficients. Fuel injection control has two correction methods: Long term and short term fuel corrections. Long term fuel correction uses the learning correction coefficient and short term fuel correction uses the fuel feedback correction coefficient. Inputs from the ECT, IAT, and MAF sensors are required to activate fuel injection control and perform fuel system monitor. Once activated, the fuel system monitor inspects if the fuel feedback and fuel learning correction coefficients exceed a specified limit. When a malfunction is detected as described below, the fuel system monitor stores a corresponding DTC.

- The HO2S detects the presence of oxygen in the exhaust gas and provides the PCM with feedback indicating the air/fuel ratio.

- A correction factor is added to the fuel injector pulse width calculation according to the long and short term fuel corrections as needed to compensate for deviations in the fuel system.

- As the deviation from the stoichiometric air/fuel ratio becomes larger, air/fuel ratio control suffers and uncombusted gas in the exhaust increase. If the stoichiometric air/fuel ratio exceeds the specified limit and the fuel correction coefficient approaches the specified limit, the fuel system monitor stores DTCs as follows:

• DTCs P0171 and P0174: Detection of a lean shift in fuel system operation

• DTCs P0172 and P0175: Detection of a rich shift in fuel system operation

• The MIL is illuminated if a malfunction is detected during two consecutive drive cycles.

• The HO2S monitor is an on-board diagnostic function designed to monitor the HO2S sensor for malfunctions or deterioration that can affect emissions. The HO2S used for fuel injector control is monitored for proper output voltage. Inputs from the ECT, IAT, MAF and CKP sensors are required for HO2S monitor operation. The fuel system and misfire detection monitors must also have been performed successfully before the HO2S monitor is activated.

- The HO2S detects the oxygen content in the exhaust gas and outputs voltage between 0-1.0 V. If the air fuel ratio is leaner than the stoichiometric air/fuel ratio (14.7: 1), the HO2S generates 0-0.45 V. If the air fuel ratio is richer than the stoichiometric air/fuel ratio (14.7: 1), the HO2S generates 0.45-1.0 V. The HO2S monitor evaluates the HO2S for proper operation.

- Once the HO2S monitor is activated, it monitors the HO2S output voltage and response frequency. Excessive voltage is determined by comparing HO2S output voltage with a specified maximum voltage. When the monitor conditions are satisfied, fuel injection control for HO2S monitor is executed and the HO2S output voltage and output response frequency are observed. At this time, the HO2S output voltage is evaluated to determine if the sensor is capable of switching (activated). An HO2S heater circuit malfunction is determined by turning the heater on/off and monitoring for corresponding voltage variation at the PCM terminal, and by measuring voltage flow through the heater circuit. DTCs associated with the HO2S monitor are divided in the following manner:

• P1130, P1131, P1132, P1150, P1151, P1152: Property failure

• P0133, P0153: Slow response rate

• P0135, P0155: Heater circuit malfunction

• The MIL is illuminated if a malfunction is detected during two consecutive drive cycles.

• The misfire detection monitor is an on-board diagnostic function designed to detect engine misfire and identify in which cylinder the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause. The misfire detection monitor will only be enable when certain base engine conditions are first satisfied. Inputs from the ECT, MAF and CKP sensors are required for the monitor to be performed. The misfire detection monitor is also activated during the self-test.

- The PCM synchronizes the ignition timing with crankshaft rotation signal from the CKP sensor. The crankshaft rotation signal is also the main signal used for determining which cylinder misfires.

- The crankshaft rotation signal generated by the CKP sensor is derived from by sensing the passage of teeth on the crankshaft position wheel mounted on the end of the crankshaft.

- This signal is input to the PCM and then used to calculate the time between crankshaft rotation signals, and also crankshaft rotation speed and acceleration. The power loss of each cylinder is determined by comparing the accelerations of each cylinder. When the power loss of a particular cylinder exceeds a specified value and other conditions are met, then that cylinder is determined to have misfired.

• Upon detection of a serious misfire that could cause catalyst damage, the MIL flashes once per second during the misfire and a DTC is stored.

• Upon detection of a misfire that could exceed the emission limits or cause the vehicle to fail an inspection and maintenance tailpipe emissions test, the MIL illuminates and a DTC is stored. DTC P0300 is stored in the case of a multiple cylinder misfire.

- DTCs P0301, P0302, P0303, P0304, P0305, and P0306 are stored in case of an individual type A or type B single cylinder misfire.

Freeze Frame Data

• When the PCM detects an engine control system malfunction. it stores the vehicle and engine operation status at that moment. This data stored in the PCM is freeze frame data.

• Freeze frame data is stored at the same time that the MIL illuminates and any previous DTC data is overwritten.

• Items stored as freeze frame data are shown below.

Freeze Frame Data Table

PID	Unit
Fuel feedback control status (RH,LH)	-
Charging efficiency (For engine control)	%
ECT	°C
Fuel feedback correction amount (RH, LH)	%
Fuel learning correction amount (RH, LH)	%
Intake air pressure	kPa
Engine speed	rpm
Vehicle speed	km/h

On-board Diagnostic System (OBD) Readiness Test

• Allows verification of whether or not the OBD items (monitor items) set in the PCM have been successfully completed.

• Fuel injection control, and CCM and non-CCM components, are constantly monitored since their status is constantly diagnosed.

• The status of intermittently monitored diagnostic items can be initiated by activating the initialization function for diagnostic data.

Self-test Function

KOEO (Key ON, Engine Off) Self-test

• The KOEO self-test, performed when the ignition switch is turned to the ON position and the engine is stopped, is designed to diagnose malfunctions related to DTCs applicable to this self-test function. A KOEO self-test begins when the connected WDS sends an execute command to the PCM.

KOER (Key ON, Engine Running) Self-test

• The KOER, self-test performed when the ignition switch is turned to the ON position, the vehicle is stopped and the engine is idling, is designed to diagnose malfunctions related to DTCs applicable to this self-test function. A KOER self-test begins when the connected WDS an execute command to the PCM.

Self-test Table