Engine Controls - Self-Diagnostics - M45: Overview Infiniti M45 II

Description

As part of an enhanced emissions test for Inspection & Maintenance (I/M), certain states require the status of SRT be used to indicate whether the ECM has completed self-diagnosis of major emission systems and components. Completion must be verified in order for the emissions inspection to proceed. If a vehicle is rejected for a State emissions inspection due to one or more SRT items indicating "INCMP", use the following information to set the SRT to "CMPLT". In most cases the ECM will automatically complete its self-diagnosis cycle during normal usage, and the SRT status will indicate "CMPLT" for each application system. Once set as "CMPLT", the SRT status remains "CMPLT" until the self-diagnosis memory is erased. Occasionally, certain portions of the self-diagnostic test may not be completed as a result of the customer's normal driving pattern; the SRT will indicate "INCMP" for these items.

The SRT will also indicate "INCMP" if the self-diagnosis memory is erased for any reason or if the ECM memory power supply is interrupted for several hours. If, during the state emissions inspection, the SRT indicates "CMPLT" for all test items, the inspector will continue with the emissions test. However, if the SRT indicates "INCMP" for one or more of the SRT, items the vehicle is returned to the customer untested.

If MIL is "ON" during the state emissions inspection, the vehicle is also returned to the customer untested even though the SRT indicates "CMPLT" for all test items. Therefore, it is important to check SRT ("CMPLT") and DTC (No DTCs) before the inspection.

Real Time Diagnosis In Data Monitor Mode Description (Recording Vehicle Data)

1. Automatic Trigger (AUTO TRIG) The malfunction will be identified on the CONSULT-II screen in real time. In other words, DTC/1st trip DTC and malfunction item will be displayed if the malfunction is detected by ECM. At the moment a malfunction is detected by ECM, "MONITOR" in "DATA MONITOR" screen is changed to "Recording Data... xx%" and the data after the malfunction detection is recorded. (Scheme 186) Then when the percentage reached 100%, "REAL-TIME DIAG" screen is displayed. If "STOP" is touched on the screen during "Recording Data... xx%", "REAL-TIME DIAG" screen is also displayed. The recording time after the malfunction detection and the recording speed can be changed by "TRIGGER POINT" and "Recording Speed". See CONSULT-II operation manual.
2. Manual Trigger (MANU TRIG) DTC/1st trip DTC and malfunction item will not be displayed automatically on CONSULT-II screen even though a malfunction is detected by ECM. DATA MONITOR can be performed continuously even though a malfunction is detected.

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Real Time Diagnosis In Data Monitor Mode Operation (Recording Vehicle Data)

1. Automatic Trigger (AUTO TRIG) While trying to detect the DTC/1st trip DTC by performing the "DTC Confirmation Procedure", be sure to select "DATA MONITOR (AUTO TRIG)" mode. You can confirm the malfunction at the moment it is detected.
2. While narrowing down the possible causes, CONSULT-II should be set in "DATA MONITOR (AUTO TRIG)" mode, especially in case the incident is intermittent. When you are inspecting the circuit by gently shaking (or twisting) the suspicious connectors, components and harness in the "DTC Confirmation Procedure", the moment a malfunction is found the DTC/ 1st trip DTC will be displayed.
3. Manual Trigger (MANU TRIG) If the malfunction is displayed as soon as "DATA MONITOR" is selected, reset CONSULT-II to "MANU TRIG". By selecting "MANU TRIG" you can monitor and store the data. The data can be utilized for further diagnosis, such as a comparison with the value for the normal operating condition.

The Specification (SP) value indicates the tolerance of the value that is displayed in "DATA MONITOR (SPEC)" mode of CONSULT-II during normal operation of the ECS. When the value in "DATA MONITOR (SPEC)" mode is within the SP value, the ECS is confirmed OK. When the value in "DATA MONITOR (SPEC)" mode is NOT within the SP value, the ECS may have one or more malfunctions.

The SP value is used to detect malfunctions that may affect the Engine Control System, but will not light the MIL. The SP value will be displayed for the following 3 items

1. B/FUEL SCHDL (The fuel injection pulse width programmed into ECM prior to any learned on board correction).
2. A/F ALPHA-B1/B2 (The mean value of air-fuel ratio feedback correction factor per cycle).
3. MAS A/F SE-B1 (The signal voltage of the MAF sensor).

Intermittent incidents may occur. In many cases, the malfunction resolves itself (the part or circuit function returns to normal without intervention). It is important to realize that the symptoms described in the customer's complaint often do not recur on (1st trip) DTC visits. Realize also that the most frequent cause of intermittent incidents occurrences is poor electrical connections. Because of this, the conditions under which the incident occurred may not be clear. Therefore, circuit checks made as part of the standard diagnostic procedure may not indicate the specific malfunctioning area.

Accelerator pedal released position learning is an operation to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time harness connector of accelerator pedal position sensor or ECM is disconnected.

Throttle valve closed position learning is an operation to learn the fully closed position of the throttle valve by monitoring the throttle position sensor output signal. It must be performed each time harness connector of electric throttle control actuator or ECM is disconnected.

Idle air volume learning is an operation to learn the idle air volume that keeps each engine within the specific range. It must be performed under any of the following conditions

1. Each time electric throttle control actuator or ECM is replaced.
2. Idle speed or ignition timing is out of specification.

CONNECTOR IDENTIFICATION

Note. For ECM pin voltage tests, see PIN VOLTAGE & PID VALUE CHARTS article.

Note. For connector and terminal identification not shown, see included circuit diagram/connector terminal identification within appropriate DTC testing procedure. See DIAGNOSTIC TESTS .

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System Description

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System Description & Operation

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Component Description

The Mass Airflow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.

The Mass Airflow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.

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For component description, see DTC P0112 & P0113 INTAKE AIR TEMPERATURE SENSOR .

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With the air/fuel mixture ratio self-learning control, the actual mixture can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the front Heated Oxygen Sensor (HO2S). The ECM calculates the necessary compensation to correct the offset between the actual and theoretical ratios.

When the amount of compensation is extremely large (the actual mixture is too lean), the ECM determines that the fuel injection system is malfunctioning and turns on the MIL (2-trip detection logic).

Component Description & Reference Data

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For Throttle Position (TP) sensor component description (Scheme 207)

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When a misfire occurs, engine speed will fluctuate (vary). If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor to vary, ECM can detect a misfire. The misfire detection logic consists of the following 2 conditions.

1. One Trip Detection Logic (3-Way Catalyst Damage) On the 1st trip that a misfire condition occurs that can damage the 3-way catalyst due to overheating, the MIL will blink. When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change. When the misfire condition decreases to a level that will not damage the catalyst, the MIL will turn off. If another misfire condition occurs that can damage the catalyst on a second trip, the MIL will blink. When the misfire condition decreases to a level that will not damage the catalyst, the MIL will remain on. If another misfire condition occurs that can damage the catalyst, the MIL will begin to blink again.
2. Two Trip Detection Logic (Exhaust Quality Deterioration) For misfire conditions that will not cause damage to the catalyst (but will affect vehicle emissions), the MIL will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1000 engine revolutions. A misfire malfunction can be detected on any one cylinder or on multiple cylinders.

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The Camshaft Position (CMP) sensor (PHASE) senses the protrusion of exhaust camshaft sprocket to identify a particular cylinder. The Crankshaft Position (CKP) sensor (POS) senses the piston position. When the crankshaft position sensor (POS) system becomes inoperative, the camshaft position sensor (PHASE) provides various controls of engine parts instead, utilizing timing of cylinder identification signals.

The sensor consists of a permanent magnet and Hall IC. When engine is running, the high and low parts of the teeth cause the gap with the sensor to change. The changing gap causes the magnetic field near the sensor to change. Due to the changing magnetic field, the voltage from the sensor changes.

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System & Component Description

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Description & On Board Diagnosis Logic

The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.

When the vehicle is parked, naturally the fuel level in the fuel tank is stable. It means that output signal of the fuel level sensor does not change. If ECM senses sloshing signal from the sensor, fuel level sensor malfunction is detected. For on board diagnosis logic (Scheme 215)

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The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.

Driving long distances naturally affects fuel gauge level. This diagnosis detects the fuel gauge malfunction of the gauge not moving even after a long distance has been driven. For on board diagnosis logic (Scheme 216)

Scheme 216

The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is mechanical float and the other is variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.

The vehicle speed signal is sent to the instrument cluster from the VDC/TCS/ABS control unit via the Controller Area Network (CAN) communication line. The instrument cluster then sends a signal to the ECM via the CAN communication line.

The ECM controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the electric throttle control actuator. The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM.

The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value memorized in the ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan operation, etc).

Description, On Board Diagnosis Logic & DTC Confirmation Procedure

For DTC description, on board diagnosis logic and DTC confirmation procedure (Scheme 217)

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Power Steering Pressure (PSP) sensor is installed to the power steering high-pressure tube and detects a power steering load. This sensor is a potentiometer which transforms the power steering load into output voltage, and emits the voltage signal to the ECM. The ECM controls the ETC actuator and adjusts the throttle valve opening angle to increase the engine speed and adjusts the idle speed for the increased load.

The ECM consists of a microcomputer and connector for signal input and output and for power supply.

Malfunction Indicator Lamp (MIL) is located on the instrument panel. When the ignition is turned on without engine running, MIL will light up. This is a bulb check. When the engine is started, MIL should go off. If MIL remains on, the on-board diagnostic system has detected an engine system malfunction.

Component Description, On Board Diagnosis Logic & DTC Confirmation Procedure

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Component Description, On Board Diagnosis Logic & Fail-Safe Mode

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Component Description, CONSULT-II Reference Value In Data Monitor Mode, On Board Diagnosis Logic & DTC Confirmation Procedure

For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and DTC confirmation procedure (Scheme 220)

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Component Description, Reference Data, On Board Diagnosis Logic & Fail-Safe Mode

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For component description, on board diagnosis logic and fail-safe mode (Scheme 222)

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Description, On Board Diagnosis Logic, Fail-Safe Mode & DTC Confirmation Procedure

For description, on board diagnosis logic, fail-safe mode and DTC confirmation procedure (Scheme 223)

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Component Description, CONSULT-II Reference Value In Data Monitor Mode, On Board Diagnosis Logic, Fail-Safe Mode & DTC Confirmation Procedure

For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic, fail-safe mode and DTC confirmation procedure (Scheme 224)

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Component Description, On Board Diagnosis Logic, Fail-Safe Mode & DTC Confirmation Procedure

For component description, on board diagnosis logic, fail-safe mode and DTC confirmation procedure (Scheme 225)

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For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and DTC confirmation procedure (Scheme 226)

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Component Description, CONSULT-II Reference Value In Data Monitor Mode & On Board Diagnosis Logic

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 228)

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 229)

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 230)

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Description, On Board Diagnosis Logic, DTC Confirmation Procedure & Diagnostic Procedure

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For description, on board diagnosis logic, DTC confirmation procedure, and diagnostic procedure (Scheme 232)

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System Description & Cooling Fan Speed Control

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 234)

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System Description, Component Description, CONSULT-II Reference Value In Data Monitor Mode & On Board Diagnosis Logic

For system description, component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 235)

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For component description, on board diagnosis logic and DTC confirmation procedure (Scheme 236)

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For component description, on board diagnosis logic and DTC confirmation procedure (Scheme 237)

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System Description, Component Description & CONSULT-II Reference Value In Data Monitor Mode

For system description, component description and CONSULT-II reference value in data monitor mode (Scheme 238)

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 239)

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For component description, CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 240)

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The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.

For system description and cooling fan speed control (Scheme 241)

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For component description CONSULT-II reference value in data monitor mode and on board diagnosis logic (Scheme 242)

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The vacuum cut valve and vacuum cut valve by-pass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister. The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve by-pass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve by-pass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then by-passed to apply intake manifold vacuum to the fuel tank. For component location and evaporative emission system diagram (Scheme 243)

Scheme 243

The vacuum cut valve and vacuum cut valve by-pass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister. The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve by-pass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve by-pass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then by-passed to apply intake manifold vacuum to the fuel tank. For component location and evaporative emission system diagram (Scheme 243)

When the gear position is "P" or "N", Park/Neutral Position (PNP) switch is on. The ECM detects switch position based on circuit continuity.

ECM receives 2 vehicle speed sensor signals via CAN communication line. One is sent from VDC/TCS/ABS control unit, and the other is from Transmission Control Module (TCM). ECM uses these 2 signals for engine control.

Brake switch signal is applied to the ECM through the stop lamp switch when the brake pedal is depressed. This signal is used mainly to decrease engine speed when vehicle is driving.

Component Description, CONSULT-II Reference Value In Data Monitor Mode, On Board Diagnosis Logic & Fail-Safe Mode

For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and fail-safe mode (Scheme 244)

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For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and fail-safe mode (Scheme 245)

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For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and fail-safe mode (Scheme 246)

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For component description, CONSULT-II reference value in data monitor mode, on board diagnosis logic and fail-safe mode (Scheme 247)

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Controller Area Network (CAN) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN H line, CAN L line) allowing a high rate of information to be transmitted with less wiring. Each control unit transmits/receives data but selectively reads required data only.