Engine Control System (Introduction): Overview Infiniti QX50 I

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DESCRIPTION

There are many operating conditions that lead to the malfunction of engine components. A good grasp of such conditions can make troubleshooting faster and more accurate.

In general, each customer feels differently about an incident. It is important to fully understand the symptoms or conditions for a customer complaint.

Utilize a diagnostic worksheet like the WORKSHEET SAMPLE below in order to organize all the information for troubleshooting.

Some conditions may cause the MIL to illuminate steady or blink and DTC to be detected. Examples

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1. Vehicle ran out of fuel, which caused the engine to misfire.
2. Fuel filler cap was left off or incorrectly screwed on, allowing fuel to evaporate into the atmosphere.

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1. INSPECTION START Check service records for any recent repairs that may indicate a related malfunction, or a current need for scheduled maintenance. Open engine hood and check the following: Harness connectors for improper connections Wiring harness for improper connections, pinches and cut Vacuum hoses for splits, kinks and improper connections Hoses and ducts for leaks Air cleaner clogging Gasket Confirm that electrical or mechanical loads are not applied. Headlamp switch is OFF. Air conditioner switch is OFF. Rear window defogger switch is OFF. Steering wheel is in the straight-ahead position, etc. Start engine and warm it up until engine coolant temperature indicator points the middle of gauge. Ensure engine stays below 1, 000 RPM. Run engine at about 2, 000 RPM for about 2 minutes under no load. Make sure that no DTC is displayed with CONSULT or GST. Are any DTCs detected? YES: GO TO 2. NO: GO TO 3 .
2. REPAIR OR REPLACE Repair or replace components as necessary according to corresponding Diagnosis Procedure. : GO TO 3
3. CHECK IDLE SPEED Run engine at about 2, 000 RPM for about 2 minutes under no load. Rev engine (2, 000 to 3, 000 RPM) two or three times under no load, then run engine at idle speed for about 1 minute. Check idle speed. For procedure, refer to " «IDLE SPEED: SPECIAL REPAIR REQUIREMENT»(ref-616999-S26947258422014052000000) ". For specification, refer to " «IDLE SPEED»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 10 . NO: GO TO 4.
4. PERFORM ACCELERATOR PEDAL RELEASED POSITION LEARNING Stop engine. Perform " «ACCELERATOR PEDAL RELEASED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S17738204502014052000000) ". : GO TO 5.
5. PERFORM THROTTLE VALVE CLOSED POSITION LEARNING Perform " «THROTTLE VALVE CLOSED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S07991613132014052000000) ". : GO TO 6.
6. PERFORM IDLE AIR VOLUME LEARNING Perform " «IDLE AIR VOLUME LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S34763962652014052000000) ". Is Idle Air Volume Learning carried out successfully? YES: GO TO 7. NO: Follow the instruction of Idle Air Volume Learning. Then GO TO 4 .
7. CHECK IDLE SPEED AGAIN Start engine and warm it up to normal operating temperature. Check idle speed. For procedure, refer to " «IDLE SPEED: SPECIAL REPAIR REQUIREMENT»(ref-616999-S26947258422014052000000) ". For specification, refer to " «IDLE SPEED»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 10 . NO: GO TO 8.
8. DETECT MALFUNCTIONING PART Check the Following. Check camshaft position sensor (PHASE) and circuit. Refer to " «COMPONENT INSPECTION»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Check crankshaft position sensor (POS) and circuit. Refer to " «COMPONENT INSPECTION»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 9. NO: Repair or replace. Then GO TO 4 .
9. CHECK ECM FUNCTION Substitute with a non-malfunctioning ECM to check ECM function. (ECM may be the cause of the incident, although this is rare.) Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs. Refer to " «ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM): SPECIAL REPAIR REQUIREMENT»(ref-616999-S26647245282014052000000) ". : GO TO 4 .
10. CHECK IGNITION TIMING Run engine at idle. Check ignition timing with a timing light. For procedure, refer to " «IGNITION TIMING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S13222141662014052000000) ". For specification, refer to " «IGNITION TIMING»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 19 . NO: GO TO 11.
11. PERFORM ACCELERATOR PEDAL RELEASED POSITION LEARNING Stop engine. Perform " «ACCELERATOR PEDAL RELEASED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S17738204502014052000000) ". : GO TO 12.
12. PERFORM THROTTLE VALVE CLOSED POSITION LEARNING Perform " «THROTTLE VALVE CLOSED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S07991613132014052000000) ". : GO TO 13.
13. PERFORM IDLE AIR VOLUME LEARNING Perform " «IDLE AIR VOLUME LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S34763962652014052000000) ". Is Idle Air Volume Learning carried out successfully? YES: GO TO 14. NO: Follow the instruction of Idle Air Volume Learning. Then GO TO 4 .
14. CHECK IDLE SPEED AGAIN Start engine and warm it up to normal operating temperature. Check idle speed. For procedure, refer to " «IDLE SPEED: SPECIAL REPAIR REQUIREMENT»(ref-616999-S26947258422014052000000) ". For specification, refer to " «IDLE SPEED»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 15. NO: GO TO 17 .
15. CHECK IGNITION TIMING AGAIN Run engine at idle. Check ignition timing with a timing light. For procedure, refer to " «IGNITION TIMING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S13222141662014052000000) ". For specification, refer to " «IGNITION TIMING»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 19 . NO: GO TO 16.
16. CHECK TIMING CHAIN INSTALLATION Check timing chain installation. Refer to " «REMOVAL AND INSTALLATION»(ref-616997-S32042697102014052000000) ". Is the inspection result normal? YES: GO TO 17. NO: Repair the timing chain installation. Then GO TO 4 .
17. DETECT MALFUNCTIONING PART Check the following. Check camshaft position sensor (PHASE) and circuit. Refer to " «COMPONENT INSPECTION»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Check crankshaft position sensor (POS) and circuit. Refer to " «COMPONENT INSPECTION»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: GO TO 18. NO: Repair or replace. Then GO TO 4 .
18. CHECK ECM FUNCTION Substitute with a non-malfunctioning ECM to check ECM function. (ECM may be the cause of the incident, although this is rare.) Perform initialization of IVIS (NATS) system and registration of all IVIS (NATS) ignition key IDs. Refer to " «ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM): SPECIAL REPAIR REQUIREMENT»(ref-616999-S26647245282014052000000) ". : GO TO 4 .
19. INSPECTION END If ECM is replaced during this BASIC INSPECTION procedure, go to " «ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM): SPECIAL REPAIR REQUIREMENT»(ref-616999-S26647245282014052000000) ". : INSPECTION END

ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM): Description

When replacing ECM, the following procedure must be performed. (For details, refer to " ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM): SPECIAL REPAIR REQUIREMENT ".)

PROGRAMMING OPERATION

Note. After replacing with a blank ECM, programming is required to write ECM information. Be sure to follow the procedure to perform the programming.

ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (VVEL CONTROL MODULE): Description

When replacing VVEL control module, the following procedure must be performed.

IDLE SPEED: Description

This describes how to check the idle speed. For the actual procedure, follow the instructions in "BASIC INSPECTION".

IGNITION TIMING: Description

This describes how to check the ignition timing. For the actual procedure, follow the instructions in "BASIC INSPECTION".

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1. CHECK IGNITION TIMING Attach timing light to loop wire as shown. Check ignition timing. : INSPECTION END

VIN REGISTRATION: Description

VIN Registration is an operation to registering VIN in ECM. It must be performed each time ECM is replaced.

Note. Accurate VIN which is registered in ECM may be required for Inspection & Maintenance (I/M).

ACCELERATOR PEDAL RELEASED POSITION LEARNING: Description

Accelerator Pedal Released Position Learning is a function of ECM 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 the harness connector of the accelerator pedal position sensor or ECM is disconnected.

THROTTLE VALVE CLOSED POSITION LEARNING: Description

Throttle Valve Closed Position Learning is a function of ECM 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 or electric throttle control actuator inside is cleaned.

IDLE AIR VOLUME LEARNING: Description

Idle Air Volume Learning is a function of ECM to learn the idle air volume that keeps engine idle speed within the specific range. It must be performed under the following conditions

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

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1. PRECONDITIONING Make sure that all of the following conditions are satisfied. Learning will be cancelled if any of the following conditions are missed for even a moment. Battery voltage: More than 12.9 V (At idle) Engine coolant temperature: 70 - 105°C (158 - 221°F) Selector lever: P or N Electric load switch: OFF (Air conditioner, headlamp, rear window defogger) On vehicles equipped with daytime light systems, if the parking brake is applied before the engine is started the headlamp will not be illuminated. Steering wheel: Neutral (Straight-ahead position) Vehicle speed: Stopped Transmission: Warmed-up With CONSULT: Drive vehicle until "ATF TEMP SE 1" in "DATA MONITOR" mode of "A/T" system indicates less than 0.9V. Without CONSULT: Drive vehicle for 10 minutes. Do you have CONSULT? YES: GO TO 2. NO: GO TO 3 .
2. PERFORM IDLE AIR VOLUME LEARNING With CONSULT Perform Accelerator Pedal Released Position Learning. Refer to " «ACCELERATOR PEDAL RELEASED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S17738204502014052000000) ". Perform Throttle Valve Closed Position Learning. " «THROTTLE VALVE CLOSED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S07991613132014052000000) ". Start engine and warm it up to normal operating temperature. Select "IDLE AIR VOL LEARN" in "WORK SUPPORT" mode. Touch "START" and wait 20 seconds. Is "CMPLT" displayed on CONSULT screen? YES: GO TO 4 . NO: GO TO 5 .
3. PERFORM IDLE AIR VOLUME LEARNING Without CONSULT NOTE: It is better to count the time accurately with a clock. It is impossible to switch the diagnostic mode when an accelerator pedal position sensor circuit has a malfunction. Perform Accelerator Pedal Released Position Learning. Refer to " «ACCELERATOR PEDAL RELEASED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S17738204502014052000000) ". Perform Throttle Valve Closed Position Learning. " «THROTTLE VALVE CLOSED POSITION LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S07991613132014052000000) ". Start engine and warm it up to normal operating temperature. Turn ignition switch OFF and wait at least 10 seconds. Confirm that accelerator pedal is fully released, turn ignition switch ON and wait 3 seconds. Repeat the following procedure quickly five times within 5 seconds. Fully depress the accelerator pedal. Fully release the accelerator pedal. Wait 7 seconds, fully depress the accelerator pedal for approx. 20 seconds until the MIL stops blinking and illuminates. Fully release the accelerator pedal within 3 seconds after the MIL illuminates. Start engine and let it idle. Wait 20 seconds. : GO TO 4.
4. CHECK IDLE SPEED AND IGNITION TIMING Start engine and warm it up to normal operating temperature. Let it idle for 20 seconds. Rev up the engine two or three times and make sure that idle speed and ignition timing are within the specifications. Refer to " «IDLE SPEED»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) " and " «IGNITION TIMING»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ". Is the inspection result normal? YES: INSPECTION END NO: GO TO 5.
5. DETECT MALFUNCTIONING PART-I Check the following Check that throttle valve is fully closed. Check PCV valve operation. Check that downstream of throttle valve is free from air leakage. Is the inspection result normal? YES: GO TO 6. NO: Repair or replace malfunctioning part.
6. DETECT MALFUNCTIONING PART-II Engine component parts and their installation condition are questionable. Check and eliminate the cause of the incident. It is useful to perform " «TROUBLE DIAGNOSIS - SPECIFICATION VALUE»(ref-616999-S32901675032014052000000) ". Refer to " «DESCRIPTION»(ref-616999-S10069631672014052000000) ". If any of the following conditions occur after the engine has started, eliminate the cause of the incident and perform Idle Air Volume Learning again: Engine stalls. Erroneous idle. : INSPECTION END

VVEL CONTROL SHAFT POSITION SENSOR ADJUSTMENT: Description

VVEL control shaft position sensor adjustment is an operation to adjust the initial position angle that is the basis for the VVEL control shaft position sensor.

It must be performed each time VVEL actuator sub assembly is replaced.

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1. START Do you have CONSULT? Do you have CONSULT? YES: GO TO 2. NO: GO TO 3 .
2. PERFORM VVEL CONTROL SHAFT POSITION SENSOR ADJUSTMENT With CONSULT Turn ignition switch ON. Select "VVEL POS SEN ADJ PREP" in "WORK SUPPORT" mode with CONSULT. Touch "Start" and wait a few seconds. Make sure the "CMPLT" is displayed on CONSULT screen. Select "VVEL POSITION SEN-B1" or "VVEL POSITION SEN-B2" in "DATA MONITOR" mode with CONSULT. Loosen the VVEL control shaft position sensor mounting bolt (1). Turn the VVEL control shaft position sensor (2) right and left while monitoring the output voltage of "VVEL POSITION SEN-B1" or "VVEL POSITION SEN-B2" and adjust the output voltage to be within the standard value. Voltage: 500 ± 48 mV Tighten the VVEL control shaft position sensor mounting bolt. Torque Value: 7.0 N.m (0.71 kg-m, 62 in-lb) Reconfirm that the output voltage of "VVEL POSITION SEN-B1" or "VVEL POSITION SEN-B2" is within the standard value. Voltage: 500 ± 48 mV NOTE: If it varies from the standard value after the bolt is tightened, perform steps 6 to 8 again. Turn ignition switch OFF and wait at least 10 seconds. Start engine and warm it up to normal operating temperature. Turn ignition switch OFF and wait at least 10 seconds. Perform idle air volume learning. Refer to " «IDLE AIR VOLUME LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S34763962652014052000000) ". : INSPECTION END
3. PERFORM VVEL CONTROL SHAFT POSITION SENSOR ADJUSTMENT Without CONSULT Disconnect VVEL control shaft position sensor harness connector. Remove VVEL actuator motor relay. Refer to " «COMPONENT PARTS LOCATION»(ref-616999-S16053064742014052000000) ". Turn ignition switch ON, wait at least 5 seconds and then turn OFF. Reconnect all harness connectors disconnected. Install VVEL actuator motor relay. Turn ignition switch ON and wait at least 5 seconds. Loosen the VVEL control shaft position sensor mounting bolt (1). Turn the VVEL control shaft position sensor (2) right and left while monitoring the output voltage between the VVEL control module terminals with a tester and adjust the output voltage to be within the standard value. VVEL control module Voltage Bank Connector + - Terminal Terminal 1 E14 3 4 500 ± 48 mV 2 5 6 Tighten the VVEL control shaft position sensor mounting bolt. Torque Value: 7.0 N.m (0.71 kg-m, 62 in-lb) Reconfirm that the output voltage of VVEL control shaft position sensor is within the standard value. VVEL control module Voltage Bank Connector + - Terminal Terminal 1 E14 3 4 500 ± 48 mV 2 5 6 NOTE: If it varies from the standard value after the bolt is tightened, perform steps 7 to 9 again. Turn ignition switch OFF and wait at least 10 seconds. Start engine and warm it up to normal operating temperature. Turn ignition switch OFF and wait at least 10 seconds. Perform idle air volume learning. Refer to " «IDLE AIR VOLUME LEARNING: SPECIAL REPAIR REQUIREMENT»(ref-616999-S34763962652014052000000) ". : INSPECTION END

MIXTURE RATIO SELF-LEARNING VALUE CLEAR: Description

This describes how to erase the mixture ratio self-learning value. For the actual procedure, follow the instructions in "Diagnosis Procedure".

System Description

ECM performs various controls such as fuel injection control and ignition timing control.

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Component Description

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The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the ECM memory. The program value is preset by engine operating conditions. These conditions are determined by input signals (for engine speed and intake air) from the crankshaft position sensor (POS), camshaft position sensor (PHASE) and the mass air flow sensor.

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Ignition order: 1 - 2 - 3 - 4 - 5 - 6

The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of the engine. The ignition timing data is stored in the ECM.

The ECM receives information such as the injection pulse width and camshaft position sensor (PHASE) signal. Computing this information, ignition signals are transmitted to the power transistor.

During the following conditions, the ignition timing is revised by the ECM according to the other data stored in the ECM.

1. At starting
2. During warm-up
3. At idle
4. At low battery voltage
5. During acceleration

The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition. The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.

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This system improves engine operation when the air conditioner is used.

Under the following conditions, the air conditioner is turned off.

1. When the accelerator pedal is fully depressed.
2. When cranking the engine.
3. At high engine speeds.
4. When the engine coolant temperature becomes excessively high.
5. When operating power steering during low engine speed or low vehicle speed.
6. When engine speed is excessively low.
7. When refrigerant pressure is excessively low or high.

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SET OPERATION

Press MAIN switch. (The CRUISE indicator in combination meter illuminates.)

When vehicle speed reaches a desired speed between approximately 40 km/h (25 MPH) and 144 km/h (89 MPH), press SET/COAST switch. (Then SET lamp in combination meter illuminates.)

ACCELERATE OPERATION

If the RESUME/ACCELERATE switch is pressed during cruise control driving, increase the vehicle speed until the switch is released or vehicle speed reaches maximum speed controlled by the system.

And then ASCD will maintain the new set speed.

CANCEL OPERATION

When any of following conditions exist, cruise operation will be canceled.

1. CANCEL switch is pressed
2. More than 2 switches at ASCD steering switch are pressed at the same time (Set speed will be cleared)
3. Brake pedal is depressed
4. Selector lever is in the N, P, R position
5. Vehicle speed decreased to 13 km/h (8 MPH) lower than the set speed
6. TCS system is operated

When the ECM detects any of the following conditions, the ECM will cancel the cruise operation and inform the driver by blinking indicator lamp.

1. Engine coolant temperature is slightly higher than the normal operating temperature, CRUISE lamp may blink slowly. When the engine coolant temperature decreases to the normal operating temperature, CRUISE lamp will stop blinking and the cruise operation will be able to work by pressing SET/COAST switch or RESUME/ACCELERATE switch.
2. Malfunction for some self-diagnoses regarding ASCD control: SET indicator will blink quickly.

If MAIN switch is turned to OFF while ASCD is activated, all of ASCD operations will be canceled and vehicle speed memory will be erased.

COAST OPERATION

When the SET/COAST switch is pressed during cruise control driving, decrease vehicle set speed until the switch is released. And then ASCD will maintain the new set speed.

RESUME OPERATION

When the RESUME/ACCELERATE switch is pressed after cancel operation other than pressing MAIN switch is performed, vehicle speed will return to last set speed. To resume vehicle set speed, vehicle condition must meet following conditions.

1. Brake pedal is released
2. A/T selector lever is in the P and N positions
3. Vehicle speed is greater than 40 km/h (25 MPH) and less than 144 km/h (89 MPH)

CAN (Controller Area Network) 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 transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.

Refer to " CAN COMMUNICATION CONTROL CIRCUIT ", about CAN communication for detail.

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ECM controls cooling fan speed corresponding to vehicle speed, engine coolant temperature, air conditioner ON signal, refrigerant pressure, target A/C evaporator temperature and A/C evaporator temperature.

Cooling fan control signal is sent to IPDM E/R from ECM by CAN communication line. Then, IPDM E/R sends ON/OFF pulse duty signal to cooling fan control module. Corresponding to this ON/OFF pulse duty signal, cooling fan control module gives cooling fan motor operating voltage to cooling fan motors. Cooling fan speed is controlled by duty cycle of cooling fan motor operating voltage sent from cooling fan control module.

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The fuel filler cap warning system alerts the driver to the prevention of the fuel filler being left uncapped and malfunction occurrences after refueling, by turning ON the fuel filler cap warning display on the combination meter.

ECM judges a refueled state, based on a fuel level signal transmitted from the combination meter.

When a very small leak is detected through the EVAP leak diagnosis performed after judging the refueled state, ECM transmits a fuel filler cap warning display signal (request for display ON) to the combination meter via CAN communication.

When receiving the signal, the combination meter turns ON the fuel filler cap warning display.

Reset Operation

The fuel filler cap warning lamp tunes OFF, according to any condition listed below

1. Reset operation is performed by operating the meter control switch on the combination meter. When the reset operation is performed, the combination meter transmits a fuel filler cap warning reset signal to ECM via CAN communication. ECM transmits a fuel filler cap warning display signal (request for display OFF) to the combination meter via CAN communication. When receiving the signal, the combination meter turns OFF the fuel filler cap warning display.
2. EVAP leak diagnosis result is normal.
3. Fuel refilled.
4. DTC erased by using CONSULT.

Note. MIL turns ON if a malfunction is detected in leak diagnosis results again at the trip after the fuel filler cap warning display turns ON/OFF.

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Diagnosis Description

This system is an on board diagnostic system that records exhaust emission-related diagnostic information and detects a sensors/actuator-related malfunction. A malfunction is indicated by the malfunction indicator lamp (MIL) and stored in ECU memory as a DTC. The diagnostic information can be obtained with the diagnostic tool (GST: Generic Scan Tool).

DIAGNOSIS DESCRIPTION: 1st Trip Detection Logic and Two Trip Detection Logic

When a malfunction is detected for the first time, 1st trip DTC and 1st trip Freeze Frame data are stored in the ECM memory. The MIL will not illuminate at this stage. < 1st trip >

If the same malfunction is detected again during the next drive, the DTC and Freeze Frame data are stored in the ECM memory, and the MIL illuminates. The MIL illuminates at the same time when the DTC is stored. < 2nd trip > The "trip" in the "Two Trip Detection Logic" means a driving mode in which self-diagnosis is performed during vehicle operation. Specific on board diagnostic items will cause the ECM to illuminate or blink the MIL, and store DTC and Freeze Frame data, even in the 1st trip, as shown below.

DIAGNOSIS DESCRIPTION: Driving Pattern

DIAGNOSIS DESCRIPTION: System Readiness Test (SRT) Code

System Readiness Test (SRT) code is specified in Service $01 of SAE J1979/ISO 15031-5.

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 information in this Service 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.

Note. 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.

Note. If permanent DTC is stored or MIL illuminates 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"), DTC (No DTCs) and permanent DTC (NO permanent DTCs) before the inspection.

DIAGNOSIS DESCRIPTION: Malfunction Indicator Lamp (MIL)

When emission-related ECU detects a malfunction in the emission control systems components and/or the powertrain control components (which affect vehicle emissions), it turns on/blinks MIL to inform the driver that a malfunction has been detected.

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1. The MIL illuminates when ignition switch is turned ON (engine is not running). NOTE: Check the MIL circuit if MIL does not illuminate. Refer to " «COMPONENT FUNCTION CHECK»(/infiniti/qx50/i-2013-2015/remont/testing-diagnostics/#engine-control-system-diagnostic-codes-symptom-tests) ".
2. When the engine is started, the MIL should go off. NOTE: If MIL continues to illuminate/blink, perform self-diagnoses and inspect/repair accordingly because an emission-related ECU has detected a malfunction in the emission control systems components and/or the powertrain control components (which affect vehicle emissions).

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

The SP value is used to detect malfunctions that may affect the Engine Control System, but will not illuminate the MIL.

The SP value will be displayed for the following three 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/B2 (The signal voltage of the mass air flow sensor)

See also:
• SYMPTOM TABLE