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Infiniti G20 1991 - 1991 ENGINE PERFORMANCE Self-Diagnostics - G20
Infiniti G20 1991 - INTRODUCTION
If no faults were found while performing BASIC TESTING , proceed with ENTERING SELF-DIAGNOSTICS. If no fault codes or only pass codes are present, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.).
Infiniti G20 1991 - SELF-DIAGNOSTIC SYSTEM
The self-diagnostic system is used for diagnosing malfunctions of Electronic Concentrated Control System (ECCS) sensors and actuators. The Electronic Control Unit (ECU) has 2 available diagnostic modes. Before entering self-diagnostics, perform BASIC TESTING . This eliminates wasted diagnostic time and invalid diagnostic results.
NOTE: When performing BASIC TESTING , be careful not to erase any diagnostic information stored in ECU memory.
Infiniti G20 1991 - HARD FAILURES
Hard failures will cause CHECK ENGINE light to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control unit will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.
Infiniti G20 1991 - INTERMITTENT FAILURES
Intermittent failures may cause CHECK ENGINE light to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be stored in ECU memory. Not all trouble codes will illuminate CHECK ENGINE light. If related fault does not reoccur within a certain time frame, related trouble code will be erased from ECU memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
NOTE: Follow proper diagnostic routine when diagnosing the system. See DIAGNOSTIC ROUTINE table.
Infiniti G20 1991 DIAGNOSTIC ROUTINE
Procedure Order Basic Diagnostic Procedures 1st Entering Diagnostics 2nd Retrieving Trouble Codes 3rd Symptoms (1) 4th Intermittents (1) 5th
(1) Symptoms and intermittents are covered in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
Infiniti G20 1991 - CHECK ENGINE LIGHT
NOTE: All trouble codes do not activate CHECK ENGINE LIGHT.
All models are equipped with a CHECK ENGINE light. As a bulb check, light will illuminate when the ignition is turned on and engine is not running.
On California models, CHECK ENGINE light illuminates when a fault is detected with engine running. A corresponding trouble code will set in ECU memory. CHECK ENGINE light also illuminates if ECU or crank angle sensor malfunctions.
On Federal models, CHECK ENGINE light illuminates only when ECU or crank angle sensor malfunctions with engine running.
Infiniti G20 1991 - DIAGNOSTIC MODES
The self-diagnostic system can detect ECCS malfunctions and store related trouble code. Intermittent codes are also stored. All codes are stored until cleared from memory. If an intermittent does not reoccur within 50 ignition key cycles, it will be cleared from memory.
Switching modes is not possible when the engine is running. During diagnosis, the self-diagnostic system will automatically return to Mode I from Mode II when the ignition switch is turned off.
Infiniti G20 1991 - Mode I
This is normal operating mode. In this mode, the CHECK ENGINE light and Red Light Emitting Diode (LED) inspection light in ECU stay on when the ignition is turned on, engine off (bulb check). If the engine is started, CHECK ENGINE light and Red LED in ECU should turn off, unless a fault or trouble code is present (Calif. models) or if the ECU or crank angle sensor is malfunctioning (Calif. and Fed. models).
Infiniti G20 1991 - Mode II
This is self-diagnostic mode for retrieving fault or trouble code(s). See RETRIEVING CODES. With the engine running, Mode II can monitor air/fuel mixture feedback control. The CHECK ENGINE light and Red LED in the ECU will flash on (lean) and off (rich) more than 5 times every 10 seconds with engine speed at 2000 RPM when system is in closed loop. The CHECK ENGINE light and Red LED do not flash remain on or off if system is in open loop.
Infiniti G20 1991 - ECU LOCATION
The ECU is located under dash, behind center console.
Infiniti G20 1991 - ENTERING SELF-DIAGNOSTICS
- Turn ignition on, but leave engine off. Using a small screwdriver, turn diagnostic mode selector on ECU fully clockwise. Wait at least 2 seconds and then turn diagnostic mode selector fully counterclockwise. Mode II self-diagnostic will result and the CHECK ENGINE light and the Red LED inspection light will flash trouble codes (if present).
- If engine is started at this stage, the CHECK ENGINE light and the Red LED inspection light will display the condition of the air/fuel mixture which is monitored by the O2 sensor or if the system is in closed or open loop.
Infiniti G20 1991 - RETRIEVING CODES
NOTE: Mode II can retrieve trouble code(s) from self-diagnostic system.
Read trouble codes with either CHECK ENGINE light or Red LED inspection light on ECU. Trouble codes will flash after selecting Mode II.
Trouble codes are indicated by the number of flashes from CHECK ENGINE light or Red LED inspection light. Count the flashes. For example, 3 long (.6 second) flashes followed by 2 short (.3 second) flashes of CHECK ENGINE light or Red LED indicate a Code 32.
Infiniti G20 1991 TROUBLE CODE IDENTIFICATION
Code System Affected Probable Cause 11 (1) Crank Angle Sensor (2) No crank signal 12 Airflow Meter Circuit Open/shorted circuit 13 Coolant Temp. Sensor Open/shorted circuit 14 Vehicle Speed Sensor (VSS) No VSS signal 21 (1) Ign. Signal Circuit (2) Open/shorted circuit 31 ECU Signals not normal 32 EGR Function (Calif.) No EGR action 33 O2 Sensor Open ckt/high O2 signal 34 (1) Knock Sensor Open/shorted ckt 35 Exhaust Temp. Sensor (Calif.) Open/shorted ckt 43 Throttle Sensor Open/shorted ckt 45 Injector Leak (Calif.) Leak at injector(s)
(1) These trouble code(s) not will activate CHECK ENGINE light.
(2) Check items causing a malfunction of crank angle sensor circuit first, if Codes 11 and 21 are present at same time.
Infiniti G20 1991 - CLEARING CODES
NOTE: Ensure all diagnostic codes are accessed from ECU memory before disconnecting battery or switching from Mode II to Mode I.
Infiniti G20 1991 - Memory Erase
Stored memory can be erased by disconnecting battery or selecting Mode I after Mode II has been accessed.
Fig. 1: Infiniti G20 1991 - Component Locations - Identifying Trouble Code Chart Symbols
Infiniti G20 1991 - CODE CHARTS
NOTE: Most code charts shown include procedures using Nissan's CONSULT TESTER. If CONSULT TESTER (J-38465) is not available, disregard steps using CONSULT tester and use alternate test procedure. (OK = Okay, NG = No Good).
Infiniti G20 1991 - CODE 11: CRANK ANGLE SENSOR
Fig. 2: Infiniti G20 1991 - Component Locations - Code 11: Crank Angle Sensor Circuit Diagram
Fig. 3: Infiniti G20 1991 - Component Locations - Code 11: Crank Angle Sensor & ECU Harness Location
Fig. 4: Infiniti G20 1991 - Component Locations - Code 11: Crank Angle Sensor Flow Chart (1 of 2)
Fig. 5: Infiniti G20 1991 - Component Locations - Code 11: Crank Angle Sensor Flow Chart (2 of 2)
Infiniti G20 1991 - CODE 12: AIRFLOW METER
Fig. 6: Infiniti G20 1991 - Component Locations - Code 12: Airflow Meter Circuit Diagram
Fig. 7: Infiniti G20 1991 - Component Locations - Code 12: Airflow Meter & ECU Harness Location
Fig. 8: Infiniti G20 1991 - Component Locations - Code 12: Airflow Meter Flow Chart (1 of 2)
Fig. 9: Infiniti G20 1991 - Component Locations - Code 12: Airflow Meter Flow Chart (2 of 2)
Infiniti G20 1991 - CODE 13: ENGINE (COOLANT) TEMPERATURE SENSOR
Fig. 10: Infiniti G20 1991 - Component Locations - Code 13: Engine Temp. Sensor Circuit Diagram
Fig. 12: Infiniti G20 1991 - Component Locations - Code 13: Engine Temp. Sensor Flow Chart (1 of 2)
Fig. 13: Infiniti G20 1991 - Component Locations - Code 13: Engine Temp. Sensor Flow Chart (2 of 2)
Infiniti G20 1991 - CODE 14: VEHICLE SPEED SENSOR
Fig. 14: Infiniti G20 1991 - Component Locations - Code 14: Vehicle Speed Sensor Circuit Diagram
Fig. 15: Infiniti G20 1991 - Component Locations - Code 14: Vehicle Speed Sensor Flow Chart
Infiniti G20 1991 - CODE 21: IGNITION SIGNAL CIRCUIT
Fig. 16: Infiniti G20 1991 - Component Locations - Code 21: Ignition Signal Ckt. Circuit Diagram
Fig. 18: Infiniti G20 1991 - Component Locations - Code 21: Ignition Signal Ckt. Flow Chart (1 of 3)
Fig. 19: Infiniti G20 1991 - Component Locations - Code 21: Ignition Signal Ckt. Flow Chart (2 of 3)
Fig. 20: Infiniti G20 1991 - Component Locations - Code 21: Ignition Signal Ckt. Flow Chart (3 of 3)
Infiniti G20 1991 - CODE 31: ENGINE CONTROL UNIT (ECU)
Fig. 21: Infiniti G20 1991 - Component Locations - Code 31: Engine Control Unit (ECU) Flow Chart
Infiniti G20 1991 - CODE 32: EGR SYSTEM FUNCTION
Fig. 22: Infiniti G20 1991 - Component Locations - Code 32: EGR System Function Circuit Diagram
Fig. 24: Infiniti G20 1991 - Component Locations - Code 32: EGR System Function Flow Chart (1 of 4)
Fig. 25: Infiniti G20 1991 - Component Locations - Code 32: EGR System Function Flow Chart (2 of 4)
Fig. 26: Infiniti G20 1991 - Component Locations - Code 32: EGR System Function Flow Chart (3 of 4)
Fig. 27: Infiniti G20 1991 - Component Locations - Code 32: EGR System Function Flow Chart (4 of 4)
Infiniti G20 1991 - CODE 33: OXYGEN SENSOR
Fig. 28: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor Circuit Diagram
Fig. 29: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor & ECU Harness Location
Fig. 30: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor Flow Chart (1 of 4)
Fig. 31: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor Flow Chart (2 of 4)
Fig. 32: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor Flow Chart (3 of 4)
Fig. 33: Infiniti G20 1991 - Component Locations - Code 33: Oxygen Sensor Flow Chart (4 of 4)
Infiniti G20 1991 - CODE 34: KNOCK (DETONATION) SENSOR
Fig. 34: Infiniti G20 1991 - Component Locations - Code 34: Knock Sensor Circuit Diagram
Fig. 35: Infiniti G20 1991 - Component Locations - Code 34: Knock Sensor & ECU Harness Location
Fig. 36: Infiniti G20 1991 - Component Locations - Code 34: Knock Sensor Flow Chart
Infiniti G20 1991 - CODE 35: EXHAUST GAS TEMPERATURE SENSOR
Fig. 37: Infiniti G20 1991 - Component Locations - Code 35: Exhaust Gas Temp. Sensor Circuit Diagram
Fig. 39: Infiniti G20 1991 - Component Locations - Code 35: Exhaust Gas Temp. Sensor Flow Chart
Infiniti G20 1991 - CODE 43: THROTTLE POSITION SENSOR
Fig. 40: Infiniti G20 1991 - Component Locations - Code 43: Throttle Position Sensor Circuit Diagram
Infiniti G20 1991 - CODE 45: INJECTOR LEAK
Fig. 44: Infiniti G20 1991 - Component Locations - Code 45: Injector Leak - Spark Plug Diagram
Fig. 45: Infiniti G20 1991 - Component Locations - Code 45: Injector Leak Flow Chart (1 of 2)
Fig. 46: Infiniti G20 1991 - Component Locations - Code 45: Injector Leak Flow Chart (2 of 2)
Infiniti G20 1991 - SUMMARY
If no hard fault codes (or only pass codes) are present, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.) or intermittent diagnosis procedures.