Engine Controls - Tests W/codes Nissan Maxima J30

INTRODUCTION

If no faults were found while performing BASIC TESTING proceed with self-diagnostics. If no fault codes or only pass codes are present after entering self-diagnostics, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

SELF-DIAGNOSTIC SYSTEM

Self-diagnostic system is used for diagnosing malfunctions of Electronic Concentrated Control System (ECCS) sensors and actuators. Electronic Control Unit (ECU) has a number of available diagnostic modes within computer.

Maxima has 5 diagnostic modes. All others have 2 modes with subdivisions. Before selecting any mode of self-diagnosis, always perform procedures listed in BASIC TESTING article in the ENGINE PERFORMANCE Section. Doing so prevents wasted time and invalid diagnostic results.

Note. When performing BASIC TESTING be careful not to erase any diagnostic information stored in ECU memory.

HARD FAILURES

Hard failures cause CHECK ENGINE light (if equipped) 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, ECU will use a substitute value in its calculations to continue engine operation. In this condition (fail-safe mode), the vehicle runs but driveability will not be optimum and engine speed is restricted (2000-3000 RPM depending on model).

INTERMITTENT FAILURES

Intermittent failures may cause CHECK ENGINE light (if equipped) to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in ECU memory. If related fault does not reoccur within 50 ignition switch operations, related trouble code will be erased from ECU memory. Intermittent failures may be caused by sensor, connector or wiring problems. See INTERMITTENTS in TESTS W/O CODES article.

Note. Follow diagnostic routine when testing ECCS. See DIAGNOSTIC ROUTINE table for correct order of procedure.

DIAGNOSTIC ROUTINE

CHECK ENGINE LIGHT

Maxima is equipped with a CHECK ENGINE light. As a bulb check, light will illuminate when ignition is on and engine is not running. CHECK ENGINE light will also illuminate when an ECCS fault has been detected. Not all trouble codes activate CHECK ENGINE light.

DIAGNOSTIC MODES

Self-diagnostic system can detect ECCS malfunctions and store related trouble codes. Trouble codes, including intermittent codes, are stored in ECU memory and are available for interpretation unless codes have been cleared.

Self-diagnostic system uses dual Light Emitting Diodes (LEDs), located on ECU.

Mode I (Exhaust Gas Monitor)

This is normal vehicle operating mode. Green LED will indicate loop status. If green LED is not blinking, vehicle is in open loop or a fault exists with oxygen sensor or sensor circuit. If green LED is blinking, vehicle is in closed loop. If a malfunction occurs in Mode I, red LED and CHECK ENGINE light (if equipped) will illuminate, indicating an ECCS malfunction has occurred.

Mode II (Mixture Ratio Feedback Monitor)

In Mode II, both red and green LEDs are used to monitor air/fuel mixture feedback control. Green LED will function as in Mode I. In open loop, red LED and green LED will remain on or off. For results to be valid, vehicle must be in closed loop. In closed loop, red LED will indicate if system is running rich (light off), lean (light on) or at ideal air/fuel ratio (blinking synchronized with green LED).

Mode III (Self-Diagnostics)

When Mode III is accessed, codes stored in ECU memory will be flashed by green and red LEDs on side of ECU. Green light will flash tens column digit, while red LED will flash ones column digit. For example: 3 flashes of green LED followed by 5 flashes of red LED indicate a Code 35.

Mode IV (Switch Check)

This mode is used for checking ECCS switch status. When idle switch or starter switch is activated, red LED will come on and go off as status changes. For vehicle speed sensor status, green LED will remain off when vehicle speed is less than 12 MPH and come on when vehicle speed is greater than 12 MPH.

Mode V (Test Mode)

Mode V represents a real-time diagnostic test of crank angle sensor, ignition signal, airflow output signal and fuel pump (Maxima). This mode is accessed for an in-bay running test of vehicle. Red and green LEDs must be monitored carefully during this test, with special attention paid to number of flashes before each pause.

Malfunction code will be displayed only once and will not be stored in memory. If red LED blinks on and off evenly, a fault exists in crank angle sensor. If green LED flashes twice before a pause, a fault exists in airflow meter. If red LED blinks 3 times before a pause, a fault exists in fuel pump circuit. If green LED blinks 4 times before a pause, a fault exists in ignition signal.

ENTERING SELF-DIAGNOSTICS

1. Turn ignition switch to ON position. Use a screwdriver to turn ECU diagnostic mode selector fully clockwise.
2. Wait for inspection lights to begin flashing. At this time, inspection lights will flash mode options (i.e., one flash for Mode I, 2 flashes for Mode II, etc.). As soon as inspection light flashes desired mode number (3 flashes for self-diagnostic mode), turn mode selector off (fully counterclockwise).
3. If mode selector is kept in ON position (fully clockwise), mode selections will continuously cycle. This cycling will not erase memory.

RETRIEVING CODES

Trouble codes are read using red and green LED inspection lights on side of ECU. After selecting Mode III, trouble codes corresponding to mode will start flashing. Trouble codes are indicated by number of flashes from ECU red and green LED inspection lights. Count number of flashes. Red LED indicates number of tens while green LED indicates number of ones. For example, 3 flashes of red LED followed by 2 flashes of green LED indicate Code 32.

TROUBLE CODE DEFINITION

TROUBLE CODE IDENTIFICATION CHART

CLEARING CODES

Note. Ensure all diagnostic codes are extracted from ECU memory before disconnecting battery or manually erasing stored memory.

Memory Erase

Stored memory will be erased if battery is disconnected for 24 hours or Mode IV is selected after Mode III has been accessed. However, if mode selector switch is turned fully clockwise, diagnostic modes will continue to cycle until a mode is selected. This cycling does not erase stored memory.

ECU LOCATION

ECU LOCATION

Note. When CODE CHART step indicates CHECK COMPONENT, see indicated component in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

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Final Steps For All Code Charts

Unless otherwise instructed in code chart, perform following steps after repair

1. Reinstall any part removed.
2. Erase self-diagnostic memory. See CLEARING CODES under SELF-DIAGNOSTIC SYSTEM.
3. Ensure Code 55 (no malfunction) is displayed in self-diagnostic mode.
4. Test drive vehicle.
5. Perform self-diagnosis.

If code resets, check for damage to ECU pin terminals and connector harness.

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SUMMARY

If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

See also:
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