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Engine Controls - Tests W/o Codes Nissan Stanza III

Testing & Diagnostics ~2420 words

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES articles in the ENGINE PERFORMANCE Section. Use this article to diagnose driveability problems existing when a hard fault code is not present.

Note. Some driveability problems may have been corrected by manufacturer with a revised computer calibration chip or computer control unit. Check with manufacturer for latest chip or computer application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component test, system test or an adjustment.

Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

The recommended procedures for each symptom will be indicated by number(s) from 1-to-25, and may also contain specific instructions related to that number. For a definition of each procedure, refer to appropriate SYMPTOM PROCEDURE DEFINITION in this article. Not all recommended procedures apply to all vehicles.

Note. For specific testing procedures, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. For specifications, see ADJUSTMENTS or SPECIFICATIONS article in the ENGINE PERFORMANCE Section.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and TESTS W/CODES article in the ENGINE PERFORMANCE Section were performed before diagnosing a symptom. Symptoms available for diagnosis include the following

  1. Hard Start/Will Not Start - Cold, Normal Conditions, Hot
  2. High Idle - Warm
  3. Unstable Idling - After Warm-Up, Hunting
  4. Hesitation - Cold, Normal Conditions, Hot
  5. Poor Driveability - Lack Of Power/Stumble, Surge, Detonation
  6. Engine Stall - Cold, Hot, On Momentary Acceleration, After Deceleration, Acceleration Or Cruising, Heavy Electrical Load, While Turning
  7. Backfire - Intake, Exhaust.

Note. Recommended procedures for symptoms listed above are given in numbers from 1-to-25. See SYMPTOM PROCEDURE DEFINITION for interpretations.

Cold

  1. Ensure battery is fully charged and maintains at least 9.6 volts during cranking.
  2. Ensure fuel pressure is within specification.
  3. Check fast idle system. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS .
  4. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  5. Check for spark using spark tester.
  6. Check spark plug for improper gap or fouling.
  7. Check ECU harness connector.
  8. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  9. Try a known good ECU.

Normal Conditions

  1. Ensure battery is fully charged and maintains at least 9.6 volts during cranking.
  2. Ensure fuel pressure is within specification.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Check spark plug for improper gap or fouling.
  6. Check EGR control valve operation.
  7. Check ECU harness connector.
  8. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  9. Try a known good ECU.
  10. Check timing belt for proper installation (V6 models).

Hot

  1. Ensure fuel pressure is within specification.
  2. Remove vacuum hose from fuel pressure regulator and monitor for symptom change.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Check ECU harness connector.
  6. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  7. Try a known good ECU.

Warm

  1. Check idle speed control circuit. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article.
  2. Ensure there are no vacuum leaks into intake system.
  3. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 16.
  4. Check throttle linkage operation.

After Warm-Up

  1. Check EGR control valve operation.
  2. Perform power balance test.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Check spark plug for improper gap or fouling.
  6. Ensure fuel pressure is within specification.
  7. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 16.
  8. Ensure there are no vacuum leaks into intake system.
  9. Inspect throttle body ports and valves for deposits, wear or plugging. Clean or replace as necessary.
  10. Ensure engine has adequate compression.
  11. Check ECU harness connector.
  12. Try a known good ECU.

Hunting

  1. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 16.
  2. Perform power balance test.
  3. Check spark plug for improper gap or fouling.
  4. Ensure there are no vacuum leaks into intake system.
  5. Check EGR control valve operation.
  1. Check spark plug for improper gap or fouling.
  2. Ensure there are no vacuum leaks into intake system.
  3. Try a known good airflow meter.
  4. Check for intake valve deposits.

Under Normal Conditions

  1. Check spark plug for improper gap or fouling.
  2. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 16.
  3. Remove canister purge line from intake and test drive vehicle.
  4. Ensure there are no vacuum leaks into intake system.
  1. Remove vacuum hose from fuel pressure regulator and monitor for symptom change.
  2. Remove canister purge line from intake and test drive vehicle.
  3. For NX & Sentra Ensure there are no vacuum leaks into intake system.

Lack Of Power/Stumble

  1. Ensure fuel pressure is within specification.
  2. Ensure there are no vacuum leaks into intake system.
  3. Check timing belt for proper installation (V6 models).

Surge

  1. Enter self-diagnostic Mode II and monitor exhaust gas sensor operation (fuel metering system operation on Maxima, Pathfinder and Pickup V6).
  2. Check EGR control valve operation.
  3. Try a known good ECU.

Detonation

  1. Ensure there are no vacuum leaks into intake system.
  2. Check EGR control valve operation.
  3. Check EGR control valve solenoid operation.
  4. Check spark plug for improper gap or fouling.
  1. Check fast idle system. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS .
  2. Perform power balance test.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Check spark plug for improper gap or fouling.
  6. Ensure fuel pressure is within specification.
  7. Check ECU harness connector.
  8. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  9. Try a known good ECU.
  1. Remove vacuum hose from fuel pressure regulator and monitor for symptom change.
  2. Perform power balance test.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Ensure fuel pressure is within specification.
  6. Check ECU harness connector.
  7. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  8. Try a known good ECU.
  9. Check timing belt for proper installation (V6 models).

On Momentary Acceleration

  1. Check fast idle system. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS .
  2. Perform power balance test.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Check spark plug for improper gap or fouling.
  6. Ensure fuel pressure is within specification.
  7. Check ECU harness connector.
  8. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  9. Try a known good ECU.

After Deceleration

  1. Check fast idle system. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS .
  2. Inspect throttle body ports and valves for deposits, wear or plugging. Clean or replace as necessary.
  3. Perform power balance test.
  4. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  5. Check for spark using spark tester.
  6. Ensure fuel pressure is within specification.
  7. Disconnect exhaust gas sensor and monitor change in driveability. If it improves, replace sensor. If not, go to 16.
  8. Check ECU harness connector.
  9. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  10. Try a known good ECU.

Acceleration Or Cruising

  1. Perform power balance test.
  2. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  3. Check for spark using spark tester.
  4. Ensure fuel pressure is within specification.
  5. Ensure there are no vacuum leaks into intake system.
  6. Check ECU harness connector.
  7. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  8. Try a known good ECU.

Heavy Electrical Load

  1. Ensure battery is fully charged and maintains at least 9.6 volts during cranking.
  2. Perform power balance test.
  3. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  4. Check for spark using spark tester.
  5. Ensure fuel pressure is within specification.
  6. Check ECU harness connector.
  7. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  8. Try a known good ECU.

While Turning - Check fuel level

  1. Perform power balance test.
  2. Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
  3. Check for spark using spark tester.
  4. Ensure fuel pressure is within specification.
  5. Check ECU harness connector.
  6. Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS. Use DIAGNOSTIC CHARTS DIRECTORY TABLE in I - SYS/COMP TESTS article to locate chart.
  7. Try a known good ECU.

Intake

  1. Check spark plug for improper gap or fouling.
  2. Ensure there are no vacuum leaks into intake system.
  3. Check for intake valve deposits.
  4. Check engine temperature sensor. See ENGINE (COOLANT) TEMPERATURE SENSOR in I - SYS/COMP TESTS article.

Exhaust

  1. Check engine temperature sensor. See ENGINE (COOLANT) TEMPERATURE SENSOR in I - SYS/COMP TESTS article.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code (on some systems) which may help in diagnosis.

If problem vehicle does not produce fault codes, monitor voltage or resistance values using a DVOM while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates a fault has been located.

Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition is in ON position, or engine is running. Ensure ignition is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.

TEST PROCEDURES (NX, SENTRA, STANZA, 240SX & 300ZX)

Two different diagnostic modes are available through the ECCS. Diagnostic Mode I is used as a bulb check and malfunction warning. Mode II is the self-diagnostic system and is used to obtain trouble codes for component or circuit failures. Mode II also monitors air/fuel mixture ratio by using the Red LED on ECU and CHECK ENGINE light.

Note. For additional information on self-diagnostic system, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods.

  1. Lightly vibrate component.
  2. Heat component.
  3. Wiggle or bend wiring harness.
  4. Spray component with water.
  5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.

TEST PROCEDURES (MAXIMA, PATHFINDER & PICKUP)

Five different diagnostic modes are available through the ECCS. Diagnostic Mode I and Mode II monitor air/fuel mixture ratio using LED inspection lights. Mode III is the self-diagnostic system and is used to obtain trouble codes for component or circuit failures. Mode IV monitors for malfunction(s) in the system's on-off control switches. Mode V is the real-time diagnostic system; it monitors the system and its components during actual driving, usually to simulate intermittent condition.

Note. For additional information on self-diagnostic system, see TESTS W/CODES article.

Mode V

Mode V detects problems when system is active. The moment a malfunction is detected, the Red and Green LEDs on side of ECU will display malfunction code.

  1. While operating vehicle in self-diagnostic Mode V, observe inspection lights. Operate vehicle under conditions which malfunction or intermittent seems to occur.
  2. If malfunction code is indicated, repair related circuit for intermittent problem. If no intermittent fault is indicated, go to INTERMITTENT SIMULATION.

To reproduce the conditions creating an intermittent fault, use the following methods.

  1. Lightly vibrate component.
  2. Heat component.
  3. Wiggle or bend wiring harness.
  4. Spray component with water.
  5. Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.

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