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Engine Controls - Tests W/o Codes: Diagnosis Infiniti Q45 I

Testing & Diagnostics ~657 words

SYMPTOM DIAGNOSIS

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

  1. Difficult To Start Or No Start
  2. High Idle
  3. Rough Or Unstable Idle
  4. Engine Hesitates Or Misses
  5. Engine Stalls
  6. Engine Lacks Power Or Stumbles
  7. Engine Knocks
  8. Engine Surges
  9. Backfire

TROUBLE SHOOTING PROCEDURES

  1. Ensure fuel pressure is within specification. See BASIC TESTING article in the ENGINE PERFORMANCE Section.
  2. Test fuel injectors. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  3. Inspect throttle body ports and valves for deposits, wear and plugging. Clean or replace as necessary.
  4. Check for spark using spark tester. See BASIC TESTING article in the ENGINE PERFORMANCE Section.
  5. Check idle speed components. Refer to IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  6. Ensure battery is fully charged. Ensure battery maintains at least 9.6 volts during cranking.
  7. Check spark plug for improper gap and fouling.
  8. Ensure no vacuum leaks exist in intake system.
  9. Check fast idle system components. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. On Q45, ensure fast idle cam keeps cam follower lever fully released. If cam follower lever is not kept fully released, check adjustment. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
  10. Check EGR valve operation. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  11. Check EGR solenoid valve operation. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  12. Ensure engine has adequate compression. See BASIC TESTING article in the ENGINE PERFORMANCE Section.
  13. Disconnect exhaust gas sensor, and monitor driveability. If driveability improves, replace sensor. If driveability does not improve, go to step 16).
  14. Remove canister purge line from intake, and test drive vehicle.
  15. Remove vacuum hose from fuel pressure regulator, and monitor for symptom change.
  16. Enter self-diagnostic Mode II, and monitor exhaust gas sensor operation. See FEEDBACK SYSTEM under FUEL CONTROL in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  17. Check ECU harness connector.
  18. Substitute a known good ECU.
  19. Check ECU power supply and ground circuit. See POWER CIRCUITS and GROUND CIRCUITS under ELECTRONIC CONTROL UNIT (ECU) in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  20. Check timing belt for proper installation.
  21. Check throttle linkage operation.
  22. Substitute a known good airflow meter.
  23. Check for intake valve deposits.
  24. Check coolant (engine) temperature sensor. See COOLANT (ENGINE) TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
  25. Check fuel level in tank.
  26. Check for oil leaks into combustion chamber.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify problem. These procedures may lead to the computer setting 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 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

Two different diagnostic modes are available through ECCS. Diagnostic Mode I is used as a bulb check and as a malfunction warning. With ignition on and engine off, Mode II of self-diagnostic system is used for obtaining trouble codes for component or circuit failures. With engine running, Mode II is used for monitoring air/fuel mixture ratio by using Red LED on ECU or CHECK ENGINE light on dash panel.

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

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