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Engine Controls - Trouble Shooting - No Codes Suzuki Grand Vitara I

Testing & Diagnostics ~1236 words

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in BASIC DIAGNOSTIC PROCEDURES and appropriate SELF-DIAGNOSTICS articles. Use this article to diagnose driveability problems existing when a hard trouble 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, system test or an adjustment.

Use INTERMITTENT SIMULATION under 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.

Most intermittent faults are caused by faulty electrical connections or wiring. Perform careful inspection of suspect circuits for

  1. Poor mating of coupler halves, or terminals not fully seated in coupler body (backed out).
  2. Terminals damaged or improperly formed. Reform coupler terminals in problem circuit to increase contact tension.
  3. Poor terminal-to-wire connection.

Note. For specific testing procedures, see SYSTEM & COMPONENT TESTING article. For specifications, see ON-VEHICLE ADJUSTMENTS or SERVICE & ADJUSTMENT SPECIFICATIONS article.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC DIAGNOSTIC PROCEDURES and appropriate SELF-DIAGNOSTICS articles were performed before diagnosing a symptom. Symptoms available for diagnosis include

  1. Difficult Or No Start (Cranks Okay)
  2. Engine Misfires Or Has Lack Of Power
  3. Rough Or Unstable Idle
  4. Engine Hesitates
  5. Engine Surges
  6. Spark Knock/Detonation
  7. Poor Fuel Mileage
  8. Fails Emission Test
  9. Overheating

DIFFICULT OR NO START (CRANKS OKAY)

  1. Check for dirty or clogged fuel filter.
  2. Check for lack of fuel in tank.
  3. Check fuel pressure and volume.
  4. Check for contaminated fuel.
  5. Check for vacuum leaks.
  6. Check for low compression.
  7. Check for blown ignition fuse.
  8. Check ignition and valve timing.
  9. Check spark plugs.
  10. Check for adequate spark with a spark tester.
  11. Check for faulty ignitor/coil assembly.
  12. Check for faulty Engine Coolant Temperature (ECT) sensor.
  13. Check for faulty Mass Airflow (MAF) sensor.
  14. Check for faulty Idle Air Control (IAC) valve.
  15. Check for faulty power unit.
  16. Check for faulty Camshaft Position (CMP) or Crankshaft Position (CKP) sensor.
  17. Check for malfunctioning PCM.
  18. Check for malfunctioning electronic fuel injection system.
  19. Check for slipped or broken timing belt.

ENGINE MISFIRES OR HAS LACK OF POWER

  1. Check ignition and valve timing.
  2. Check spark plugs.
  3. Check for high resistance in spark plug wires (if equipped).
  4. Check for adequate spark with a spark tester.
  5. Check fuel pressure.
  6. Check cooling system.
  7. Check for dirty or clogged fuel filter.
  8. Check for contaminated fuel.
  9. Check for clogged air filter.
  10. Check for low compression.
  11. Check for vacuum leaks.
  12. Check for restricted exhaust system.
  13. Check for malfunctioning electronic fuel injection system.
  14. Check for malfunctioning EGR valve.
  15. Check for dragging brakes.
  16. Check for slipping clutch.
  17. Check for low automatic transmission fluid level.

ROUGH OR UNSTABLE IDLE

  1. Check for contaminated fuel.
  2. Check fuel pressure.
  3. Check EVAP control system.
  4. Check for clogged air filter.
  5. Check for vacuum leaks.
  6. Check cooling system condition.
  7. Check compression.
  8. Check spark plugs.
  9. Check for leaking or loose spark plug wires.
  10. Check for adequate spark with a spark tester.
  11. Check idle speed.
  12. Check ignition and valve timing.
  13. Clogged MAP sensor vacuum hose.
  14. Check for faulty PCM.
  15. Check Power Steering Pressure (PSP) switch circuit.
  16. Check for faulty Engine Coolant Temperature (ECT) sensor.
  17. Check for faulty A/C vacuum switching valve (if equipped).
  18. Check for faulty Idle Air Control (IAC) solenoid valve.
  19. Check for malfunctioning EGR valve.
  20. Check for malfunctioning PCV valve.
  21. Check for malfunctioning electronic fuel injection system.

ENGINE HESITATES

  1. Check fuel pressure.
  2. Check EVAP control system.
  3. Check for clogged fuel filter.
  4. Check for contaminated fuel.
  5. Check for clogged air filter.
  6. Check for restricted exhaust system.
  7. Check ignition and valve timing.
  8. Check spark plugs.
  9. Check for adequate spark with a spark tester.
  10. Check for high resistance in spark plug wires (if equipped).
  11. Check cooling system condition.
  12. Check for low compression.
  13. Check for vacuum leaks.
  14. Check Throttle Position (TP) sensor.
  15. Check for clogged MAP sensor vacuum hose.
  16. Check for faulty PCM.
  17. Check for faulty Engine Coolant Temperature (ECT) sensor.
  18. Check for malfunctioning electronic fuel injection system.
  19. Check for malfunctioning EGR valve.

ENGINE SURGES

  1. Check spark plugs.
  2. Check for adequate spark with a spark tester.
  3. Check for high resistance in spark plug wires.
  4. Check fuel pressure.
  5. Check EVAP control system.
  6. Check for clogged fuel filter.
  7. Check for damaged or kinked fuel lines.
  8. Check for vacuum leaks.
  9. Check ignition and valve timing.
  10. Check for faulty PCM.
  11. Check for malfunctioning electronic fuel injection system.
  12. Check for malfunctioning EGR valve.

SPARK KNOCK/DETONATION

  1. Check cooling system.
  2. Check fuel pressure.
  3. Check spark plugs.
  4. Check for adequate spark with a spark tester.
  5. Check ignition and valve timing.
  6. Check for clogged fuel filter.
  7. Check for vacuum leaks.
  8. Check for excessive combustion chamber deposits.
  9. Check for engine overheating.
  10. Check for malfunctioning electronic fuel injection system.
  11. Check for malfunctioning EGR valve.

POOR FUEL MILEAGE

  1. Check for fuel leaks.
  2. Check fuel pressure regulator.
  3. Check for clogged air filter.
  4. Check compression.
  5. Check cooling system condition.
  6. Check ignition and valve timing.
  7. Check spark plugs.
  8. Check for faulty Engine Coolant Temperature (ECT) sensor.
  9. Check for faulty thermostat.
  10. Check for faulty PCM.
  11. Check for high idle RPM.
  12. Check for malfunctioning electronic fuel injection system.
  13. Check for brakes dragging.
  14. Check for clutch slipping.
  15. Check for low automatic transmission fluid.
  16. Check for improper tire pressure.

FAILS EMISSION TEST

  1. Check for clogged air filter.
  2. Check for abnormal engine operating temperature.
  3. Check for fuel leakage from injectors.
  4. Check for fuel pressure out of specification.
  5. Check for faulty Engine Coolant Temperature (ECT) sensor.
  6. Check for faulty PCM.
  7. Check for faulty EGR system.
  8. Check for improper ignition timing.
  9. Check for malfunctioning ignition system.
  10. Check for lead contamination in catalytic converter.
  11. Check for misrouted vacuum hoses.
  12. Check for poor compression.
  13. Check for vacuum leaks.

OVERHEATING

  1. Check for insufficient coolant.
  2. Check for loose water pump belt.
  3. Check for faulty thermostat.
  4. Check for poor water pump performance.
  5. Check for improper ignition timing.
  6. Check for clogged or leaky radiator.
  7. Check for low oil level.
  8. Check for poor oil pump performance.
  9. Check for dragging brakes.
  10. Check for blown cylinder head gasket.

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 trouble code which may help in diagnosis.

If problem vehicle does not produce trouble 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 switch is in ON position or engine is running. Ensure ignition switch 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.

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 mist.
  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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