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Engine Controls - Tests W/o Codes Lexus ES XV10

Testing & Diagnostics ~1368 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 components for further diagnosis. A symptom should lead to a specific component, system test or 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.

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

DIAGNOSIS BY SYMPTOM

When a diagnostic code cannot be confirmed or problem cannot be confirmed in BASIC TESTING article in the ENGINE PERFORMANCE Section, find basic symptom. For example, vehicle engine will not start. Appropriate heading matching vehicle symptom is DOES NOT START. Listed under DOES NOT START are more specific conditions. Find specific condition which best describes vehicle malfunction. Perform checks in order given. DO NOT skip steps.

Note. Symptom diagnosis may refer to testing using a diagnostic code chart, even if a diagnostic code was not set.

FOLLOWING SYMPTOMS ARE AVAILABLE FOR DIAGNOSIS.

  1. Does Not Start
  2. Difficult To Start
  3. Poor Idling
  4. Poor Driveability
  5. Engine Stall

Engine Does Not Crank

  1. Check starter relay.
  2. Check starter for proper operation.
  3. Check neutral start switch circuit.
  4. Check theft deterrent ECU.

No Initial Combustion

  1. Check ECU power circuit.
  2. Check ignition circuit. See CODE 14 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  3. Check EFI main relay.
  4. Check fuel system circuit.
  5. Check spark plugs.
  6. Check injector circuit.
  7. Check cold start injector system (ES300 only).

No Complete Combustion

  1. Check fuel system circuit.
  2. Ensure ignition coil resistance values are within specification.
  3. Check distributor.
  4. Check spark plugs.
  5. Check ignition circuit. See CODE 14 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  6. Check injector circuit.
  7. Check cold start injector system (ES300 only).

Difficult To Start Normally

  1. Check starter signal circuit. See CODE 43 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check fuel system circuit.
  4. Ensure ignition coil resistance values are within specification.
  5. Check distributor.
  6. Check spark plugs.
  7. Ensure engine compression is within specification.
  8. Check injector circuit.
  9. Check cold start injector system (ES300 only).

Difficult To Start When Cold

  1. Check starter signal circuit. See CODE 43 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check cold start injector system (ES300 only).
  4. Check fuel system circuit.
  5. Check injector circuit.
  6. Ensure ignition coil resistance values are within specification.
  7. Check distributor.
  8. Check spark plugs.

Difficult To Start When Hot

  1. Check starter signal circuit. See CODE 43 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check fuel pressure control VSV circuit (ES300 only).
  4. Check fuel system circuit.
  5. Check injector circuit.
  6. Check cold start injector system (ES300 only).
  7. Ensure ignition coil resistance values are within specification.
  8. Check distributor.
  9. Check spark plugs.

Incorrect First Idle

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.

High Idle Speed

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check A/C signal circuit. Ensure A/C clutch is engaged.
  4. Check ECU power circuit.
  5. Check neutral start switch circuit.
  6. Check ECU memory power circuit.

Low Idle Speed

  1. Check idle speed control valve circuit.
  2. Check A/C signal circuit. Ensure A/C clutch is engaged.
  3. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  4. Check neutral start switch circuit.
  5. Check fuel system circuit.
  6. Check injector circuit.
  7. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (CODE 32 on ES300 only).
  8. Check ECU memory power circuit.

Rough Idle

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (Code 32 on ES300 only).
  4. Check injector circuit.
  5. Check EGR system.
  6. Check ignition circuit. See CODE 14 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  7. Ensure engine compression is within specification.
  8. Check fuel system circuit.
  9. Ensure ignition coil resistance values are within specification.
  10. Check distributor.
  11. Check spark plugs.
  12. Check ECU memory power circuit.
  13. Check cold start injector system (ES300 only).

Hunting

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (CODE 32 on ES300 only).
  4. Check ECU power circuit.
  5. Check fuel system circuit.

Hesitation, Poor Acceleration

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (CODE 32 on ES300 only).
  3. Check injector circuit.
  4. Check fuel system circuit.
  5. Check ignition circuit. See CODE 14 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  6. Ensure ignition coil resistance values are within specification.
  7. Check distributor.
  8. Check spark plugs.
  9. Check A/C cut-out circuit (ES300 only)
  10. Check for faulty ECT.

Muffler Explosion (After Fire)

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Ensure ignition coil resistance values are within specification.
  3. Check distributor.
  4. Check spark plugs.
  5. Check injector circuit.

Surging

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check fuel system circuit.
  3. Check distributor.
  4. Check spark plugs.
  5. Check injector circuit.

Engine Stall After Start

  1. Check fuel system circuit.
  2. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (CODE 32 on ES300 only).
  3. Check idle speed control valve circuit.
  4. Check cold start injector system (ES300 only).

Engine Stall After Acceleration Pedal Depressed

  1. Check switch condition signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check airflow meter circuit. See CODE 31 and CODE 32 in TESTS W/CODES article in the ENGINE PERFORMANCE Section. (CODE 32 on ES300 only).
  3. Check cold start injector system (ES300 only).

Engine Stall After Acceleration Pedal Released

  1. Check injector circuit.
  2. Check idle speed control valve circuit.
  3. Check cold start injector system (ES300 only).
  4. Check ECU ground circuit.

Engine Stall During A/C Operation

  1. Check idle speed control valve circuit.
  2. Check A/C signal circuit. Ensure A/C clutch is engaged.
  3. Check ECU ground circuit.

Engine Stall When Shifting From Neutral To Drive

  1. Check neutral start switch signal. See CODE 51 in TESTS W/CODES article in the ENGINE PERFORMANCE Section.
  2. Check idle speed control valve circuit.
  3. Check cold start injector system (ES300 only).

INTERMITTENT PROBLEM DIAGNOSIS

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

To reproduce conditions creating an intermittent fault

  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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