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Engine Controls - Tests W/o Codes Lexus LS I

Testing & Diagnostics ~4287 words

INTRODUCTION

Note. F - BASIC TESTING, TESTS W/CODES , SYSTEM/COMP TESTS , ADJUSTMENTS , and SPECIFICATIONS articles are all in the ENGINE PERFORMANCE Section.

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES article s. Use this article to diagnose driveability problems existing when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system.

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 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 SYSTEM/COMP TESTS article. For specifications, see ADJUSTMENTS or SPECIFICATIONS articles.

LS400 DIAGNOSIS BY SYMPTOM

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

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

ENGINE DOES NOT START

  1. Check starter relay. See SYSTEM/COMP TESTS article.
  2. Check starter for proper operation.
  3. Check ECU. See ECU POWER SOURCE CIRCUIT chart in TESTS W/CODES article.
  4. Check neutral start switch. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
  5. Check theft deterrent ECU. See SYSTEM/COMP TESTS article.

STARTER RUNS, ENGINE DOES NOT CRANK

  1. Check starter for proper operation.
  2. Check for engine mechanical failure.
  3. Check flywheel or flexplate for damage.

NO INITIAL COMBUSTION

  1. Check ECU. See ECU POWER SOURCE CIRCUIT chart in TESTS W/CODES article.
  2. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  3. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  4. Check ignition coil. See SYSTEM/COMP TESTS article.
  5. Check spark plugs.
  6. Check injectors. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  7. Check engine compression.
  8. Check cold start injector. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  9. Check RPM signal circuit. See CODE 12, CODE 17 and CODE 18 in TESTS W/CODES article.
  10. Check engine for mechanical failure.
  11. Check ECU. See SYSTEM/COMP TESTS article.

NO COMPLETE COMBUSTION

  1. Check for vacuum leaks.
  2. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  3. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  4. Check ignition coil. See SYSTEM/COMP TESTS article.
  5. Check distributor and spark plugs.
  6. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  7. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  8. Check engine compression.
  9. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  10. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  11. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  12. Check engine for mechanical failure.
  13. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE CRANKS SLOWLY

  1. Check starter for proper operation.
  2. Check fuel quality.
  3. Check engine for mechanical failure.

DIFFICULT TO START NORMALLY

  1. Check for vacuum leaks.
  2. Check fuel quality.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  5. Check EGR system. See CODE 71 in TESTS W/CODES article.
  6. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  7. Check ignition coil. See SYSTEM/COMP TESTS article.
  8. Check distributor and spark plugs.
  9. Check engine compression.
  10. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  11. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  12. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  13. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  14. Check engine for mechanical failure.
  15. Check ECU. See SYSTEM/COMP TESTS article.

DIFFICULT TO START COLD

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check starter signal circuit. See CODE 43 in TESTS W/CODES article.
  3. Check for vacuum leaks.
  4. Check fuel quality.
  5. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  6. Check EGR system. See CODE 71 in TESTS W/CODES article.
  7. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  8. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  9. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  10. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  11. Check ignition coil. See SYSTEM/COMP TESTS article.
  12. Check distributor and spark plugs.
  13. Check ECU. See SYSTEM/COMP TESTS article.

DIFFICULT TO START HOT

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check for vacuum leaks.
  3. Check fuel quality.
  4. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  5. Check fuel pressure control vacuum switching valve circuit. See FUEL PRESSURE CONTROL VACUUM SWITCHING VALVE (VSV) CIRCUIT chart in TESTS W/CODES article.
  6. Check EGR system. See CODE 71 in TESTS W/CODES article.
  7. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  8. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  9. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  10. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  11. Check ignition coil. See SYSTEM/COMP TESTS article.
  12. Check distributor and spark plugs.
  13. Check ECU. See SYSTEM/COMP TESTS article.

INCORRECT FIRST IDLE

  1. Check accelerator pedal linkage.
  2. Check dashpot. See SYSTEM/COMP TESTS article.
  3. Check power steering system for proper operation.
  4. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  5. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  6. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  7. Check ECU. See SYSTEM/COMP TESTS article.

HIGH IDLE SPEED

  1. Check accelerator pedal linkage.
  2. Check dashpot. See SYSTEM/COMP TESTS article.
  3. Check power steering system for proper operation.
  4. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  5. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  6. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  7. Check A/C signal circuit. See A/C SIGNAL CIRCUIT chart in TESTS W/CODES article.
  8. Check ECU power source. See ECU POWER SOURCE CIRCUIT chart in TESTS W/CODES article.
  9. Check neutral start switch circuit. See CODE 51 in TESTS W/CODES article.
  10. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  11. Check ECU. See SYSTEM/COMP TESTS article.

LOW IDLE SPEED

  1. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  2. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  3. Check neutral start switch circuit. See CODE 51 in TESTS W/CODES article.
  4. Check EGR system. See CODE 71 in TESTS W/CODES article.
  5. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  6. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  7. Check ECU. See SYSTEM/COMP TESTS article.

ROUGH IDLE

  1. Check for vacuum leaks.
  2. Check fuel quality.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check EGR system. See CODE 71 in TESTS W/CODES article.
  5. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  6. Check engine compression.
  7. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  8. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  9. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  10. Check ignition coil. See SYSTEM/COMP TESTS article.
  11. Check distributor and spark plugs.
  12. Check back-up power source circuit. See BACK-UP POWER SOURCE CIRCUIT chart in TESTS W/CODES article.
  13. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  14. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  15. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  16. Check engine for mechanical failure.
  17. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE MISFIRE

  1. Check for vacuum leaks.
  2. Check fuel quality.
  3. Check EGR system. See CODE 71 in TESTS W/CODES article.
  4. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  5. Check distributor and spark plugs.
  6. Check ignition coil. See SYSTEM/COMP TESTS article.
  7. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  8. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  9. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  10. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  11. Check engine compression.
  12. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  13. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  14. Check engine for mechanical failure.
  15. Check ECU. See SYSTEM/COMP TESTS article.

HESITATION, POOR ACCELERATION

  1. Check for vacuum leaks.
  2. Check accelerator pedal linkage.
  3. Ensure brakes do not drag.
  4. Check fuel quality.
  5. Check EGR system. See CODE 71 in TESTS W/CODES article.
  6. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  7. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  8. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  9. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  10. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  11. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  12. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  13. Check ignition coil. See SYSTEM/COMP TESTS article.
  14. Check distributor and spark plugs.
  15. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  16. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  17. Ensure transmission is functioning properly.
  18. Check sub-throttle valve for proper operation.
  19. Check engine for mechanical failure.
  20. Check ECU. See SYSTEM/COMP TESTS article.

BACKFIRE

  1. Check for vacuum leaks.
  2. Check EGR system. See CODE 71 in TESTS W/CODES article.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  5. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  6. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  7. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  8. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  9. Check engine for mechanical failure.
  10. Check ECU. See SYSTEM/COMP TESTS article.

MUFFLER EXPLOSION (AFTER FIRE)

  1. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  2. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  3. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  4. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  5. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  6. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  7. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  8. Check ignition coil. See SYSTEM/COMP TESTS article.
  9. Check distributor and spark plugs.
  10. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  11. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  12. Check engine for mechanical failure.
  13. Check ECU. See SYSTEM/COMP TESTS article.

SURGING

  1. Check for vacuum leaks.
  2. Check fuel quality.
  3. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  4. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  5. Check EGR system. See CODE 71 in TESTS W/CODES article.
  6. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  7. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  8. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  9. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  10. Check distributor and spark plugs.
  11. Check engine compression.
  12. Check ignition signal circuit. See SPARK TEST in BASIC TESTING article.
  13. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  14. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  15. Check engine for mechanical failure.
  16. Check ECU. See SYSTEM/COMP TESTS article.

KNOCKING

  1. Check fuel quality.
  2. Check knock sensor circuit. See CODE 52, CODE 53 and CODE 55 in TESTS W/CODES article.
  3. Check spark plugs.
  4. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  5. Check EGR system. See CODE 71 in TESTS W/CODES article.
  6. Check engine for mechanical failure.
  7. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALLS AFTER STARTING

  1. Check for vacuum leaks.
  2. Check fuel quality.
  3. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  4. Check EGR system. See CODE 71 in TESTS W/CODES article.
  5. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  6. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  7. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  8. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  9. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  10. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL AFTER ACCELERATION PEDAL DEPRESSED

  1. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  2. Check EGR system. See CODE 71 in TESTS W/CODES article.
  3. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  4. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL AFTER ACCELERATION PEDAL RELEASED

  1. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  2. Check EGR system. See CODE 71 in TESTS W/CODES article.
  3. Check airflow meter circuit. See CODE 31 in TESTS W/CODES article.
  4. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL DURING A/C OPERATION

  1. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  2. Check A/C signal circuit. See A/C COMPRESSOR CIRCUIT chart.
  3. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL WHEN SHIFTING FROM NEUTRAL TO DRIVE

  1. Check neutral start switch circuit. See CODE 51 in TESTS W/CODES article.
  2. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  3. Check ECU. See SYSTEM/COMP TESTS article.

ENGINE STALL WHEN TURNING STEERING

  1. Check power steering system for proper operation.

ENGINE STALL WHEN STARTING OFF OR STOPPING

  1. Ensure transmission is functioning properly.

POOR FUEL ECONOMY

  1. Check for fuel leaks.
  2. Check fuel quality.
  3. Ensure brakes do not drag.
  4. Check accelerator pedal linkage.
  5. Ensure cooling system is functioning properly.
  6. Check water temperature sensor circuit. See CODE 22 in TESTS W/CODES article.
  7. Check intake air temperature sensor circuit. See CODE 24 in TESTS W/CODES article.
  8. Check throttle position sensor circuit. See CODE 41 and CODE 47 in TESTS W/CODES article.
  9. Check spark plugs.
  10. Check ignition coil. See SYSTEM/COMP TESTS article.
  11. Check distributor.
  12. Check engine compression.
  13. Check fuel system circuit. See FUEL SYSTEM CIRCUIT chart in TESTS W/CODES article.
  14. Check injector circuit. See INJECTOR CIRCUIT chart in TESTS W/CODES article.
  15. Check fuel pressure control vacuum switching valve circuit. See FUEL PRESSURE CONTROL VACUUM SWITCHING VALVE (VSV) CIRCUIT chart in TESTS W/CODES article.
  16. Check cold start injector circuit. See COLD START INJECTOR CIRCUIT chart in TESTS W/CODES article.
  17. Check idle speed control valve circuit. See IDLE SPEED CONTROL (ISC) VALVE CIRCUIT chart in TESTS W/CODES article.
  18. Check neutral start switch circuit. See CODE 51 in TESTS W/CODES article.
  19. Check main oxygen sensor circuit. See CODE 25 and CODE 26 in TESTS W/CODES article.
  20. Check sub-oxygen sensor circuit. See CODE 27 and CODE 29 in TESTS W/CODES article.
  21. Ensure transmission is functioning properly.
  22. Check engine for mechanical failure.
  23. Check ECU. See SYSTEM/COMP TESTS article.

LS400 DIAGNOSIS BY SYMPTOM (TRANSMISSION)

As an example, vehicle transmission exhibits a harsh engagement. The appropriate heading matching vehicle symptom is HARSH ENGAGEMENT. Listed under HARSH ENGAGEMENT are more specific conditions. Find the condition which best describes your vehicle malfunction. Perform checks in order given. DO NOT skip sequence.

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

VEHICLE DOES NOT MOVE IN ANY GEAR SELECTION

  1. Check transmission for mechanical failure.

VEHICLE DOES NOT MOVE IN A PARTICULAR GEAR SELECTION

  1. Check transmission for mechanical failure.

NO UPSHIFT 1ST To 2ND

  1. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  2. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  3. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  4. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  5. Check transmission for mechanical failure.
  6. Check ECU. See SYSTEM/COMP TESTS article.

NO UPSHIFT 2ND TO 3RD

  1. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  2. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  3. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  4. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  5. Check transmission for mechanical failure.
  6. Check ECU. See SYSTEM/COMP TESTS article.

NO UPSHIFT 3RD To O/D

  1. Check O/D switch and O/D OFF indicator light circuit. See O/D SWITCH, O/D OFF INDICATOR LIGHT CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 1 and No. 2 circuit. See CODES 6 and CODE 63 in TESTS W/CODES article.
  3. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  4. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  5. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  6. Check neutral start switch circuit. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
  7. Check O/D cancel signal circuit. See O/D CANCEL SIGNAL CIRCUIT chart in TESTS W/CODES article.
  8. Check water temperature sensor. See CODE 22 in TESTS W/CODES article.
  9. Check transmission for mechanical failure.
  10. Check ECU. See SYSTEM/COMP TESTS article.

NO DOWNSHIFT O/D To 3RD

  1. Check O/D switch and O/D OFF indicator light circuit. See O/D SWITCH, O/D OFF INDICATOR LIGHT CIRCUIT chart in TESTS W/CODES article.
  2. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  3. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  4. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  5. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  6. Check kickdown switch circuit. See CODE 68 in TESTS W/CODES article.
  7. Check transmission for mechanical failure.
  8. Check ECU. See SYSTEM/COMP TESTS article.

NO DOWNSHIFT 3RD To 2ND

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  3. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  4. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  5. Check kickdown switch circuit. See CODE 68 in TESTS W/CODES article.
  6. Check transmission for mechanical failure.
  7. Check ECU. See SYSTEM/COMP TESTS article.

NO DOWNSHIFT 2ND To 1ST

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  3. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  4. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  5. Check kickdown switch circuit. See CODE 68 in TESTS W/CODES article.
  6. Check transmission for mechanical failure.
  7. Check ECU. See SYSTEM/COMP TESTS article.

NO LOCK-UP

  1. Check solenoid No. 3 circuit. See CODE 64 in TESTS W/CODES article.
  2. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  3. Check stoplight switch circuit. See STOPLIGHT SWITCH CIRCUIT chart in TESTS W/CODES article.
  4. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  5. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  6. Check neutral start switch circuit. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
  7. Check water temperature sensor. See CODE 22 in TESTS W/CODES article.
  8. Check transmission for mechanical failure.
  9. Check ECU. See SYSTEM/COMP TESTS article.

NO LOCK-UP OFF

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 3 circuit. See CODE 64 in TESTS W/CODES article.
  3. Check stoplight switch circuit. See STOPLIGHT SWITCH CIRCUIT chart in TESTS W/CODES article.
  4. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  5. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  6. Check transmission for mechanical failure.
  7. Check ECU. See SYSTEM/COMP TESTS article.

SHIFT POINT TOO HIGH OR TOO LOW

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check pattern select switch circuit. See PATTERN SELECT SWITCH CIRCUIT chart in TESTS W/CODES article.
  3. Check speed sensor No. 1. See CODE 42 in TESTS W/CODES article.
  4. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  5. Check ECU. See SYSTEM/COMP TESTS article.

UPSHIFTS TO 2ND OR 3RD WHILE IN L RANGE

  1. Check neutral start switch circuit. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
  2. Check ECU. See SYSTEM/COMP TESTS article.

UPSHIFTS TO O/D FROM 3RD WHILE O/D SWITCH IS OFF

  1. Check O/D switch and O/D OFF indicator light circuit. See O/D SWITCH, O/D OFF INDICATOR LIGHT CIRCUIT chart in TESTS W/CODES article.
  2. Check ECU. See SYSTEM/COMP TESTS article.

UPSHIFTS TO O/D FROM 3RD WHILE ENGINE IS COLD

  1. Check O/D switch and O/D OFF indicator light circuit. See O/D SWITCH, O/D OFF INDICATOR LIGHT CIRCUIT chart in TESTS W/CODES article.
  2. Check water temperature sensor. See CODE 22 in TESTS W/CODES article.
  3. Check transmission for mechanical failure.
  4. Check ECU. See SYSTEM/COMP TESTS article.

NEUTRAL TO DRIVE

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 4 circuit. See CODE 46 in TESTS W/CODES article.
  3. Check neutral start switch circuit. See NEUTRAL START SWITCH CIRCUIT chart in TESTS W/CODES article.
  4. Check transmission for mechanical failure.
  5. Check ECU. See SYSTEM/COMP TESTS article.

LOCK-UP

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 3 circuit. See CODE 64 in TESTS W/CODES article.
  3. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  4. Check transmission for mechanical failure.
  5. Check ECU. See SYSTEM/COMP TESTS article.

ANY DRIVING RANGE

  1. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 4 circuit. See CODE 46 in TESTS W/CODES article.
  3. Check speed sensor No. 2. See CODE 61 in TESTS W/CODES article.
  4. Check O/D direct clutch speed sensor circuit. See CODE 67 in TESTS W/CODES article.
  5. Check transmission for mechanical failure.
  6. Check ECU. See SYSTEM/COMP TESTS article.

FORWARD OR REVERSE

  1. Check transmission for mechanical failure.

PARTICULAR RANGE

  1. Check transmission for mechanical failure.

NO ENGINE BRAKING

  1. Check transmission for mechanical failure.

POOR ACCELERATION

  1. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  2. Check transmission for mechanical failure.
  3. Check ECU. See SYSTEM/COMP TESTS article.

NO KICKDOWN

  1. Check kickdown switch circuit. See CODE 68 in TESTS W/CODES article.
  2. Check main throttle position sensor circuit. See MAIN THROTTLE POSITION SENSOR CIRCUIT chart in TESTS W/CODES article.
  3. Check solenoid No. 1 and No. 2 circuit. See CODE 62 and CODE 63 in TESTS W/CODES article.
  4. Check ECU. See SYSTEM/COMP TESTS article.

LARGE SHIFT SHOCK OR ENGINE STALLS WHEN STARTING OFF OR STOPPING

  1. Check stoplight switch circuit. See STOPLIGHT SWITCH CIRCUIT chart in TESTS W/CODES article.
  2. Check solenoid No. 3 circuit. See CODE 64 in TESTS W/CODES article.
  3. Check transmission for mechanical failure.
  4. Check ECU. See SYSTEM/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 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.
  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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