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Engine Controls - Tests W/o Codes Jeep Grand Cherokee WJ

Testing & Diagnostics ~2026 words

INTRODUCTION

CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

Before diagnosing symptoms or intermittent faults, perform steps in BASIC DIAGNOSTIC PROCEDURES article and appropriate SELF-DIAGNOSTICS article. Use this article to diagnose driveability problems existing when a hard Diagnostic Trouble Code (DTC) is not present.

Note. Some driveability problems may have been corrected by manufacturer with a revised Powertrain Control Module (PCM). Check with manufacturer for latest PCM.

Symptom checks direct 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) DTC code is present, but no problem is found during self-diagnostic testing.

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 problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC DIAGNOSTIC PROCEDURES article and appropriate SELF-DIAGNOSTICS article were performed before diagnosing a symptom. Select the symptom that most accurately describes the vehicle's driveability problem and then perform that test. If the test performed does not repair the problem, continue with the next test in sequence until the problem is found and repaired. Symptoms available for diagnosis are as follows

  1. «ENGINE DOES NOT START»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__engine-does-not-start)
  2. «HARD START»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__hard-start)
  3. «STARTS & STALLS»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__starts-stalls)
  4. «HESITATION/STUMBLE»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__hesitationstumble)
  5. «SURGE»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__surge)
  6. «LACK OF POWER/SLUGGISH»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__lack-of-powersluggish)
  7. «SPARK KNOCK/DETONATION»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__spark-knockdetonation)
  8. «CUTS OUT/MISSES»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__cuts-outmisses)
  9. «BACKFIRE»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__backfire)
  10. «RUNS ROUGH/UNSTABLE, ERRATIC IDLE»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__runs-roughunstable-erratic-idle)
  11. «POOR FUEL ECONOMY»(/jeep/grand-cherokee/wj-1998-2004/remont/testing-diagnostics/#engine-controls-tests-wo-codes__poor-fuel-economy)

ENGINE DOES NOT START

If engine cranks but does not start or engine does not start and DRB displays no response, see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.

HARD START

Check listed items as follows

  1. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  2. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  3. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  6. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.
  8. Check intake air temperature sensor. See CHECKING INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.

STARTS & STALLS

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.

HESITATION/STUMBLE

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  8. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.
  9. Check intake air temperature sensor. See CHECKING INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.

SURGE

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor calibration. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  8. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.

LACK OF POWER/SLUGGISH

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.

SPARK KNOCK/DETONATION

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  8. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.

CUTS OUT/MISSES

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  4. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.

BACKFIRE

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.

RUNS ROUGH/UNSTABLE, ERRATIC IDLE

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. Check manifold absolute pressure sensor. See CHECKING MAP SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  6. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  8. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.
  9. Check intake air temperature sensor. See CHECKING INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.

POOR FUEL ECONOMY

Check listed items as follows

  1. Check Powertrain Control Module (PCM) power and ground circuits. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in SYSTEM & COMPONENT TESTING article.
  2. Check fuel pressure. See FUEL PRESSURE TEST under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Check engine coolant temperature sensor. See CHECKING ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  4. Check throttle position sensor. See CHECKING THROTTLE POSITION SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.
  5. On models with 45RFE transmission, check minimum idle airflow. See CHECKING MINIMUM AIRFLOW under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  6. Check idle air control motor operation. See CHECKING IDLE AIR CONTROL MOTOR under IDLE CONTROL SYSTEMS in SYSTEM & COMPONENT TESTING article.
  7. Check EVAP emission system. See FUEL EVAPORATIVE SYSTEM in SYSTEM & COMPONENT TESTING article.
  8. Check intake air temperature sensor. See CHECKING INTAKE AIR TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING article.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to PCM setting a Diagnostic Trouble Code (DTC) which may help in diagnosis.

If problem vehicle does not produce DTC, 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 conditions. If engine is running, monitor for DTCs. Use test results to identify a faulty component or circuit.

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