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Home/Dodge/Ram Wagon B3500/Dodge Ram Wagon B3500 (1991-2000)/Repair manual/Testing & Diagnostics/Engine Controls - Tests W/o Codes - Cng
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Engine Controls - Tests W/o Codes - Cng Dodge Ram Wagon B3500

Testing & Diagnostics ~978 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 section before disconnecting battery.

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING - CNG and TESTS W/CODES - CNG articles (see below) in the ENGINE PERFORMANCE section. Use this article to diagnose driveability problems that exist when a hard fault code is not present.

  1. «BASIC TESTING - 5.2L CNG»(/dodge/ram-wagon-b3500/1991-2000/remont/testing-diagnostics/#engine-controls-basic-testing-52l-cng)
  2. «TESTS W/CODES - 5.2L CNG»(/dodge/ram-wagon-b3500/1991-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-52l-cng)

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

Symptom checks can direct the technician to malfunctioning components for further diagnosis. A symptom should lead to a specific component test, system test or an adjustment.

Use intermittent test procedures to locate driveability problems that do not occur when the vehicle is tested. Also use these test procedures if a soft (intermittent) trouble code was present, but no problem is found during self-diagnostic testing.

Note. For specific testing procedures, see appropriate SYSTEM/COMPONENT TESTS - 5.2L CNG article in the ENGINE PERFORMANCE section. For specifications, see ADJUSTMENTS - 5.2L CNG or SPECIFICATIONS - 5.2L CNG article in the ENGINE PERFORMANCE section.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless problem occurs while vehicle is tested. To reduce diagnostic time, ensure steps in BASIC TESTING - CNG and TESTS W/CODES - CNG articles in the ENGINE PERFORMANCE section below are performed before diagnosing a symptom.

  1. «BASIC TESTING - 5.2L CNG»(/dodge/ram-wagon-b3500/1991-2000/remont/testing-diagnostics/#engine-controls-basic-testing-52l-cng)
  2. «TESTS W/CODES - 5.2L CNG»(/dodge/ram-wagon-b3500/1991-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-52l-cng)

Following symptoms are available for diagnosis.

  1. Hard Start
  2. Starts But Stalls
  3. Engine Hesitates Or Surges
  4. Insufficient Engine Power
  5. Knocking
  6. Cuts Out Or Misses
  7. Rough Or Erratic Idle
  8. Poor Fuel Economy
  9. Excessive HC & CO

HARD START

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check engine mechanical condition.

STARTS BUT STALLS

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check engine mechanical condition.

ENGINE HESITATES OR SURGES

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check oxygen sensor heater operation.
  9. Check idle air control motor operation.
  10. Check PCM power and ground circuits.
  11. Check EGR system operation.
  12. Check engine vacuum.
  13. Check engine mechanical condition.

INSUFFICIENT ENGINE POWER

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check PCM power and ground circuits.
  9. Check EGR system operation.
  10. Check engine vacuum.
  11. Check engine mechanical condition.

KNOCKING

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check oxygen sensor heater operation.
  9. Check idle air control motor operation.
  10. Check PCM power and ground circuits.
  11. Check EGR system operation.
  12. Check for vacuum leaks.
  13. Check engine mechanical condition.

CUTS OUT OR MISSES

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check PCM power and ground circuits.
  9. Check EGR system operation.
  10. Check for vacuum leaks.
  11. Check engine mechanical condition.

ROUGH OR ERRATIC IDLE

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check oxygen sensor heater operation.
  9. Check idle air control motor operation.
  10. Check PCM power and ground circuits.
  11. Check EGR system operation.
  12. Check engine vacuum.
  13. Check engine mechanical condition.

POOR FUEL ECONOMY

  1. Check secondary ignition and timing.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check fuel injectors.
  4. Check coolant temperature sensor.
  5. Check throttle position sensor calibration.
  6. Check manifold absolute pressure sensor calibration.
  7. Check oxygen sensor operation (switching).
  8. Check oxygen sensor heater operation.
  9. Check idle air control motor operation.
  10. Check PCM power and ground circuits.
  11. Check EGR system operation.
  12. Check engine vacuum.
  13. Check engine mechanical condition.

EXCESSIVE HC & CO

  1. Check for leaky fuel injectors.
  2. Ensure fuel pressure is 90-140 psi (621-965 kPa).
  3. Check for faulty oxygen sensor.
  4. Check ignition and sensor wires for poor connection.
  5. Check crankshaft position sensor.
  6. Check for vacuum leaks.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify problem. These procedures may lead to PCM setting a fault code which may help in diagnosis.

If problem vehicle does not produce fault codes, monitor voltage or resistance values using a Digital Volt-Ohmmeter (DVOM) while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates a fault has been located.

CAUTIONDO NOT use a test light on PCM-controlled circuits.

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 conditions creating an intermittent fault, use 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.

More articles — Engine Performance