Engine Controls - Tests W/o Codes - Gasoline Dodge Cab & Chassis R2500

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform basic diagnostic procedures in the appropriate BASIC DIAGNOSTIC PROCEDURES article and applicable self-diagnostic tests in the appropriate SELF-DIAGNOSTICS article. 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 Powertrain Control Module (PCM). Check with manufacturer for latest PCM application.

Symptom checks direct the technician to malfunctioning component(s) 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 problems may cause a noticeable driveability problem or cause the Malfunction Indicator Light (MIL) to illuminate on some vehicles. These test procedures should also be used if a soft (intermittent) trouble code is present, but no problem is found during self-diagnostic testing.

Note. For specific testing procedures, see appropriate SELF-DIAGNOSTICS article. For specifications, see appropriate ON-VEHICLE ADJUSTMENTS and SERVICE & ADJUSTMENT SPECIFICATIONS articles.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure basic diagnostic procedures and self-diagnostic were performed before diagnosing a symptom. Symptoms available for diagnosis are as follows

1. Hard Start
2. Starts But Stalls
3. Hesitation Or Stumble
4. Surging
5. Lack Of Power
6. Knocking
7. Engine Misfire
8. Backfire
9. Rough Or Erratic Idle
10. Poor Fuel Economy

HARD START

Check the following

1. Check secondary ignition system.
2. Check engine vacuum.
3. Check fuel pressure.
4. Check Engine Coolant Temperature (ECT) sensor calibration.
5. Check Throttle Position (TP) sensor calibration.
6. Check Manifold Absolute Pressure (MAP) calibration.
7. Check minimum idle airflow.
8. Check Idle Air Control (IAC) motor operation.
9. Check engine mechanical condition.
10. Check evaporative system.
11. Check EGR system.
12. Check coolant temperature sensor and connector.
13. Check Intake Air Temperature (IAT) sensor calibration.

STARTS BUT STALLS

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check fuel pressure.
4. Check Engine Coolant Temperature (ECT) sensor calibration.
5. Check Throttle Position (TP) sensor calibration.
6. Check Manifold Absolute Pressure (MAP) calibration.
7. Check minimum idle airflow.
8. Check Idle Air Control (IAC) motor operation.

HESITATION OR STUMBLE

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check engine vacuum.
4. Check fuel pressure.
5. Check Engine Coolant Temperature (ECT) sensor calibration.
6. Check Throttle Position (TP) sensor calibration.
7. Check Manifold Absolute Pressure (MAP) calibration.
8. Check minimum idle airflow.
9. Check oxygen sensor switching.
10. Check oxygen sensor heater.
11. Check Idle Air Control (IAC) motor operation.
12. Check engine mechanical condition.
13. Check evaporative system.
14. Check EGR system.
15. Check Intake Air Temperature (IAT) sensor calibration.
16. Check Park/Neutral Position (PNP) switch.

SURGING

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check engine vacuum.
4. Check fuel pressure.
5. Check Engine Coolant Temperature (ECT) sensor calibration.
6. Check Throttle Position (TP) sensor calibration.
7. Check Manifold Absolute Pressure (MAP) calibration.
8. Check minimum idle airflow.
9. Check oxygen sensor switching.
10. Check Idle Air Control (IAC) motor operation.
11. Check evaporative system.

LACK OF POWER

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check fuel pressure.
4. Check Engine Coolant Temperature (ECT) sensor calibration.
5. Check Throttle Position (TP) sensor calibration.
6. Check Manifold Absolute Pressure (MAP) calibration.
7. Check minimum idle airflow.
8. Check oxygen sensor switching.
9. Check Idle Air Control (IAC) motor operation.
10. Check EGR system.

KNOCKING

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check fuel pressure.
4. Check Engine Coolant Temperature (ECT) sensor calibration.
5. Check Throttle Position (TP) sensor calibration.
6. Check Manifold Absolute Pressure (MAP) calibration.
7. Check minimum idle airflow.
8. Check oxygen sensor switching.
9. Check Idle Air Control (IAC) motor operation.
10. Check evaporative system.

ENGINE MISFIRE

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check fuel pressure.
4. Check minimum idle airflow.
5. Check oxygen sensor switching.
6. Check Idle Air Control (IAC) motor operation.
7. Check EGR system.

BACKFIRE

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check fuel pressure.
4. Check Manifold Absolute Pressure (MAP) calibration.
5. Check minimum idle airflow.
6. Check oxygen sensor switching.
7. Check EGR system.

ROUGH OR ERRATIC IDLE

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check engine vacuum.
4. Check fuel pressure.
5. Check Engine Coolant Temperature (ECT) sensor calibration.
6. Check Throttle Position (TP) sensor calibration.
7. Check Manifold Absolute Pressure (MAP) calibration.
8. Check minimum idle airflow.
9. Check oxygen sensor switching.
10. Check oxygen sensor heater.
11. Check Idle Air Control (IAC) motor operation.
12. Check engine mechanical condition.
13. Check evaporative system.
14. Check EGR system.
15. Check Intake Air Temperature (IAT) motor operation.
16. Check Park/Neutral Position (PNP) switch.

POOR FUEL ECONOMY

Check the following

1. Check secondary ignition system.
2. Check PCM power and ground circuits.
3. Check engine vacuum.
4. Check fuel pressure.
5. Check Engine Coolant Temperature (ECT) sensor calibration.
6. Check Throttle Position (TP) sensor calibration.
7. Check Manifold Absolute Pressure (MAP) calibration.
8. Check minimum idle airflow.
9. Check oxygen sensor switching.
10. Check oxygen sensor heater.
11. Check Idle Air Control (IAC) motor operation.
12. Check engine mechanical condition.
13. Check evaporative system.
14. Check EGR system.
15. Check Intake Air Temperature (IAT) motor operation.
16. Check Park/Neutral Position (PNP) switch.

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. If engine is running, monitor for DTCs. Use test results to identify a faulty component or circuit.