MIL Operation
The MIL is located on the instrument panel cluster (IPC).
MIL Function
- The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
- The MIL illuminates during a bulb test and a system test.
- A DTC will be stored if a MIL is requested by the PCM.
MIL Illumination
- The MIL will illuminate with ignition switch ON and the engine not running.
- The MIL will turn OFF when the engine is started.
- The MIL will remain ON if the self-diagnostic system has detected a malfunction.
- The MIL may turn OFF if the malfunction is not present.
- If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
- If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
Test Description
The number below refers to the step number on the diagnostic table.
- 4: This step tests for a short to voltage on the MIL control circuit. With the fuse removed there should be no voltage on the MIL control circuit.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Verify whether the instrument cluster is operational. If the instrument panel (IP) is completely inoperative, refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages and Console. Command the MIL ON and OFF with a scan tool. Does the MIL turn ON and OFF when commanded with a scan tool? | Go to Intermittent Conditions | Go to Step 3 | |
| 3 | Inspect the fuse that supplies ignition voltage to the cluster. Is the fuse open? | Go to Step 10 | Go to Step 4 | |
| 4 | Turn OFF the ignition. Remove the fuse that supplies voltage to the cluster. Disconnect the powertrain control module (PCM). Turn ON the ignition with the engine OFF. Measure the voltage from the MIL control circuit in the PCM harness connector to a good ground. Is the voltage less than the specified value? | 0.3 V | Go to Step 5 | Go to Step 11 |
| 5 | Turn OFF the ignition. Install the fuse that supplies voltage to the cluster. Turn ON the ignition with the engine OFF. Connect a 3-amp fused jumper wire between the MIL control circuit in the PCM harness connector and a good ground. Is the MIL illuminated? | Go to Step 9 | Go to Step 6 | |
| 6 | Turn OFF the ignition. Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Probe the ignition voltage circuit of the IPC harness connector with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 7 | Go to Step 12 | |
| 7 | Test the MIL control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | Go to Step 15 | Go to Step 8 | |
| 8 | Test for an intermittent and for a poor connection at the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 13 | |
| 9 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 | |
| 10 | Repair the short to ground in the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 11 | Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 12 | Repair the open in the ignition voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 13 | Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 15 | ||
| 14 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 15 | ||
| 15 | Turn OFF the ignition for 30 seconds. Does the vehicle operate correctly, without any MIL illumination and without any stored DTCs? | System OK | Go to Diagnostic Trouble Code (DTC) List | |
Malfunction Indicator Lamp (MIL) Inoperative
The MIL is located on the instrument panel (IPC).
MIL Function
- The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
- The MIL illuminates during a bulb test and a system test.
- A DTC will be stored if a MIL is requested by the diagnostic.
MIL Illumination
- The MIL will illuminate with ignition switch ON and the engine not running.
- The MIL will turn OFF when the engine is started.
- The MIL will remain ON if the self-diagnostic system has detected a malfunction.
- The MIL may turn OFF if the malfunction is not present.
- If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
- If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.
The number below refers to the step number on the diagnostic table.
- 2: This step determines if the condition is with the MIL control circuit or the PCM.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | Turn OFF the ignition. Disconnect the PCM. Turn ON the ignition, with the engine OFF. Observe the MIL. Is the MIL illuminated? | Go to Step 3 | Go to Step 5 |
| 3 | Remove the instrument panel cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Test the MIL control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
| 4 | Replace the IPC. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | Go to Step 6 | |
| 5 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 6 | |
| 6 | Turn the ignition OFF for 30 seconds. Start the engine. Does the vehicle operate correctly without any MIL illumination, and without any stored DTCs? | System OK | Go to Diagnostic System Check - Engine Controls |
Malfunction Indicator Lamp (MIL) Always On
Description
The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that prevents an engine from starting. The Engine Cranks but Does Not Run diagnostic table directs the service technician to the appropriate system diagnosis.
The Engine Cranks but Does Not Run diagnostic table assumes the following
- The battery is completely charged. Refer to «Battery Inspection/Test (Non-HP2)»(ref-184152-S28156847602005082200000) or «Battery Inspection/Test (HP2)»(ref-184152-S41639296552005082200000) in Engine Electrical.
- The cranking speed is acceptable. Refer to «Engine Cranks Slowly»(ref-184152-S21837754192005082200000) in Engine Electrical.
- There is adequate fuel in the fuel tank.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Turn ON the ignition, with the engine OFF. Observe the DTC information with a scan tool. Does the scan tool display DTC P0230, P0335, P0336, P0601, P0602, P0604, P1626, P1631, or P1683? | Go to Diagnostic Trouble Code (DTC) List | Go to Step 3 | |
| 3 | Does the scan tool display any body control module (BCM) vehicle theft deterrent (VTD) DTCs? | Go to Diagnostic System Check - Theft Deterrent in Theft Deterrent | Go to Step 4 | |
| 4 | Probe both sides of the following fuses with a test lamp that is connected to a good ground: ECM 1 INJ A INJ B Does the test lamp illuminate on at least one side of all of the fuses? | Go to Step 5 | Go to Ignition Relay Diagnosis | |
| 5 | Attempt to start the engine. Observe the Engine Speed parameter with a scan tool, while the engine is cranking. Does the engine speed increment? | Go to Step 6 | Go to Distributor Ignition (DI) System Diagnosis | |
| 6 | Monitor the Ignition 1 Signal Voltage parameter with a scan tool. Is the Ignition 1 Signal Voltage parameter at the specified value? | B+ | Go to Step 7 | Go to Step 11 |
| 7 | Command the fuel pump ON with a scan tool. Does the fuel pump turn ON? | Go to Step 8 | Go to Fuel Pump Electrical Circuit Diagnosis | |
| 8 | Turn OFF the ignition. Disconnect a spark plug wire. Install the J 26792 spark tester to the spark plug wire. Attempt to start the engine. Does the spark tester spark? | Go to Step 9 | Go to Distributor Ignition (DI) System Diagnosis | |
| 9 | Turn OFF the ignition. Install the J 34730-1A fuel pressure gage. Refer to Fuel System Diagnosis . Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Is the fuel pressure within the specified range while the fuel pump is operating? | 379-427 kPa (55-62 psi) | Go to Step 10 | Go to Fuel System Diagnosis |
| 10 | Inspect for the following conditions: A collapsed air intake duct A restricted air filter element-Refer to Air Cleaner Element Replacement . The spark plugs for being gas or coolant fouled-Refer to Spark Plug Inspection . If the spark plugs are fouled, determine what caused the condition. Any engine mechanical condition, such as a worn timing chain, gears and low compression-Refer to Symptoms - Engine Mechanical in Engine Mechanical 4.3L. A restricted exhaust system-Refer to Restricted Exhaust in Engine Exhaust. The engine coolant temperature (ECT) sensor is NOT close to the actual engine temperature. Refer to DTC P0125 . Compare manifold absolute pressure/barometric pressure (MAP/BARO) parameters to another vehicle. The parameters should be close in value. Refer to DTC P0106 . The throttle position (TP) sensor for being stuck in range-Refer to DTC P0121 . Did you find complete the action? | Go to Step 14 | ||
| 11 | Test the ignition 1 signal voltage circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the fuse if necessary. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 | |
| 12 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 | |
| 13 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 14 | ||
| 14 | Clear the DTCs with a scan tool. Attempt to start the engine. Does the engine start and continue to operate? | Go to Step 15 | Go to Step 2 | |
| 15 | Idle the engine. Allow the engine to reach operating temperature. Observe the DTC information with a scan tool. Are any DTCs displayed? | Go to Diagnostic Trouble Code (DTC) List | System OK | |
Engine Cranks but Does Not Run
System Description
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected and the ignition remains ON.
The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | IMPORTANT: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Does the fuel pump operate? | Go to Step 3 | Go to Fuel Pump Electrical Circuit Diagnosis | |
| 3 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage with the fuel pump commanded ON. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 4 | Go to Step 10 |
| 4 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Step 8 | Go to Step 5 |
| 5 | Relieve the fuel pressure to the first specified value. Monitor the fuel pressure gage for 5 minutes. Does the fuel pressure decrease by more than the second specified value? | 69 kPa (10 psi) 14 kPa (2 psi) | Go to Step 22 | Go to Step 6 |
| 6 | Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gage. Start the engine. Does the fuel pressure decrease by the specified value when the engine is started? | 21-69 kPa (3-10 psi) | Go to Step 7 | Go to Step 21 |
| 7 | Operate the vehicle within the conditions of the customer's concern. Monitor the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? | Go to Step 15 | Go to Symptoms - Engine Controls | |
| 8 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement . Disconnect the rear fuel feed pipe and the rear fuel return pipe from the chassis fuel pipes. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Drain any remaining fuel into an approved gasoline container. Install the J 37287 fuel line shut-off adapters between the rear fuel pipes and the chassis fuel pipes. Open the valves on the fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Bleed the air from the fuel pressure gage. Command the fuel pump relay ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure remain constant? | Go to Step 17 | Go to Step 9 | |
| 9 | Turn OFF the ignition. Open the fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gage for 1 minute. Does the fuel pressure remain constant? | Go to Step 21 | Go to Step 18 | |
| 10 | Is the fuel pressure more than the specified value? | 427 kPa (62 psi) | Go to Step 12 | Go to Step 11 |
| 11 | Is the fuel pressure more than the specified value? | 0 kPa (0 psi) | Go to Step 14 | Go to Step 15 |
| 12 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement . Disconnect the rear fuel return pipe from the chassis pipe. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Attach a length of flexible hose to the chassis fuel pipe. Place the open end of the flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gage while the fuel pump is operating. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 20 | Go to Step 13 |
| 13 | Inspect the engine fuel return pipe and the chassis fuel return pipe for a restriction. Did you find and correct the condition? | Go to Step 23 | Go to Step 21 | |
| 14 | Turn OFF the ignition. Relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure . Remove the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement . Disconnect the rear fuel return pipe from the chassis pipe. Refer to Quick Connect Fitting(s) Service (Plastic Collar) . Install the J 37287 between the rear fuel return pipe and the chassis fuel pipe. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Bleed the air from the fuel pressure gage. Monitor the fuel pressure gage. NOTE: DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system. Command the fuel pump relay ON with a scan tool. Slowly close the valve in the fuel return pipe shut-off adapter, while the fuel pump is operating. Does the fuel pressure increase to more than the specified value? | 427 kPa (62 psi) | Go to Step 21 | Go to Step 15 |
| 15 | Inspect the following components for a restriction: The fuel filter The fuel feed pipe Did you find and correct the condition? | Go to Step 23 | Go to Step 16 | |
| 16 | Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 23 | Go to Step 17 | |
| 17 | Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement . Inspect the following items: The fuel pump flex hose for damage The in-tank fuel pump harness connectors for poor connections The fuel strainer for a restriction The fuel tank for contaminants Did you find and correct the condition? | Go to Step 23 | Go to Step 22 | |
| 18 | Open the fuel return pipe shut-off valve. Remove the upper intake manifold. Refer to Intake Manifold Replacement - Upper in Engine Mechanical-4.3L. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body. Turn ON the ignition, with the engine OFF. Inspect for a fuel leak from the fuel pressure regulator. Is the fuel pressure regulator leaking fuel? | Go to Step 21 | Go to Step 19 | |
| 19 | Remove the fuel injectors from the intake manifold in order to isolate the leaking fuel injector. Refer to Fuel Injector Replacement . Did you complete the replacement? | Go to Step 23 | ||
| 20 | Repair the restricted fuel return pipe between the chassis fuel pipe and the fuel tank. Did you complete the repair? | Go to Step 23 | ||
| 21 | IMPORTANT: Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator. Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .Did you complete the replacement? | Go to Step 23 | ||
| 22 | Replace the fuel sender. Refer to Fuel Sender Assembly Replacement . Did you complete the replacement? | Go to Step 23 | ||
| 23 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| NOTE |
|---|
| DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system. |
| IMPORTANT |
|---|
| Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator. |
Fuel System Diagnosis
The scan tool is first used to energize the fuel pump relay. The fuel injector tester is then used to pulse each injector for a precise amount of time, allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
| Cylinder | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1st Reading | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) |
| 2nd Reading | 310 kPa (45 psi) | 296 kPa (43 psi) | 303 kPa (44 psi) | 324 kPa (47 psi) |
| Amount of Drop | 83 kPa (12 psi) | 97 kPa (14 psi) | 90 kPa (13 psi) | 69 kPa (10 psi) |
| Average Range: 75-95 kPa (10.9-13.8 psi) | Injector OK | Replace fuel injector - too much fuel pressure drop | Injector OK | Replace fuel injector - too little fuel pressure drop |
Fuel Injector Balance Test Example (Typical)
The number below refers to the step number on the diagnostic table.
- 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Did you perform the Fuel Injector Coil Test? | Go to Step 3 | Go to Fuel Injector Coil Test | |
| 3 | IMPORTANT: DO NOT perform this test if the engine coolant temperature (ECT) is above 94° C (201° F). Observe the ECT Sensor parameter with a scan tool.Is the ECT Sensor parameter less than the specified value? | 94° C (201° F) | Go to Step 4 | |
| 4 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage, with the fuel pump operating. Is the fuel pressure within the specified range? | 379-427 kPa (55-62 psi) | Go to Step 5 | Go to Fuel System Diagnosis |
| 5 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 6 |
| 6 | NOTE: Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding. Disconnect the multi-way harness connector of the fuel injectors. Connect the J 39021 Fuel Injector Tester, J 39021 - 210 Injector Selector Switch Box, and the J 39021-301 Injector Test Adapter to the fuel meter body. Set the amperage supply selector switch on the fuel injector tester to the Balance Test 0.5-2.5 amp position. Command the fuel pump relay ON and then OFF with a scan tool. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the first pressure reading. IMPORTANT: The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the fuel injector by depressing the Push to Start Test button on the fuel injector tester. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the second pressure reading. Repeat steps 4 through 7 for each fuel injector. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Is the difference between any individual pressure drop and the average pressure drop more than the specified value? | 10 kPa (1.5 psi) | Go to Step 7 | Go to Symptoms - Engine Controls |
| 7 | Clean the fuel injectors. Refer to Fuel Injector Cleaning Procedure . Did you complete the action? | Go to Step 8 | ||
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Symptoms - Engine Controls |
| IMPORTANT |
|---|
| DO NOT perform this test if the engine coolant temperature (ECT) is above 94° C (201° F). |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times, in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| NOTE |
|---|
| Do Not repeat any portion of this test before running the engine in order to prevent the engine from flooding. |
| IMPORTANT |
|---|
| The fuel pressure may rise after the fuel injector stops pulsing. Record the fuel pressure value immediately after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. |
Fuel Injector Balance Test with Special Tool
The scan tool is first used to energize the fuel pump relay. The scan tool is then used to pulse each injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in system fuel pressure that can be recorded and used to compare each injector.
| Cylinder | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1st Reading | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) | 393 kPa (57 psi) |
| 2nd Reading | 310 kPa (45 psi) | 296 kPa (43 psi) | 303 kPa (44 psi) | 324 kPa (47 psi) |
| Amount of Drop | 83 kPa (12 psi) | 97 kPa (14 psi) | 90 kPa (13 psi) | 69 kPa (10 psi) |
| Average Range: 75-95 kPa (10.9-13.8 psi) | Injector OK | Replace fuel injector - too much fuel pressure drop | Injector OK | Replace fuel injector - too little fuel pressure drop |
Fuel Injector Balance Test Example (Typical)
The number below refers to the step number on the diagnostic table.
- 3: The engine coolant temperature (ECT) must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Did you perform the Fuel Injector Coil Test? | Go to Step 3 | Go to Fuel Injector Coil Test | |
| 3 | IMPORTANT: DO NOT perform this test if the engine coolant temperature (ECT) is above 94° C (201° F). Observe the ECT Sensor parameter with a scan tool.Is the ECT Sensor parameter less than the specified value? | 94° C (201° F) | Go to Step 4 | |
| 4 | IMPORTANT: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal . Turn ON the ignition, with the engine OFF. IMPORTANT: The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gage, with the fuel pump operating. Is the fuel pressure within the specified value? | 379-427 kPa (55-62 psi) | Go to Step 5 | Go to Fuel System Diagnosis |
| 5 | IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Monitor the fuel pressure gage for 1 minute.Does the fuel pressure decrease by more than the specified value? | 34 kPa (5 psi) | Go to Fuel System Diagnosis | Go to Step 6 |
| 6 | With a scan tool, select the Fuel Injector Balance Test function, within the Special Functions menu. Select an injector to be tested. Press Enter. This will prime the fuel system. Record the fuel pressure indicated by the fuel pressure gage after the fuel pressure stabilizes. This is the 1st pressure reading. IMPORTANT: Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. Energize the fuel injector by depressing the Pulse Injector button on the scan tool. This will energize the injector and decrease the fuel pressure. Record the fuel pressure indicated by the fuel pressure gage after the fuel injector has stopped pulsing. This is the 2nd pressure reading. Press Enter again to bring you back to the Select Injector screen. Repeat for each fuel injector. Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value. Obtain a pressure drop value for each fuel injector. Add all of the individual pressure drop values. This is the total pressure drop. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. Is the difference between any individual pressure drop and the average pressure drop more than the specified value? | 10 kPa (1.5 psi) | Go to Step 7 | Go to Symptoms - Engine Controls |
| 7 | Clean the fuel injectors. Refer to Fuel Injector Cleaning Procedure . Did you complete the action? | Go to Step 8 | ||
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Symptoms - Engine Controls |
| IMPORTANT |
|---|
| DO NOT perform this test if the engine coolant temperature (ECT) is above 94° C (201° F). |
| IMPORTANT |
|---|
| Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic. |
| IMPORTANT |
|---|
| The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. DO NOT start the engine. |
| IMPORTANT |
|---|
| The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. |
| IMPORTANT |
|---|
| Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value. |
Fuel Injector Balance Test with Tech 2
The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected, if more than the calibrated amount, when the evaporative emission (EVAP) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics have failed two test cycles.
The numbers below refer to the step numbers on the diagnostic table.
- 4: This step tests for fuel leaks below the fuel tank fuel level.
- 5: This step tests for fuel vapors escaping above the fuel level in the fuel tank.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | CAUTION: Gasoline or gasoline vapors are highly flammable. A fire could occur if an ignition source is present. Never drain or store gasoline or diesel fuel in an open container, due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect the fuel tank and the fuel pipes for damage or external leaks. Did you find fuel leaking from the fuel tank? | Go to Step 6 | Go to Step 3 |
| 3 | Turn ON the ignition, with the engine OFF. Command the fuel pump relay ON with a scan tool. Inspect for fuel leaking from the fuel pipes. Did fuel leak from the fuel pipes? | Go to Step 7 | Go to Step 4 |
| 4 | Turn OFF the ignition. Install the J 41413-200 Evaporative Emissions System Tester (EEST) and the J 41415-40 Fuel Tank Cap Adapter or the GE-41415-50 Interrupted Thread Fuel Tank Cap Adapter. IMPORTANT: If the floating indicator registers any flow after stabilizing, a leak is evident. Test for a fuel tank leak referring to the J 41413-210 Operation Manual. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information. Inspect for a fuel leak while the system is under pressure. Did fuel leak from the fuel tank? | Go to Step 6 | Go to Step 5 |
| 5 | Using the J 41413-200 and the J 41413-210 Operation Manual, introduce smoke into the evaporative emission (EVAP) system. IMPORTANT: It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement . Inspect for leaks in any of the following locations: The fuel tank, fill limiter vent valve, pressure relief valve and the grade vent valves-Refer to Fuel Tank Replacement . The fuel sender housing and fuel sender seal-Refer to Fuel Sender Assembly Replacement . The fuel tank pressure (FTP) sensor seal-Refer to Fuel Tank Pressure Sensor Replacement . The EVAP pipes-Refer to Evaporative Emission (EVAP) Hoses/Pipes Replacement - Canister/Fuel Tank . The fuel fill pipe and hose-Refer to Filler Tube Replacement . Did you find and correct the condition? | Go to Step 8 | Go to Diagnostic Aids |
| 6 | Replace the fuel tank. Refer to Fuel Tank Replacement . Did you complete the repair? | Go to Step 8 | |
| 7 | Replace the leaking fuel pipe. Refer to Fuel Hose/Pipes Assembly Replacement . Did you complete the replacement? | Go to Step 8 | |
| 8 | Operate the system under the condition of the customer concern in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
| CAUTION |
|---|
| Gasoline or gasoline vapors are highly flammable. A fire could occur if an ignition source is present. Never drain or store gasoline or diesel fuel in an open container, due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby. |
| IMPORTANT |
|---|
| If the floating indicator registers any flow after stabilizing, a leak is evident. |
| IMPORTANT |
|---|
| It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement . |
Fuel Tank Leak Test
Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.
Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling, or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components, and fuel filter restriction.
Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start, or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel injection system, and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the fuel system components for rust or deterioration.
Ethanol concentrations of greater than 10 percent can cause driveability conditions and fuel system deterioration. Fuel with more than 10 percent ethanol could result in driveability conditions such as hesitation, lack of power, stalling, or no start. Excessive concentrations of ethanol used in vehicles not designed for it may cause fuel system corrosion, deterioration of rubber components, and fuel filter restriction.
The numbers below refer to the step numbers on the diagnostic table.
- 5: This test will determine the ability of the PCM and IAC valve control circuits to control the IAC valve.
- 7: This test will determine the ability of the PCM to provide the IAC control valve circuits with a ground. On a normally operating system, the test lamp should not flash while the IAC Counts are incriminating.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | IMPORTANT: Ensure that the Engine Speed parameter stabilizes with each Commanded RPM change to determine if the engine speed stays within 100 RPM less than the Commanded RPM or within 200 RPM more than the Commanded RPM. Set the parking brake and block the drive wheels. Start the engine. Turn OFF all accessories. Slowly increment the engine speed to 1,700 RPM, then to 600 RPM, then to 1,700 RPM with the scan tool RPM Control function. Exit the RPM Control function. Did the Engine Speed parameter stabilize within 100 RPM less than the commanded engine speed or within 200 RPM above the Commanded RPM? | Go to Diagnostic Aids | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the IAC valve. Connect an J 37027-1A IAC Motor Driver to the IAC valve. Start the engine. Command the IAC valve in until 600 RPM is reached with the J 37027-1A . Command the IAC valve out until 1,700 RPM is reached with the J 37027-1A . Return the engine speed to the Desired Idle Speed parameter. Did the Engine Speed parameter steadily decrease to 600 RPM and steadily increase to 1,700 RPM when the IAC valve was commanded in and out? | Go to Step 5 | Go to Step 4 |
| 4 | Did you observe an excessively high idle condition that could not be controlled with the IAC motor driver? | Go to Step 11 | Go to Step 12 |
| 5 | Connect a test lamp between one of the IAC valve control circuits and a good ground. Start the engine. Observe the IAC Counts parameter with a scan tool. Command high RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Command low RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Return the Engine Speed to the Desired Idle Speed parameter. Repeat the above procedure for the other three IAC valve control circuits. Did the test lamp remain ON, never flashing, while the IAC Counts were incriminating for any of the IAC valve control circuits? | Go to Step 10 | Go to Step 6 |
| 6 | Did the test lamp remain OFF, never flashing, while the IAC Counts were incriminating for any of the IAC valve control circuits? | Go to Step 9 | Go to Step 7 |
| 7 | Connect a test lamp between the IAC coil A low control circuit and the IAC coil A high control circuit. Observe the IAC Counts parameter with a scan tool and the test lamp. Command high RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Command low RPM with the J 37027-1A until the IAC Counts parameter starts to increment. Return the Engine Speed parameter to the Desired Idle Speed parameter. Repeat the above procedure with the test lamp connected between the IAC coil B low control circuit and the IAC coil B high control circuit. Did the test lamp stay illuminated, never flashing, while the IAC Counts were incriminating? | Go to Step 8 | Go to Step 17 |
| 8 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 9 | Turn OFF the ignition. Disconnect the PCM. Test the circuit where the test lamp remained OFF for the following conditions: An open circuit A short to ground A short to another IAC valve control circuit-Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 10 | Turn ON the ignition. Test the IAC valve control circuit where the test lamp remained illuminated for the following conditions: A short to voltage A short to another IAC valve control circuit- Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 |
| 11 | Inspect for the following: Throttle body damage and tampering Skewed TP sensor signal Throttle lever screw tampering, if equipped Vacuum leaks Faulty, incorrectly installed PCV valve and hose, if equipped Throttle shaft binding Throttle linkage or cruise control linkage binding, if equipped Remove the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Inspect for the following conditions: Debris in the IAC passage Excessive deposits on the throttle plate Excessive deposits in the throttle bore Excessive deposits on IAC valve pintle Did you find and correct the condition? | Go to Step 18 | Go to Step 15 |
| 12 | Inspect for the following conditions: Throttle body damage and tampering Throttle lever screw tampering, if equipped Excessive deposits on the throttle plate Restricted air intake system-Inspect the following conditions: A possible collapsed or clogged air intake duct, before and after the air filter element A restricted air filter element Restriction at the throttle body intake screen, if equipped Remove the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Inspect for excessive deposits on the IAC valve pintle and in the IAC valve passage. Did you find and correct the condition? | Go to Step 18 | Go to Step 15 |
| 13 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 14 |
| 14 | Disconnect the PCM. Test all IAC valve control circuits for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 17 |
| 15 | Test for an intermittent and for a poor connection at the IAC valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 16 |
| 16 | Replace the IAC valve. Refer to Idle Air Control (IAC) Valve Replacement . Did you complete the replacement? | Go to Step 18 | |
| 17 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 18 | |
| 18 | Reassemble the vehicle as necessary. Clear any DTCs with a scan tool. Start the engine. Operate the system to verify the repair. Did you correct the condition? | Go to Step 19 | Go to Step 2 |
| 19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Ensure that the Engine Speed parameter stabilizes with each Commanded RPM change to determine if the engine speed stays within 100 RPM less than the Commanded RPM or within 200 RPM more than the Commanded RPM. |
Idle Air Control (IAC) System Diagnosis
This system includes the crankshaft position (CKP) sensor, the camshaft position (CMP) sensor, the ignition coil with the ignition control (IC) module, the secondary wires, the spark plugs, and the circuit conductors and connectors.
The powertrain control module (PCM) controls the ignition system. The PCM monitors the input signals from various engine sensors. The PCM controls the dwell of the ignition primary coil, computes the desired spark timing and firing of the ignition system via an IC timing control circuit to the ignition control module.
The Distributor Ignition (DI) System Diagnostic Table assumes the following conditions
- The battery is fully charged.
- There is adequate fuel in the fuel tank.
- The fuel delivery system is functional.
The numbers below refer to the step numbers on the diagnostic table.
- 3: This step is testing for a crankshaft position sensor (CKP) signal to the PCM.
- 4: This step is testing for an internally shorted camshaft position sensor.
- 9: This step is testing for spark output at more than one spark plug wire. The J-26792 requires a minimum of 25,000 volts to operate.
- 10: This step determines if spark is being delivered to the distributor cap.
- 20: This test is testing if the PCM is providing a timing control signal to the ignition control module.
- 21: This test checks for a basic engine mechanical problem.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views | ||||
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls | |
| 2 | Test the fuse which supplies ignition 1 voltage to the ignition coil assembly and the ignition control module (ICM). Refer to Circuit Protection - Fuses in Wiring Systems. Is the fuse open? | Go to Step 32 | Go to Step 3 | |
| 3 | Observe the engine speed parameter with a scan tool. Crank the engine. Is the engine speed parameter more than the specified value? | 125 RPM | Go to Step 9 | Go to Step 4 |
| 4 | Turn OFF the ignition. Disconnect the camshaft position (CMP) sensor electrical connector. Attempt to start the engine. Does the engine start and continue to run? | Go to Step 26 | Go to Step 5 | |
| 5 | Turn ON the ignition with the engine OFF. Measure the voltage of the 12-volt reference circuit of the CMP sensor to a good ground with a DMM. Refer to Measuring Voltage in Wiring Systems. Is the voltage equal the specified value? | B+ | Go to Step 6 | Go to Step 8 |
| 6 | Turn OFF the ignition. Disconnect the crankshaft position (CKP) sensor electrical connector. Turn ON the ignition with the engine OFF Measure the voltage from the 12-volt reference circuit of the CKP sensor to a good ground with a DMM. Refer to Measuring Voltage in Wiring Systems Is the voltage equal the specified value? | B+ | Go to Step 27 | Go to Step 7 |
| 7 | Turn OFF the ignition. Test the CKP 12-volt reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 8 | |
| 8 | Turn OFF the ignition. Test the CMP 12-volt reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 30 | |
| 9 | Turn OFF the ignition. Disconnect a spark plug wire from a spark plug. Install the J 26792 Spark Tester into the spark plug wire end and attach the clamp end to a good engine ground. IMPORTANT: A few sparks then nothing is considered no spark. Observe the J 26792 . Crank the engine. If there is no spark on one wire, test a second wire. Does multiple spark events occur on both spark plug wires? | Go to Step 31 | Go to Step 10 | |
| 10 | Disconnect the ignition coil wire from the distributor cap. Install the J 26792 into the ignition coil wire end and clamp the spark tester to a good engine ground. Observe the J 26792 . Crank the engine. Does multiple spark events occur? | Go to Step 21 | Go to Step 11 | |
| 11 | Disconnect the ignition coil wire from the ignition coil. Measure the ignition coil wire resistance. Is the resistance less than the specified value? | 1,000 ohm/ft | Go to Step 12 | Go to Step 44 |
| 12 | Turn OFF the ignition. Disconnect the ignition coil electrical connector. Probe the ignition coil control circuit of the ignition coil with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Crank the engine. Does the test lamp flash while cranking the engine? | Go to Step 15 | Go to Step 13 | |
| 13 | Turn OFF the ignition. Probe the ignition coil control circuit of the ignition coil with a test lamp connected to battery voltage. Does the test lamp illuminate? | Go to Step 14 | Go to Step 16 | |
| 14 | Turn OFF the ignition. Disconnect the ignition control module electrical connector. Probe the ignition coil control circuit of the ignition coil with a test lamp connected to battery voltage. Does the test lamp illuminate? | Go to Step 40 | Go to Step 47 | |
| 15 | Turn ON the ignition with the engine OFF. Measure the voltage from the ignition 1 voltage circuit of the ignition coil to a good ground with a DMM. Is the voltage more than the specified value? | 10 V | Go to Step 29 | Go to Step 33 |
| 16 | Turn OFF the ignition. Disconnect the ignition control module electrical connector. Turn ON the ignition with the engine OFF. Probe the ignition coil control circuit of the ignition control module with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 39 | Go to Step 17 | |
| 17 | Turn OFF the ignition. Test the ignition coil control circuit between the ignition coil and the ignition module for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 18 | |
| 18 | Turn ON the ignition with the engine OFF. Measure the voltage from the ignition 1 voltage circuit of the ignition control module to a good ground with a DMM. Is the voltage more than the specified value? | 10 V | Go to Step 19 | Go to Step 34 |
| 19 | Probe the ground circuit of the ignition control module with a test lamp that is connected to battery voltage. Does the test lamp illuminate? | Go to Step 20 | Go to Step 35 | |
| 20 | Measure the voltage from the IC timing control circuit of the ignition control module to a good ground with a DMM. Observe the voltage on the DMM. Crank the engine. Is the voltage within the specified value? | 1-4 V | Go to Step 28 | Go to Step 23 |
| 21 | Remove the distributor cap. Inspect inside the distributor cap for damage or contamination. Refer to Distributor Inspection . Did you find a condition? | Go to Step 46 | Go to Step 22 | |
| 22 | Observe the distributor rotor. Crank the engine. Does the distributor rotor rotate when the engine cranks? | Go to Step 45 | Go to Diagnostic Aids | |
| 23 | Turn OFF the ignition. Disconnect the PCM electrical connectors. Test the IC timing control circuit for an open or a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 24 | |
| 24 | Probe the IC timing control circuit of the PCM with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | Go to Step 37 | Go to Step 25 | |
| 25 | Turn ON the ignition with the engine OFF. Probe the IC timing control circuit of the PCM with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | Go to Step 38 | Go to Step 30 | |
| 26 | Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 41 | |
| 27 | Test for an intermittent and for a poor connection at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 42 | |
| 28 | Test for an intermittent and for a poor connection at the ignition control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 47 | |
| 29 | Test for an intermittent and for a poor connection at the ignition coil. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 43 | |
| 30 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 50 | Go to Step 48 | |
| 31 | Inspect the spark plugs for damage or contamination. Refer to Spark Plug Replacement and Spark Plug Inspection . Did you find and correct the condition? | Go to Step 50 | Go to Intermittent Conditions | |
| 32 | Repair the short to ground in the ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 49 | ||
| 33 | Repair the open or the high resistance in the ignition 1 voltage circuit between the underhood fuse block and the ignition coil. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 34 | Repair the open or the high resistance in the ignition 1 voltage circuit between the underhood fuse block and the ignition control module. Did you complete the repair? | Go to Step 50 | ||
| 35 | Repair the open or the high resistance in the ground circuit of the ignition control module. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 36 | Repair the open or the high resistance in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 37 | Repair the short to ground in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 38 | Repair the short to voltage in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 39 | Repair the short to voltage in the ignition coil control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 40 | Repair the short to ground in the ignition coil control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 50 | ||
| 41 | Replace the CMP sensor. Refer to Camshaft Position (CMP) Sensor Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 42 | Replace the CKP sensor. Refer to Crankshaft Position (CKP) Sensor Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 43 | Replace the ignition coil. Refer to Ignition Coil(s) Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 44 | Replace the ignition coil wire. Refer to Spark Plug Wire Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 45 | Replace the distributor rotor. Refer to Distributor Overhaul . Did you complete the replacement? | Go to Step 50 | ||
| 46 | Replace the distributor cap. Refer to Distributor Overhaul . Did you complete the replacement? | Go to Step 50 | ||
| 47 | Replace the ignition control module. Refer to Ignition Control Module Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 48 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement? | Go to Step 50 | ||
| 49 | Replace the fuse. Did you complete the replacement? | Go to Step 50 | ||
| 50 | Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle for 5 minutes. Does the vehicle operate normally with no malfunction indicator lamp (MIL) illumination and no stored DTCs? | System OK | Go to Diagnostic Trouble Code (DTC) List | |
| IMPORTANT |
|---|
| A few sparks then nothing is considered no spark. |
Distributor Ignition (DI) System Diagnosis
Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the I/M emission inspection in order to renew license plates. This is accomplished by viewing the I/M System Status display on a scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that the vehicle meets the criteria that comply with the local area requirements.
The purpose of the I/M Complete System Set Procedure is to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform this test when more than one of the I/M System Status indicators are set to NO.
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step runs the HO2S Heater Tests and initiate the EVAP System Test. Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria.
- 3: This step runs the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. The Oxygen Sensor Tests begin once the engine is at operating temperature, in Closed Loop Fuel Control, and a calibrated amount of time has elapsed.
- 5: This step runs the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Did you perform the Inspection/Maintenance (I/M) System Check? | Go to Step 2 | Go to Inspection/Maintenance (I/M) System Check | |
| 2 | IMPORTANT: Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. Once the engine is started, DO NOT turn the engine OFF for the remaining portion of the set procedure. Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Set the vehicle parking brake. Verify the transmission is in PARK for automatic transmissions. Start the engine. Allow the engine to idle for the specified time. Is the action complete? | 2 minutes | Go to Step 3 | |
| 3 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 90 km/h (55 mph) with this speed maintained until the engine reaches operating temperature. This may be up to 10 minutes depending on the start up coolant temperature. Continued operation under these conditions for an additional 6 minutes. Is the action complete? | Go to Step 4 | ||
| 4 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Vehicle speed reduced to 72 km/h (45 mph) with this speed maintained for one additional minute. Four decelerations of 25 seconds each from 72 km/h (45 mph) while the following criteria is maintained: Throttle is closed NO brake application NO manual downshift Vehicle speed remains above 40 km/h (25 mph). After each deceleration period, vehicle is returned to 72 km/h (45 mph) under part throttle acceleration and speed is maintained for 15 seconds. Is the action complete? | Go to Step 5 | ||
| 5 | CAUTION: Refer to Road Test Caution in Cautions and Notices. In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 75-89 km/h (45-55 mph) with this speed maintained for 2 minutes Decelerate to 0 km/h (0 mph) Idle the engine for 2 minutes while the following criteria is maintained: Service brake is pressed. Automatic transmission is in DRIVE. Is the action complete? | Go to Step 6 | ||
| 6 | Observe the I/M System Status display with a scan tool. Did all of the I/M System Status indicators update to YES? | Go to Step 7 | Go to the I/M System Set Procedure for the indicated systems that have not updated | |
| 7 | Observe the Emission Related DTC portion of the I/M System Status display with a scan tool. Does the scan tool indicate any Emission Related DTCs set? | Go to Diagnostic Trouble Code (DTC) List | System OK |
| IMPORTANT |
|---|
| Whenever the ignition is turned ON, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn OFF the ignition for approximately 5 minutes to allow the sensors to cool before continuing with the test. Once the engine is started, DO NOT turn the engine OFF for the remaining portion of the set procedure. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
| CAUTION |
|---|
| Refer to Road Test Caution in Cautions and Notices. |
Inspection/Maintenance (I/M) Complete System Set Procedure
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Catalyst System. The test may be used to set the I/M System Status indicators to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the evaporative emission (EVAP) system. The test may be used to set the I/M System Status indicators to YES. The I/M System Status Display on the scan tool provides an indication of when the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run. Performing a visual inspection prior to running the EVAP test may prevent having to repeat the test. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Oxygen Sensor (O2S/HO2S) System. The test may be used to set the I/M System Status to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.
The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Heated Oxygen Sensor (HO2S) Heater System. The test may be used to set the I/M System Status to YES.
The I/M System Status Display on the scan tool provides an indication of whether the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed the I/M System Status will update to YES, indicating a determination was made, even if all of the other tests for that system have not run.