Symptoms Description
Symptoms cover conditions that are not covered DTCs. Certain conditions can cause multiple symptoms. These conditions are listed together under Symptoms Testing. Conditions that may only cause certain symptoms are listed separately under Additional Symptoms Test. Perform the Symptoms Testing before using the Additional Symptoms Tests. Poor Fuel Fill Quality test may be performed separately from the Symptoms Testing and Additional Symptoms Tests procedures.
Circuit/System Description
Ignition voltage is supplied to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by grounding the MIL control circuit.
This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but does not continue to run. This diagnostic directs the service technician to the appropriate system diagnosis. This diagnostic assumes the vehicle system voltage levels are adequate for starter motor operation. Refer to Battery Inspection/Test and Engine Cranks Slowly . The fuel level supply must be adequate, and the fuel quality must be able to sustain the combustion process.
The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an output driver module (ODM). The ODM output control is configured to operate as a low side driver for the powertrain relay. The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.
The control module enables the appropriate fuel injector pulse for each cylinder. The ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect the engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.
When performing the fuel injector balance test, the scan tool is first used to energize the fuel pump relay. The fuel injector tester or the scan tool is then used to pulse each injector for a precise amount of time, allowing a measured amount of the fuel to be injected. This causes a drop in the system fuel pressure that can be recorded and used to compare each injector.
The control module enables the appropriate fuel injector pulse for each cylinder. The ignition voltage is supplied directly to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. A fuel injector coil winding resistance that is too high or too low will affect the engine driveability. A fuel injector control circuit DTC may not set, but a misfire may be apparent. The fuel injector coil windings are affected by temperature. The resistance of the fuel injector coil windings will increase as the temperature of the fuel injector increases.
The CH-47976 is used to test the fuel pump, fuel system leak down, and the fuel injectors. Following the User Guide, CH 47976-11, and the on screen prompts or selections, will indicate the steps required to perform each of the available tests. The tester will perform all of the tests automatically and display results of the test. The results can also be down loaded for storage and printing.
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 2 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 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.
When the ignition is turned ON, the engine control module (ECM) supplies power to the in-tank fuel pump, by energizing the fuel pump relay. The in-tank fuel pump remains ON as long as the engine is cranking or running and the ECM receives crankshaft reference pulses. If there are no reference pulses, the ECM turns the in-tank fuel pump OFF, 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running. The electric fuel pump is incorporated into the modular fuel pump and sender assembly and is located inside the fuel tank. The fuel pump supplies fuel through a fuel filter, also located in the modular fuel pump and sender assembly, through the fuel feed pipes, to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, located in the modular fuel pump and sender assembly, keeps the fuel available to the fuel injectors at a regulated pressure. When the fuel pressure rises above the pressure regulator calibration, the pressure is relieved, with excess fuel exhausted into the modular fuel pump and sender assembly reservoir.
Test Description
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 in nonblended gasoline, or greater than 85 percent with E85 blended gasoline for flexible fuel applications, can cause driveability conditions such as hesitation, lack of power, stalling, or a no start, and may contribute to fuel system corrosion, deterioration of fuel system components, and a restricted fuel filter.
There are 3 dual-tower ignition coils that are part of the ignition control module (ICM). The ICM contains coil driver circuits that command the coils to operate. The ICM has the following circuits
- An ignition voltage circuit
- A ground
- An ignition control (IC) 1 control circuit for the 1-4 ignition coil
- An IC 2 control circuit for the 2-5 ignition coil
- An IC 3 control circuit for the 3-6 ignition coil
- A low reference circuit
The engine control module (ECM) controls each dual-tower ignition coil by transmitting timing pulses on the ignition coil control circuit to the ICM for the proper coil to enable a spark event.
Description
Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the inspection/maintenance (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 Inspection/Maintenance (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 drive cycles for those particular diagnostics. When all I/M monitored diagnostic tests are completed, the I/M System Status indicators are set to YES. Perform the I/M Complete System Set Procedure if any I/M System Status indicators are set to NO.
The purpose of the evaporative emission (EVAP) Service Bay Test is to aid in resetting the EVAP inspection/maintenance (I/M) system status. For this vehicle that is equipped with the engine off natural vacuum (EONV) diagnostic, the Service Bay Test uses the scan tool to initiate the control module's regular sequence of EVAP system DTC tests, but with different enable criteria. By using the Service Bay Test the I/M indicator can be set without the need for multiple cold soaks.
The scan tool displays for the Service Bay Test are based on the events that occur within the following three categories
- The engine running portion of the tests-The vehicle must remain at rest, in Park, or in Neutral, during this portion of the test. This test inspects for large leaks, a leaking purge valve and/or vent system restrictions. The scan tool will display test progress or the reason for an abort or failure.
- Drive cycle-The scan tool will display time and distance needed to warm the fuel.
- Ignition OFF-During this portion of the test, the engine controller will remain active for up to 45 minutes when the ignition is turned OFF to allow control of the EVAP vent valve and run the EONV test. The engine controller inspects for small leaks during this period by monitoring fuel tank pressure or vacuum. If the system is sealed, there will be a pressure or vacuum change. Pressure or vacuum changes that are less than the calibrated values indicate a leak.
When the EVAP diagnostics are initiated by the Service Bay Test, the scan tool will indicate if the enable conditions listed below are not met, or will display a specific reason if the test aborts. When complete, the display will indicate that the tests passed or failed.