A Important Preliminary Checks

IMPORTANT PRELIMINARY CHECKS BEFORE STARTING
Perform the Computers and Control Systems Diagnostic Check before using the symptom tables. Refer to Diagnostic System Check Computers and Control Systems. Verify all of the following are true:
^ The Powertrain Control Module (PCM) and Malfunction Indicator Lamp (MIL) Service Engine Soon are operating correctly.
^ There are no DTCs stored.
^ Ensure the engine is not in a torque reduction mode. The PCM turns certain injectors OFF or reduces the engine timing when the PCM detects an over torque condition or an abusive maneuver. Refer to Powertrain Control Module (PCM) Description for further information.
^ Ensure that the engine coolant temperature is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the PCM turns the fuel OFF to four cylinders at a time in order to keep engine temperatures from reaching damaging levels. The system perceives Engine Coolant Over Temperature as a lack of power, miss, or rough idle. If the vehicle is operating in Engine Coolant Over Temperature-Fuel Disabled Mode, refer to Engine Overheating in Cooling System for diagnosis. Symptom Related Diagnostic Procedures
^ The scan tool data is within the normal operating range, refer to Scan Tool Data List Scan Tool Data, Normal Values and Definitions
^ Verify the customer concern and locate the correct symptom in the table of contents. Check the items indicated under that symptom.

VISUAL/PHYSICAL CHECK
Several of the symptom procedures ask for a careful visual and physical Check. This step is extremely important. It can lead to correcting a problem without further checks and can save valuable time. This check includes:
^ The PCM grounds for being clean, tight, and in the proper location
^ Vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label-Check thoroughly for any type of leak or restriction.
^ The Mass Air Flow (MAF) sensor installation-The arrows on the plastic portion of the sensor must point toward the engine.
^ The air intake ducts for being collapsed or for having damaged areas
^ Air leaks at throttle body mounting area, MAF sensor, and the intake manifold sealing surfaces
^ The ignition wires for cracking, hardness, and carbon tracking
^ The engine harness wiring and terminals for proper connections, pinches or cuts