A Important Preliminary Checks

Perform Diagnostic System Check - Computers and Control Systems before using the symptom tables, and 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 Diagnostic Trouble Codes (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.
^ 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.