Initial Inspection

CHECKING THE BASICS
All troubleshooting must begin by "Checking the Basics". Certain basic faults are undetectable by the self-diagnostic systems of the fuel and ignition control units, and in some cases can actually interfere with self-checking and fault memory operation.

System fault codes are cleared whenever control unit or battery are disconnected. Therefore, all fault codes should be read prior to any vehicle power interruption or troubleshooting.

Prior to any teardown, repair or component replacement, the following steps should always be considered.

Battery State of Charge
Batteries in a state of partial discharge can have a dramatic effect on control units and related components.

Positive Battery Cable Integrity
All B+ connections must be in perfect condition for trouble-free electronic system operation. Refer to Diagrams for B+ interconnects.

Fuse Integrity
Fuses are employed to prevent possible damage to electrical components and wiring harnesses. Fuses and their connections must be without dynamic resistance. Dynamic resistance can only be checked using the voltage drop method of testing.

Negative Ground Connections
As all electrical circuits are a circle, all B- connections must also be checked and verified to be in perfect condition. A poor "common" ground point will cause seemingly unrelated systems to influence one another. High current systems which encounter a poor "common" ground can back feed through other electrical systems, causing unusual operation and perhaps inexplicable component failure. As with the B+ side of the electrical system, the ground side should be checked dynamically using the voltage drop technique.

Power Train Cable Attachments
Metal cables attached to the engine or transmission which appear overheated and/or discolored indicate the need to thoroughly test all ground connections.

Power Supply Relays
The system relay, as well as its plug connection, can be a source of intermittent operation which will not set a fault code.

Crankshaft Position/Speed Sensor
Monolithic sensors should be checked statically and dynamically. Physical mounting and condition of the sensor must be assured.

High Tension Coil and Secondary Components Wiring
The secondary ignition system should be checked visibly as well as with a suitable engine analyzer and scope. All components should be examined for tight connections and freedom from carbon tracking, moisture and corrosion.

Fuel Delivery
Fuel delivery must begin at once when cranking. Fuel pressure must be within specifications.

Spark Plugs
If out of specification, spark plugs can significantly impair engine performance. Spark plug type, condition and gap must verified according to specification.

Air/Fuel Ratio
When troubleshooting idle quality or driveability complaints, it is necessary to consider the following:
^ Presence of unmetered air leaks
^ Evaporative purge system
^ Excessive engine oil dilution
^ Substandard fuel or unapproved additives
^ Carbon build-up