Preliminary Inspection

BASIC KNOWLEDGE AND TOOLS
To use the Powertrain Management section most effectively, a general understanding of basic electrical circuits and circuit testing tools is required. You should be familiar with wiring diagrams, the meaning of voltage, ohms, amps, the basic theories of electricity, and understand what happens in an open or shorted wire.

To perform system diagnosis, the use of a Tech 1 Diagnostic Computer or equivalent scan tool is required. A test light, ohmmeter, digital voltmeter with 10 megohms impedance, vacuum gauge, and jumper wires are also required. Become acquainted with the special tools and their use before attempting to diagnose a vehicle. Special tools which are required for system service are illustrated in Tools and Equipment.

VISUAL / PHYSICAL UNDERHOOD INSPECTION
A careful visual and physical underhood inspection must be performed as art of any diagnostic procedure or in finding the cause of emissions test failure. This can often lead to fixing a problem without further steps. Inspect all vacuum hoses for correct routing, pinches, cuts, or disconnects. Be sure to inspect hoses that are difficult to see beneath the air cleaner, compressor, generator, etc. Inspect all the wires in the engine compartment for proper connections, burned or chafed spots, pinched wires, or contact with sharp edges or hot exhaust manifolds. This visual / physical inspection is very portant. It must be done carefully and thoroughly.

DIAGNOSTIC PREPARATIONS
All of the Diagnostic procedures have specific conditions under which each test is to be performed. Basic conditions that apply to all tests are:

- Battery in good condition and fully charged.
- Adequate fuel in the fuel tank.
- Fuel is uncontaminated.
- Service components in good condition (Fuel Filter, Spark Plugs)

Read each test procedure carefully to determine additional test conditions.


DIAGNOSTIC INFORMATION
The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present.

There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in Computers and Control Systems / System Diagnosis. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications.

MAINTENANCE SCHEDULE
Refer to Maintenance for the maintenance that the owner or technician should perform in order to retain emission control performance.