- 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 INFORMATION
After the visual / physical underhood inspection. The On-Board Diagnostic (OBD) system check is the starting point for all diagnostic procedures and for locating the cause of an emissions test failure.
The correct procedure to diagnose a fault is to follow three basic steps.

1. Are the on-board diagnostics working?
This is determined by performing the On-Board Diagnostic (OBD) system check. This is the starting point for the diagnostic procedures and for finding the cause of an emissions test failure. If the on-board diagnostics are not working, the On-Board Diagnostic (OBD) system check will lead to diagnostic charts in Computers and Control Systems / System Diagnosis. If the on-board diagnostics are working properly, the next step will be:

2. Is there a Diagnostic Trouble Code (DTC) stored?
If a DTC is stored, go directly to the numbered DTC chart in Computers and Control Systems / System Diagnosis. This will determine if the fault is still present. If no DTC is stored, the next step will be:

3. Scan tool serial data transmitted by the control module.
This involves displaying the information available on the serial data stream with a Tech 1 or one of the tools available for that purpose. Information on the meaning of the various displays and examples of normal readings can be found in Computers and Control Systems / System Diagnosis / Scan Tool Diagnosis. Testing and Inspection

TOOLS NEEDED TO SERVICE THE SYSTEM
The system requires a Tech 1, test light, digital multimeter with 10 megohms impedance J 39200, vacuum gage and jumper wires for diagnosis. A test light or voltmeter must be used when specified in the procedures.
For more complete information on the operation of these tools, consult the tool manufacturer's instructions.