Testing & Diagnosis: Preparation

NOTE: If vehicle is towed in or is suspected of having intermittent problems, DO NOT turn the ignition key off. Diagnostic codes may be stored in the continuous testing memory.

Correct test results for system are dependent on the correct operation of several related non-EEC components and systems. All non-EEC problems should be corrected before attempting to diagnose the EEC system.

Before hooking up any equipment to diagnose the EEC system, make the following checks:

Verify condition of air cleaner and air ducting.
Check all vacuum hoses for leaks, restrictions, and proper routing.
Check the EEC-IV system wiring harness electrical connections for corrosion, loose or detached connectors, loose wires or terminals, and proper routing.
Check the ECA, sensors and actuators for physical damage.
Perform all necessary safety precautions to prevent personal injury or vehicle damage.
Set parking brake and place shift lever in "P" for auto. trans., and Neutral for man. trans. DO NOT move shift lever during testing unless specifically directed to do so.
Turn off all lights and accessories, and make sure that vehicle doors are closed when making readings.
Check and correct coolant level.
Start engine and idle until upper radiator hose is hot and pressurized and throttle is off fast idle. Check for leaks around exhaust manifold, exhaust gas oxygen sensor, and vacuum hose connections.
Turn ignition key off. Service items as required, then go to EQUIPMENT HOOK-UP .