System Diagnosis and Testing

A Diagnostic Readout Box (DRB) scan tool is necessary for many of the diagnostic procedures. The tool must be connected to the engine diagnostic connector to read any stored diagnostic trouble codes. When the malfunction has been corrected or is no longer detected, the diagnostic trouble code will be erased after 50 ignition key On/Off cycles. However, diagnostic trouble codes will also be erased if the vehicle's battery is disconnected longer than one minute.

Before starting test procedures, visually inspect speed control system for disconnected vacuum hoses, corroded electrical connectors and improper cable operation. After visual inspection, perform the test procedures using the following guidelines:

1. Always start at first diagnostic test. Starting at any other test may give incorrect results.
2. At the end of each test, reconnect all wires and hoses.
3. Ensure vehicle being tested has a fully charged battery.
4. When checking voltage or continuity at the engine controller 60-way connector, use the terminal side (not wire side) of the connector. Use caution when performing electrical tests to prevent accidental shorting of terminals; shorts can damage fuses or engine controller.
5. Perform the indicated verification test after vehicle repairs have been made.