Diagnostic Test Procedures

In the process of controlling the various subsystems, the ECM and BCM continually monitor operating conditions for possible malfunctions. By comparing system conditions against standard operating limits certain circuits and component malfunctions can be detected. A three digit numerical code is stored in the computer memory when a problem is detected by this self diagnostic system.

Fig. 21 Operating Service Mode:

After trouble codes have been displayed, the diagnostic service mode can be used to further test the speed control system. To do so, refer to Fig. 21, and proceed as follows:
1. Following the display of trouble codes, the first available system level will be displayed, which is the ECM system.
2. On all models, depress Hi button on the CCP. This will display ``Data,'' the first available test type.
3. Press Lo button on the CCP to display ``Input,'' the test type level for speed control system testing.
4. Depress Hi button on the CCP. This will displayed the first test type. At this point, press Hi button until the correct test type appears as listed below under the applicable model year.
5. To display the previous test, press Lo button. To return to previous test type, press Off.