Displaying and Reading Trouble Codes

Fig. 21 Operating Service Mode:

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.
To enter diagnostic service mode, turn ignition on, then depress Off and Warm buttons on the climate control panel (CCP). Hold buttons until all display panel segments illuminate, indicating the beginning of diagnostic readout. The two display panels must be illuminated, except for turn signal lights, to ensure all segments are operating. Do not attempt diagnosis unless all segments appear, as an improper diagnosis may result. If any segments are inoperative, the display panel must be replaced.