Entering Self-Diagnostic Mode

On 1989 models, to enter the diagnostic service mode, turn ignition on, then depress Off and Warm pads on the CRT's Climate Control page simultaneously. Hold until a double beep is heard or a page entitled Service Mode is displayed.
On 1990 models, to enter the diagnostic service mode, turn ignition on, then depress Off and Temp Up pads on the Electronic Climate Control Panel (ECCP) simultaneously. Hold until all display segments have been lite.
Operating vehicle in diagnostic service mode for extended time periods without the engine running will cause the battery to run down and possibly relate false diagnostic information. To ensure proper operation do not operate in diagnostic service mode for longer than 1/2 hour.