Reading and Clearing Diagnostic Trouble Codes

The CJ2 air conditioning is equipped with an on-board diagnostic feature which allows the heater-A/C control to detect certain system faults. The diagnostic feature can also be used to display certain data parameters. If the heater-A/C control detects a fault in the system, the man symbol will flash during the first 2 minutes of vehicle operation.

Entry into the diagnostic mode is gained by depressing both temperature knobs at the same time for 5 seconds. There are two display modes within diagnostics, the diagnostic pointer and the diagnostic value. By rotating the driver temperature knob one detent in either direction, the display is toggled between pointer and value. The value displayed is the decimal equivalent of the RAM's contents. A 2 is formed using the minus sign, and the leading 1 in order to display values over 199.

The diagnostic pointer mode is identified by a minus sign preceding the pointer number. The pointer provides an index, identifying the corresponding diagnostic value. The Diagnostic Trouble Codes (DTCs) reside under diagnostic pointer -00. The pointer will be set to this position upon initial entry into diagnostics. If more than one code exists, they will be displayed sequentially at a rate of 2 seconds per fault. Rotating the passenger temperature knob will switch the diagnostic pointers. A wrap around feature is provided if the pointer is continued past either end. Other data used by the computer resides under different diagnostic pointers, and may not be of use in observing the system. To exit the diagnostic mode, press any mode button.




A list of Diagnostic Trouble Codes and their meanings are shown in the illustration.

IMPORTANT: A two digit trouble code indicates the fault is current. A three digit trouble code indicates a history fault.

Clearing Codes
To clear codes from the heater-A/C control press the A/C mode button.