OBD II Readout on climate control panel

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------------------------------------------------ On-Board Diagnosis Mode

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 may 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 pressing in on both temperature knobs at the same time for 5 seconds. The following display modes are found within diagnostics:

• The diagnostic pointer * The diagnostic value

Important

A 2-digit trouble code indicates the fault is current. A 3-digit trouble code indicates a history fault.

By rotating the driver temperature knob one position in either direction, the display is toggled between pointer and value. The value displayed is the decimal equivalent of the RAM contents. A 2 is formed using the minus sign and the leading 1 in order to display values over

A diagnostic pointer mode is identified by a minus sign preceding the pointer number. The pointer provides an index, which identifies 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, the codes 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. Press any mode button in order to exit the diagnostic mode.

Thanks to Bon'ne'ville for the requested instructions on accessing OBD via the climate control system.

The only code that was displayed was a history code (105).

I assume the a/c on this vehicle is controlled by a computer or controller that takes sun load, inside temp, and exterior temp into account when deciding to what position the blend doors should be commanded. However, it would seem to me that in the single (driver) control mode whatever position the belnd doors were commanded to would be the same and therefore the air exiting the vents would all be very similiar.

Since both the driver-side blend door motor and the exterior temp sensor have been replaced, I am at a loss as to where else to look unless there is a problem with the a/c & heater controller unit causing the problem. If the controller was defective, I would expect to get an OBD code but none are present.

I would appreciate any suggestions you might have on isolating/resolving this problem.

Ray

I have not looked into the "technical" aspects of this system... but it seems like there would have to be two interior temp sensors? I would "guess" that even in the single (driver) control mode... the system would attempt to get both interior temp sensors to read whatever temp the driver control is set for. In other words, if you're driving west and the sun is beating in on the driver side... it would apply more cold air to the driver side and less to the passenger side; so that both sides maintained the proper temp? So, a bad interior temp sensor on the passenger side would still screw up the blend command when you were in single (driver) control mode?

"Ray" wrote in message news:1JWdnRX5Msb7cV_anZ2dnUVZ snipped-for-privacy@comcast.com...

David:

It is my understanding the system only has one interior sensor. However, without a schematic of the system I am not sure if that is true nor am I sure of just what inputs control the position of the blend doors. Hopefully someone with access to the schematic for this system will respond with some helpful suggestions.

Ray

I would be interested to know, too. Mine works... but I don't really know how it works! LOL