The valve is located at rear of engine, behind the intake, black/three hoses and vacuum line. I can tell you this, the manual is not going to give you a diagram of the doors. Here is the chart for improper delivery and temp, from GM service info.
1998 Cadillac Catera | Catera (VIN V) Service Manual | HVAC | HVAC Systems - Automatic | Diagnostic Information and Procedures | Document ID: 283631
Air Delivery and Temperature Control Check
Improper Air Delivery Step
Was the Air Delivery System Check performed?
Go to Step 2
Go to Air Delivery System Check
" Install the scan tool.
" Select the actuator tests from the Air Conditioning SPECIAL FUNCTIONS menu.
" Select one actuator test at a time and command the actuator from 0% to 100%.
" Monitor the air flow when commanding the selected actuator (e.G, good air flow should be felt when the floor actuator is commanded to 100% and none when commanded to 0%.)
Does the scan tool display the status ACTIVE when the actuator is commanded?
Go to Step 3
Go to Step 4
Is good air flow felt when the actuator selected is commanded from 100% to 0%?
Go to Step 4
" Check the actuator that failed for mechanical binding. Repair as needed.
" Check the circuit wiring between the heater and A/C control and the actuator. Repair as needed. Refer to the applicable DTC table related to the actuator for assistance.
Actuator replacement procedures would be shown, from that you could remove them and exercise the doors, but that would not condemn a faulty actuator. Try disconnecting both battery cables and shorting them together. What this does is clear memory and faults. My thinking is, if this is a default in response to a fault, it may correct itself. Mind you if it is a hard fault, it won't take long then for the system to default again. Or, try this recalibration procedure.
Re-Calibrating Actuators After Power Loss
After disconnecting the battery or experiencing a complete power loss, synchronize the electronically operated actuators as follows:
" Turn ignition to the RUN position.
" Simultaneously press the AUTO and OFF buttons (located on the heat and A/C control head) for at least five seconds.
" After initiation, the stepper motors will cycle from one stop to the other. You may hear the motors cycling while calibrating.
Tuesday, January 12th, 2010 AT 10:35 AM