This 2003 GMC Envoy came in with the complaint that the a/c will only blow out the defrost and floor. Not through the dash vents. I checked codes and found a code B0263 for a fault with the mode actuator. I first ran into this problem after changing a battery in one of these vehicles last year. Whenever the battery is disconnected the HVAC unit will perform a recalibration of all doors. This causes the door motors to be moved full cycle and the mode door will stick some times. I now hook a jump box to the system before changing the battery in Trailblazers or Envoys to prevent a recalibration from occurring. This way I will not be blamed for a stuck actuator motor.
Anyways to change the actuator motor, first drop the hush panel under the driver’s side of the dash. There are some parts that have to be disconnected from the panel including the turn signal flasher assembly shown in the next picture.
Next, I removed the lower dash knee panel to have a little more room to work.
I had to pull a push pin retainer out at the left side of the duct work in order to remove the driver’s floor vent.
Now, I could finally see the actuator on the side of the heater a/c box.
I removed the actuator and installed the new one. Performed a recalibration with my Tech 2 and put all the panels back in place. A recalibration can be done by disconnecting the battery for at least one minute, reconnect the battery, start the engine and leave the a/c controls alone. I would recommend letting the engine run for at least two minutes, turn the ignition off for at least ten seconds but no more than thirty seconds and then restart the engine so that confirmation of the repair can be done.
I do not recommend connecting the wiring to the actuator until it is installed. They come prepositioned for easier installation.
The notch at the lower edge of the gear is an alignment point. There is a corresponding tab on the door linkage that needs to be lined up with this notch.
To purchase the mode valve actuator, please click here. To see updated information about actuator positions and alignment, please click here.
Just clean the throttle plate and throttle bore. Use throttle body cleaner on a rag and wipe the surfaces clean. Do Not Spray throttle body cleaner into the throttle body. It will be a $500 mistake. Use gloves to protect your hands.
Okay so how do I reset the memory? Will just cleaning the throttle body help that or is there a reset type program I need to go through?
If the mode actuator has not been changed yet, there is likely to be an internal gear broken. You should be able to put your hand on the actuator and “feel” to see if it the cause of the noise. The idle issue only has to do with the loss of learned memory for the throttle plate position. Not the size or type of battery.
I haven’t ever changed the actuator unless someone else has in the past. It was 2 years old when I purchased the vehicle. Its been fine until my truck wouldn’t crank on wednesday morning with a dead battery. So who knows. I wondered if Autozone didn’t give me a big enough battery, due to the truck trying to die when the compressor kicks on.
The grinding noise I would suspect is from and improperly installed actuator. The stalling problem is from a loss of computer memory. The throttle plate will need to be cleaned using a rag and throttle body cleaner. Do Not Spray cleaner into the throttle body or you will wind up replacing it.