03 Denali HVAC problem

Mouse2 · December 31, 2004

Got a problem with the drivers side temp control on my 03 Denali. The mix door is set to full heat (scan value of 31) and will not move when the temp on the head controller is modulated. The scan tool can see the desired position and actual settings but it isn't moving the door. It sets a error code of B0408 "Temp Control 1 Circuit Malfunction" Can anyone tell me if this is a motor failure issue or a head controller issue? The passenger side and rear zone work as they should...

Thanks

Brian

GMCTech · December 31, 2004

90% of the time the problem with the desired/indicated position codes will be a fault with the servo motor that positions the door.

The only way to check is to remove the connector and see what the values do, make sure you have good ground and power at the servo, and also remove the servo, and see if it moves with no door attached to it, and if the values indicate properly.

My guess is you have a dead motor, and replacement should take care of it. If it still under warranty, let the dealer do it, that way if anything gets broken during removal or reinstallation, it's on thier dime.

Hope this helps.

Mouse2 · December 31, 2004

Thanks for the reply. I will pull the servo motor and see of the door is stuck or not. Is there an index position that I have to be concerned with or is this a one position fits application

Brian

GMCTech · December 31, 2004

It will only install one way. Little notches and bumps on the go-zinta.

Hope this helps.

Mouse2 · January 13, 2005

Just a followup post for anyone that might need this...

The B0408 code doe's indicate an actuator failure. I saved $70 by ordering the part (GMC part # 89018365) from GMPartsDirect.com on the web. You have to wait 10 days to get the part, but it was worth the savings for me. The Drivers side is accessible from the passenger side by removing the lower cover. I'm not sure that you could replace the passenger side actuator which is located on the top side without removing the dash. You may be able to get at it though the glove compartment opening if you had the correct small tools.

Thanks to GMCTech for the information. I appreciated it since this was my maiden voyage tearing into the new truck.