2004 gmc envoy not heating at all - Envoy GMC Cars & Trucks

1. 2004 GMC Envoy Security light car not start - Questions - Fixya

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IS THE ENGINE THERMOSTAC WORKIG OR MISSING? RUDY PEREZ

The relay in your blower motor is stuck on, there is a TSB for this issue. Replace the blower motor resistor and you'll be back in business.
How does the resistor get power if the fuse is pulled?
Replacing the resistor will cure both problems. TSB is a technical service bullitin seen below
Subject:HVAC Blower Motor May Run Continuously After Vehicle is Turned Off (Replace Blower Resistor Relay)Models:2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT2004 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon XLwith Manual Control HVAC (RPO CJ3)Built Prior to August, 2003

I have the same problem except the back of mine works but the bottom doesn't. Passenger side is fine. Let me know what you find out if you could.

More than likely the throttle body needs cleaning

Leave 02 sensor alone ,it is doing it's job . It is heated up because of lean fuel mixture due to incorrect engine temp.,replace thermostat before looking further.

CHECK THE BLACK AND WHITE GROUND WIRE IN CLUSTER.SEE IF ITS COME LOOSE OR BROKE.CAUTION BECAREFUL WORKING ON CLUSTER .BECAUSE OF AIR BAGS DISABLE AIR BAGS WHEN WORKING ON ANYTHING ON STEERING COLUMN AND DASH.

Work for a GM dealership. the problem is the heated seat pad element is bad. Replacing the element is not easy but can be done at home.

locate the heated seat button and the heated seat should start to work

Yes u must de-trim the seat cushion, the element is inside the seat, this is not a job for the novice, get the part yourself and take it to an automotive trim shop.