02 GMC Denali front heated seats won't work

Sounds like you need a new thermostat. When its cold its sticking.

Rear heat not working ? The blower motor isn't working ? No air coming from the rear vent's ? Is it just a yukon or XL or denali ? What size engine ? 4.8 , 5.3 or 6.0 l Manual or automatic climate control ? Does the blower motor work on any speed ? The front an rear heater system are seperate , have there own electrical circuits . Could have a couple of different systems ,could have a control processor or relay's an a resistor block . Do you know how to test automotive electrical circuit's using a wiring diagram and a DVOM - digital volt ohm meter ? Plus to get at the rear heater-A/C unit you would need to take the right rear trim panel off .
2003 Tahoe No Rear Heat Fix Suburban Yukon XL Repair

the heat element in the seat might be worn out

check the power plug array and see that the terminals are not corroded

checkl fusers and cables to that
the problem is 100% with power

I am having similiar problems with my 06 Denali. Mine does the same thing but also does not blow hot air when in idle.

hello, have someone check all fuses-and plugs for the power seat, they may be a relay for this problem, can call autoparts store and ask about any relays for the heated seats and the power seat, if thats not it you may have to replace, electric motor for seat, sounds like a fuse, the way it all quit working..

Same problem on my 01', what fuse is it?? I can't find any blown fuses in the hood block or the one under the seat.

The controller could be bad but I would probe the related wiring first. From your symptoms it sounds like something can not handle the electrical load. You turn the F/R seat heater on but then you turn on the F/L and the whole system fails. It does sound like the source of the problem will be under the drivers seat. Testing needs to be performed to confirm and identify the source. Both seats share the same fuse and ground. This circuit may have a damaged wire or connector somewhere. Inspect and test as much as you can. Also look underneath the seats for anything. Customers are not aware that personal belongings and trash get pushed underneath the seats and will damage wiring. Also excessively moving the seat forward and back will weaken the harness over time. Please write back and let me know what you need. If it is more diagnostic information or suggestions just let me know. Good Luck

See GM TSB 05-08-143-001, If you have Adjustable pedals, especially if they don't work with the memeory buttons, but function with thier own buttons. Its the Brake Pedal Position Sensor is shorted and mesing up the seat module which controls the heaters too. My 05 Suburban had the same issue