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Discussion Starter · #1 ·
I know this has been an issue on many trucks and suv's but I could never find a solid answer I have a 2005 GMC Yukon Denali both front heated seats wont stay on or work. The light turns on for a second and then click underneath the driver seat and nothing. I just discovered this week now twice while I'm driving both front heaters will work for a couple mins. The adjustable pedal works. Have disconnected it and still the same. Have removed both seats and checked wires and harnesses. Strange thing is while I'm adjusting drivers seat and use the seat heaters it turns on and works. I've has this issue since last year and your help would be appreciated. Thank you
 

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First, ...let's check some fuses.

The fuse is a red 50 amp square fuse in the underhood fuse block labeled MBEC or LBEC. Have a close look at these for being popped.

Get a circuit testor, ...at the back of the seat near the bottom is there large black connector?
The large black has all the seat movement and heater circuits.

There are 2 large terminals and they can become overheated and loose connection. Check those first.

Separate black connector look at all areas of the black connector. The yellow connector is the air bags, leave that alone.
Look VERY CLOSE for discolored terminals at the corners for the large terminals.

If there is some yellow/brownish discoloration on the two side terminals (bigger than the ones in the middle). They are powered by heavy gauge wires that are color coded orange (top) and black (bottom). If the orange wire had about 1/2" of brownish discoloration on it next to the connector replace the metal fitting or replace the connector.

I'm leaving you a schematic as what I think the wiring might be.

Text White Line Font Diagram
 

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Discussion Starter · #3 ·
Thank you so much Motor City Rick. I will check that fuse when I get home today. And wires I will check them this weekend I had checked them before but I will double check the wires for discoloration. The wiring schematic really helps. I'll let you know what I find
 

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If I'm in error, send me good quality photos of the connectors, power boxes etc. so I stay on point (and others) with accuracy. I always have my doubts with schematics because GM "always" has variances in data presented.
 

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Discussion Starter · #5 ·
Motor City Rick, I checked both fuses and both are ok I check the wiring and harness and they are ok and as you described. No yellowing or growing stuff and no melted plastic in or around the terminals, wiring or harness. But on the diagram you provided i think it's for the left rear seat
 

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As of right now, ..I need you to go to your glove box and give me the option code for your seats.
It should be any of these option codes: AG2, ...AN3 w/ULT or wo/ULT. I'm finding too many electrical schematics variations for vehicle.

See if you can find See GM TSB 05-08-143-001 and see if this applies to you???

Next, ...if possible, find a scan tool that can read "Body Codes". All those codes will begin with the letter "B". Record those codes for this session.

Question that needs to be asked: Is the right side door windows affected also on your 2005 GMC Yukon Danali?
If so, chances are the 50A MBEC1 maxi fuse in the under hood fuse box is blown. If not go to next step.

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If the 50A MBEC1 maxi fuse in the under hood fuse box is not blown, check for power on the large orange wire under each seat.
Is there 12 volt battery power present with the ignition off going into the module???

Here's a link that I found that might match your wiring needs. Rotate the schematic clockwise 1 step for better viewing.
http://ww2.justanswer.com/uploads/JHoop/2009-09-28_181254_1.pdf

If you have power going to this module and it is not turning on then chances are that this module is bad. It is the seat control module and is prone to fail on this vehicle. First make sure that the wiring under the seat is in good shape. It is common for the wiring to wear through and cause this. If the wiring is fine then the module is bad.

I will give a brief overview of how your heated seats function before you start poking wires.

Both the driver and passenger seats have 2 heating elements. One is in the seat cushion and the other is in the seat back. The heated seats are capable of obtaining temperatures of 98°F in LOW mode and 107°F in HIGH mode. Battery voltage is supplied to the heated seat module from the SEO2 30A fuse and through a PTC device. The PTC is hardwired in the battery voltage supply circuit in the seat harness assembly and provides extra circuit protection. Ignition voltage is supplied to the heated seat switch from the IGN3 10A fuse. When the heated seat switch is pressed ignition voltage is supplied to the solid state switching device within the heated seat switch assembly. The first time the heated seat switch is activated the solid state switching device supplies voltage to illuminate the high LED indicator and a signal voltage to the heated seat module indicating the high mode is active. The second time the heated seat switch is activated the solid state switching device supplies voltage to illuminate the low LED indicator and a voltage signal to the heated seat module indicating the low mode is active. When the heated seat module receives a high or low mode active signal from the heated seat switch signal circuit, battery voltage is supplied to the seat cushion and back heater elements. The heated seat cushion thermistor provides a signal to the heated seat module used to determine the seat cushion temperature. The heated seat module regulates the supply voltage to the heater elements according to the inputs from the heated seat switch and the seat cushion thermistor.

Here are more schematics that I found not knowing your seat option.

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Text White Font Line Design
Text Diagram Circuit component Passive circuit component Font
Text Diagram Circuit component Passive circuit component Font
 

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Discussion Starter · #10 ·
Hey. I my rpo code is AG2 without ULT. Fuses and window/door functions are ok. I dont have access to a scan tool that reads body codes. Both orange wires underneath both front seats have power going to them. So does the orange wire going to the module under the driver seat. Maybe the module is bad or do u think it needs that software update from the dealership? Thanks for the schematics I'll look at them also
 

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I stated:
"If you have power going to this module and it is not turning on then chances are that this module is bad. It is the seat control module and is prone to fail on this vehicle. First make sure that the wiring under the seat is in good shape. It is common for the wiring to wear through and cause this. If the wiring is fine then the module is bad."

But, before we do this expensive replacement, I need you to use an very good ohmmeter on every black wire of that module. Back probe the black module wire to a known good ground. Resistance should be zero ohms. Anything higher clean ground connection. If infinity, you have a open ground circuit / broken connector or wire.

Next, see if any electrical signals are going out of the memory module when hitting the heater switch. Colors I'm concerned with are the dark blue wires.
 

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Discussion Starter · #12 ·
I hope it's not the module. I'll go out and buy an ohmmeter this weekend to check the resistance of the ground wires. And then check the wires coming out of module. I'm putting this off until the weekend because my water pump messed up, 2nd time in 2 years. Thank you so much for your step by step help. I appreciate it!
 

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Discussion Starter · #14 ·
1st one was just a normal failure, water through the weep hole.. this time bearing failure. Both were AC Delco. New one is ACD as well. It recently started squeaking, so I removed belt and tried pulley by pulley. WP pulley didn't moved smoothly. Then had alot of play in it. Up and down, in and out. I lost my receipt and they couldn't honor the lifetime warranty, so I had to pay for the new one.
 

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What motor / vehicle is it??? Is there a "mechanical fan" attached to this water pump???

Is there over 100,000 miles on the original pump??? How far did you get on the second pump???

Was the anti freeze scuzzie???
 

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Discussion Starter · #16 ·
It's a 2005 gmc Yukon denali with the 6.0L. No, it has the dual electric fans. I'm not the original owner, I'm the 2nd owner. I replaced the 1st pump at around 185K. This one is being replaced at about 197K. The antifreeze is clean, just replaced radiator 1 year ago. Just flushed the rad, motor and heater core (front and back) last month.
 
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