What did you do to your NNBS GMT900 Tahoe/Yukon Today?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Runfor5

Member
Joined
Jan 29, 2022
Posts
73
Reaction score
200
Location
Northern VA
No parts here this group probably isn't familiar with, but some pics for the hell of it. The new water pump (ACDelco) + thermostat housing (GM), the two Dorman heater hose lines connected to the two new Dorman plastic T-fittings at firewall, Denso radiator w those new GM oil cooler lines in, and some ACDelco rad hoses. I'm annoyed I didn't buy new the 2 coolant hoses that go to the top of the coolant reservoir tank + going from top of engine block to radiator, since I touched everything else lol. At least those are easy if I order eventually.

Will take a break on this car for a bit (hopefully). Perhaps various suspension components will be the next 'preventative' thing to get ahead on for me.

IMG_9425.jpg

IMG_9428.jpg

IMG_9439.jpg
 

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
6,299
Reaction score
15,534
Location
Richmond, VA
No parts here this group probably isn't familiar with, but some pics for the hell of it. The new water pump (ACDelco) + thermostat housing (GM), the two Dorman heater hose lines connected to the two new Dorman plastic T-fittings at firewall, Denso radiator w those new GM oil cooler lines in, and some ACDelco rad hoses. I'm annoyed I didn't buy new the 2 coolant hoses that go to the top of the coolant reservoir tank + going from top of engine block to radiator, since I touched everything else lol. At least those are easy if I order eventually.

Will take a break on this car for a bit (hopefully). Perhaps various suspension components will be the next 'preventative' thing to get ahead on for me.

View attachment 431562

View attachment 431563

View attachment 431564
I love me some forward-thinking preventative maintenance! Well done. I was kicking myself this weekend for not replacing the suspension compressor 2 years ago when I did the rear shocks.
 

j91z28d1

Full Access Member
Joined
Feb 28, 2022
Posts
2,957
Reaction score
3,595
The outside temp sensor is in front of radiator on a little bracket more on the passenger side I believe..

Looks like it can be either driver or passenger side depending on options.
View attachment 431301


so this morning I got curious why none of the 3 Temps match up.

so I disconnected this sensor with the truck running and the scanner intake and ambient Temps pulled up... nothing happened. went inside and the hvac said the default, 58deg or so. no check engine light or anything. so I reconnected, did the 2 buttons at once to update the temp and it showed 93deg, but still didn't match either temp on the scanner, it said ambience was 100 something and intake 120 ish.

so I have no idea where it's getting these Temps from haha. it's always been common for the intake temp sensor to be in the maf. but now I'm not sure, need to do more digging.
 

Doubeleive

Wes
Supporting Member
Joined
Nov 7, 2017
Posts
25,663
Reaction score
38,217
Location
Stockton, Ca.
put maybe 20 miles on it since changing the plugs, left bank (bank 1) has had some light intermittent noise in the past but now has some rotational noise at around 1100rpm, can't hear it idle and it goes away at higher rpm, so didn't feel confident driving it like that, dropped it off at the dealer yesterday and they confirmed the same noise so the left head is going to get pulled and if I am lucky I will just get away with doing the left bank. They will update me once the cam has been inspected.
wierd because it runs smooth as silk otherwise.

and if anyone has been waiting for the dealer computers to be back up and running they are fixed as of this morning, I guess the software company forked over 40 mill to get there system back.
 
Joined
Apr 11, 2018
Posts
7,124
Reaction score
14,356
Location
St. Louis
so this morning I got curious why none of the 3 Temps match up.

so I disconnected this sensor with the truck running and the scanner intake and ambient Temps pulled up... nothing happened. went inside and the hvac said the default, 58deg or so. no check engine light or anything. so I reconnected, did the 2 buttons at once to update the temp and it showed 93deg, but still didn't match either temp on the scanner, it said ambience was 100 something and intake 120 ish.

so I have no idea where it's getting these Temps from haha. it's always been common for the intake temp sensor to be in the maf. but now I'm not sure, need to do more digging.
I've had this info in a file for about 5 years. Not sure where I got it, might've been posted on this board at one time, but it describes the outside air temp behavior.

The outside air temperature is displayed on the Driver Information Center (Fig. 8), radio or rear view mirror in a number of GM vehicles. There may be some confusion about the operation of the display and how quickly it updates ambient temperature. Depending on several factors, the temperature may not be updated immediately and owners may feel that the display is inaccurate at times.

The ambient air temperature sensor is a variable resistor interfaced to the Body Control Module (BCM). The BCM provides the logic for reading the ambient air temperature sensor, filtering the data and transmitting the information via the serial data circuit to the outside temperature display. The outside air temperature algorithm uses three pieces of information: outside air temperature data, vehicle speed, and the time the engine was turned off.

When the engine is first started, the algorithm looks at how long the engine was off and if the outside temperature is lower than the last reading taken during the previous ignition cycle. From this information, it's determined if a new outside temperature reading should be taken.

If the engine was off long enough or the current outside air temperature is cooler than the stored value, a new outside temperature reading is taken and displayed. If the engine was not off long enough or the current outside air temperature is higher than the stored value from the previous ignition cycle, the last stored value of outside air temperature taken will be displayed.

The outside air temperature will continue to be updated every second as long as the outside air temperature is the same or cooler than the previous reading. Once the new outside air temperature reading exceeds the previous temperature and the vehicle is traveling less than 18 mph (29 km/h), the displayed outside air temperature will remain at its last value. Once the vehicle speed exceeds 18 mph, the displayed outside air temperature will be updated. If the speed drops below 18 mph, the outside air temperature will freeze at its last value.

The ambient temperature display (Fig. 12) may be slow to update the outside temperature at times or the A/C compressor may not operate due to low ambient temperature on some 2008-2012 Enclave; 2009-2012 Traverse; 2007-2010 OUTLOOK; 2007-2012 Acadia, Escalade, Escalade ESV, Escalade EXT, Avalanche, Silverado, Suburban, Tahoe, Sierra, Yukon, Yukon Denali, Yukon XL, and Yukon Denali XL models.

The outside air temperature display utilizes a very specific filtering routine of the Ambient Temperature Sensor signal so the display will update gradually without making large jumps in the reading. This is designed to eliminate the possibility of erratic readings under certain driving conditions.

The temperature display is always allowed to update quickly when the ambient temperature is getting colder while driving, but the display takes much longer to update when the temperature is getting warmer. This prevents false updates to the temperature display while driving in slow or stop-and-go traffic in hot weather.

The temperature display will always read the actual ambient temperature when the vehicle is started if the temperature has dropped since the last key cycle. It will not immediately update to the actual ambient temperature if it has gotten warmer since the last key cycle unless the ignition has been off for at least 2.5 hours.
 

j91z28d1

Full Access Member
Joined
Feb 28, 2022
Posts
2,957
Reaction score
3,595
I've had this info in a file for about 5 years. Not sure where I got it, might've been posted on this board at one time, but it describes the outside air temp behavior.

The outside air temperature is displayed on the Driver Information Center (Fig. 8), radio or rear view mirror in a number of GM vehicles. There may be some confusion about the operation of the display and how quickly it updates ambient temperature. Depending on several factors, the temperature may not be updated immediately and owners may feel that the display is inaccurate at times.

The ambient air temperature sensor is a variable resistor interfaced to the Body Control Module (BCM). The BCM provides the logic for reading the ambient air temperature sensor, filtering the data and transmitting the information via the serial data circuit to the outside temperature display. The outside air temperature algorithm uses three pieces of information: outside air temperature data, vehicle speed, and the time the engine was turned off.

When the engine is first started, the algorithm looks at how long the engine was off and if the outside temperature is lower than the last reading taken during the previous ignition cycle. From this information, it's determined if a new outside temperature reading should be taken.

If the engine was off long enough or the current outside air temperature is cooler than the stored value, a new outside temperature reading is taken and displayed. If the engine was not off long enough or the current outside air temperature is higher than the stored value from the previous ignition cycle, the last stored value of outside air temperature taken will be displayed.

The outside air temperature will continue to be updated every second as long as the outside air temperature is the same or cooler than the previous reading. Once the new outside air temperature reading exceeds the previous temperature and the vehicle is traveling less than 18 mph (29 km/h), the displayed outside air temperature will remain at its last value. Once the vehicle speed exceeds 18 mph, the displayed outside air temperature will be updated. If the speed drops below 18 mph, the outside air temperature will freeze at its last value.

The ambient temperature display (Fig. 12) may be slow to update the outside temperature at times or the A/C compressor may not operate due to low ambient temperature on some 2008-2012 Enclave; 2009-2012 Traverse; 2007-2010 OUTLOOK; 2007-2012 Acadia, Escalade, Escalade ESV, Escalade EXT, Avalanche, Silverado, Suburban, Tahoe, Sierra, Yukon, Yukon Denali, Yukon XL, and Yukon Denali XL models.

The outside air temperature display utilizes a very specific filtering routine of the Ambient Temperature Sensor signal so the display will update gradually without making large jumps in the reading. This is designed to eliminate the possibility of erratic readings under certain driving conditions.

The temperature display is always allowed to update quickly when the ambient temperature is getting colder while driving, but the display takes much longer to update when the temperature is getting warmer. This prevents false updates to the temperature display while driving in slow or stop-and-go traffic in hot weather.

The temperature display will always read the actual ambient temperature when the vehicle is started if the temperature has dropped since the last key cycle. It will not immediately update to the actual ambient temperature if it has gotten warmer since the last key cycle unless the ignition has been off for at least 2.5 hours.


yeah that sounds right. basically trying to filter out heat soak for hvac use and driver display. you can skip all that and make it update by hitting the ac button and recirculate button at the same time.

I found something similar with my other car when that temp outside sensor started going out, but you gotta hit 3 buttons at once for an update.



what gets me is I have 2 temp readings on my scanner. intake air temp and ambient air temp and both read differently, both keep working with that physical outside sensor unplugged.

back in the day(90s gm) intake air temp was basically manifold air temp, they had a sensor in the plenum itself. sometimes a big brass coolent temp sensor that was slow to change, so you'd get aluminum manifold temp itself, others were the same size but had the little ball and plastic cage and would read the air temp just before it split off to the ports. different ecm codes used the data in different ways. especially during heat soak hot restart cranking fuel maps.

I thought all intake Temps had moved to the maf these days. seems like there's something else going on here.

the scanner ambient air temp is much more stable than scanner intake temp. it never matches the actual outside air temp reading thou, even with a forced update. could be some crazy math off the maf temp sensor, but still has me curious.


when I get time I am thinking I'll unpin the maf temp sensor to see if it effects both readings.
 

j91z28d1

Full Access Member
Joined
Feb 28, 2022
Posts
2,957
Reaction score
3,595
I'm completely confused by these Temps sensors..

so today I checked the diagram, yep only intake air sensor wiring is in the maf. so I go pull up the scanner, start the truck and watch the intake temp and the ambient air temp. they are different by about 20deg.

unplug the maf, the intake air temp goes to its default of negative whatever, the ambient temp doesn't move, then I plug it back in and intake temp goes back to 120ish, all of a sudden the ambient temp goes to 14deg F and both cooling fan kick on max. like wtf? I didn't touch the sensor in the bumper.

so check codes and ambient air temp open code, very weird. havc still says 98deg. yesterday when I unplugged then air sensor in the bumper the hvac detailed to 58deg. I force update that by hitting the 2 buttons, it jumps to 100deg. scanner still reading 14, fans still on max.


so I pull out the tech 2, check everything, havc module still reading ambient Air raw same as havc display (ish 2deg off). go into ecm data and intake temp normal, ambient 14F. clear codes a few times, cycle power. still the same, so I take it for a drive thinking it needs to reset at a speed. take it up to 60mph and still 14, weird.

drive it back to the shop, pull in, turn the ac off and the cooling fans go off high speed, pick up the scanner. now the ambient Air temp is 17F.


i got nothing. parked it, went inside for a bit, checked it later and it's at 18deg F. fans not on, no codes for anything. my only guess is it will reset itself slowly over time. it's gotta be a fake temp like oil temp, somehow using maf temp and math to guess for something filtered.


not that any of this matters to anyone else haha, but if you want to compare the outside air temp to your intake air temp as it passes thru the maf, you'd have to force update the hvac display temp and look at the manifold air temp to see how well your cold air box is working. mines about 20deg different cruising, creeps up to more like 30deg at stopped in traffic.


and if you ever get a ambient Air temp sensor fault code, but the hvac temp is correct. I have no clue how to fix that haha. maybe an intermittent wire in your maf sensor plug.
 

Forum statistics

Threads
131,698
Posts
1,855,395
Members
95,934
Latest member
jdt212

Latest posts

Top