Temperature Gauge not working, AFM inoperable, radiator fan stuck on h

ImminentFailure · March 28, 2016

My 2016 5.3L Sierra (SLE) 4x4 has had been experiencing the issues in the thread title. $2,800 miles on her, two months since delivery as of 3/26/16. Temperature gauge will not rise, radiator fans stuck in high mode, and AFM will not enable V4 mode. I take the same route to work daily and know all the stops V4 runs. I have one 10 mile stretch of totally flat highway.

It happened three times this past week, each time was on the initial drive of the day. During stop and go traffic the second time I shut off and restarted the truck which didn't do anything. When I arrived to work shutting of the truck, waiting 5 minutes and the restarting had no effect. Dealer was unable to pull a code or reproduce last week. No check engine light or other indicators.

Yesterday I was running errands and it occurred and lucky for me I was visiting my parents and my home town GMC dealer is open 10-3 so I wung it in and left it running. Service guy comes out and says 'Hello, what seems to be going on aside from this thing making a ton of noise'. I chuckled. I bet not many of you have heard the radiator fans stuck in 'Coolant Hot / overheat mode'. YOu can hear it in the cab, clear as day with the radio on. In the service area it was absolutely deafening. We had to step outside and shut the doors to talk to each other while his scan tool ran. The only comparison I had it to those car wash blowers that dry your car at the end, right when you are under them.

I did a search and manually browsed 10 pages of topics, didn't seen this one. I'll report back what the dealer finds if anything, and continued troubleshooting or resolution. In the event someone else has this issue they may find value in the information.

pm26 · March 28, 2016

This could be nothing more than a defective temperature sender sending wrong voltage to the ECU. It is apparently still within the operational range so no trouble code is stored. The ECU thinks the truck is running hotter than normal so the radiator fans are on high all the time and it will not enable the V4 mode. I would replace the temperature sender on my own if the dealership does not do it. This is most likely a simple problem with multiple symptoms.

silveradosid · March 28, 2016

heck air intake clamps, my truck did this when i had the air box out. forgot to tighten a clamp properly

ic3man5 · March 29, 2016

Is there coolant in the radiator? No coolant means the sensor won't work.

pm26 · March 29, 2016

Is there coolant in the radiator? No coolant means the sensor won't work.

No coolant would cause the sensor to indicate overheating condition quickly and the check engine light would come on. if the sensor probe is exposed to hot air instead of coolant, it will register extreme overheating quickly as that air will be a lot hotter than hot coolant.

ic3man5 · March 29, 2016

No coolant would cause the sensor to indicate overheating condition quickly and the check engine light would come on. if the sensor probe is exposed to hot air instead of coolant, it will register extreme overheating quickly as that air will be a lot hotter than hot coolant.

Not in any vehicle I've ever owned (and I've had my share fair of radiator leaks) unless GM has some magical way of transferring heat outside convection. No liquid = no heat transfer = no sensor reading. Of course there is still some convection happening with air but its extremely slow compared to coolant/liquid; Your engine will be toast by the time the sensor reads an overheat condition without any coolant.

Checking the coolant level only takes two seconds anyways, A good mechanic will always check that first after looking at the ground for leaks. Trying to pull codes without a check engine light is the symptom of a lazy mechanic/dealership. (Assuming they didn't check anything else). (Oh no code? Working as intended - can't find anything wrong).

1.) Look for leaks / ask owner if they noticed any leaks and or no heat from the vents.

2.) Check for low/no coolant condition.

3.) Check output of sensor directly at the source with a multi-meter (Scan tool might be able to do this also - not a cheap OBD II scanner though).

4.) Scratch your head and look for air bubbles in coolant system and or gauge cluster not working correctly.

muddkatt · March 29, 2016

Not in any vehicle I've ever owned (and I've had my share fair of radiator leaks) unless GM has some magical way of transferring heat outside convection. No liquid = no heat transfer = no sensor reading. Of course there is still some convection happening with air but its extremely slow compared to coolant/liquid; Your engine will be toast by the time the sensor reads an overheat condition without any coolant.

X2

Been there and done that. Cooked an engine that showed to be running cool. It had NO water/coolant in it.

ImminentFailure · March 29, 2016

The sensor was bad as well as loose and was leakin a considerable amount of collent which I didn't think to check. When I picked it up he said 'we replaced the sensor and she needed coolant badly.'

There was a code stored, P0118 - http://www.obd-codes.com/p0118- Repair order said they tested the connection to PCM and it validation, replaced sensor and reset code.

The powertrain control module (PCM) provides a 5 volt reference and a ground to the sensor. The PCM monitors voltage drop to determine coolant temperature. If the ECT reads less than freezing temp. when engine has been running for more than a few minutes, the PCM determines a circuit fault and sets this code. Or if the PCM determines the sensor resistance is out of specs, this code is set.

DoyleR · November 2, 2019

I just replaced the coolant temp sensor on my 2014 Silverado and the engine fan is still running wide open and the temp gauge is still not working. My mechanic will likely have to figure this one out.

TJay74 · November 4, 2019

On 11/2/2019 at 1:45 PM, DoyleR said:

I just replaced the coolant temp sensor on my 2014 Silverado and the engine fan is still running wide open and the temp gauge is still not working. My mechanic will likely have to figure this one out.

You need to pull the code. The code P0128 and P0118 are both related to the termostat it being stuck open or closed. You need to find out which code you have, the code doesnt always trip the check engine light and instead will just kill the coolant temp gauge instead.

If you are running a lower than the stock OEM 194° thermostat it can cause this code to trip. The ECM has to see at least 167° within so many drive cycles otherwise it will assume the thermostat is stuck open. Issue could be bad coolant temp sensor or bad thermostat or bad wiring.

DoyleR · November 5, 2019

I already changed the coolant temp sensor but that didn't fix the problem. I'll check everything else you mentioned. Thanks for the input

frums143 · November 5, 2019

14 hours ago, DoyleR said:

I already changed the coolant temp sensor but that didn't fix the problem. I'll check everything else you mentioned. Thanks for the input

Try unplugging battery for a bit . It should reset it and temp will work . Happened to me last week . Posted a topic but no one seemed to be able to answer so searched on google

i also had the fans blowing at full speed. changed out thermostat and temp sensor. dealer in phoenix didn't have them so installed autozone one's....well truck didn't like those. bought from dealer and now back to normal.

Edited November 5, 2019 by frums143

TJay74 · November 5, 2019

4 hours ago, frums143 said:

Try unplugging battery for a bit . It should reset it and temp will work . Happened to me last week . Posted a topic but no one seemed to be able to answer so searched on google

i also had the fans blowing at full speed. changed out thermostat and temp sensor. dealer in phoenix didn't have them so installed autozone one's....well truck didn't like those. bought from dealer and now back to normal.

While this will fix the non-operational gauge it wont correct the underlying issue. If that issue isnt found and fixed after about 5 drive cycles the ECM will kill the gauge cluster again and go into fail safe mode.

frums143 · November 6, 2019

22 hours ago, TJay74 said:

While this will fix the non-operational gauge it wont correct the underlying issue. If that issue isnt found and fixed after about 5 drive cycles the ECM will kill the gauge cluster again and go into fail safe mode.

yes very true, forgot to mention that i also changed out my thermostat at same time. installed cheap one from autozone....truck didn't like them lol went to dealer and got oem ones ....back to normal .

Joey Whittaker · December 17, 2019

On 11/2/2019 at 1:45 PM, DoyleR said:

I just replaced the coolant temp sensor on my 2014 Silverado and the engine fan is still running wide open and the temp gauge is still not working. My mechanic will likely have to figure this one out.

my 14 Silverado is doing the same thing!!! Did you find out anything