Ambient air temp issues?

RyanS · January 7, 2020

New to this so seeing how this works. It’s a long story, this is the shortest version of my nightmare with this truck.

I bought my 2015 GMC Sierra 2500hd Denali with duramax in July 2019. The second I drove off the lot, check engine light came on. They replaced my air intake damper (I think that’s what it’s called, I’m just a carpenter so bare with me). Drove it off the lot again after that fix, came right back on. That time it was “low voltage to my ECM” so they replaced my ECM, cut the engine harness and spliced some wires. It turned the check engine light off but no readings for the exterior temp inside the truck once this was done. It worked perfectly fine before this fix. Brought it right back and this time they said my instrument cluster was shot. It took 3 weeks to get it fixed, and my temp gauge is reading -38 outside. They gave me the truck back and said give it a day to reset the temp sensor. Still reading -38 degrees outside and it’s about 35 out currently. Looking for some direction or to see if anyone has had issues like this.

thanks,

ryan

JimCost2014 · January 7, 2020

27 minutes ago, RyanS said:

New to this so seeing how this works. It’s a long story, this is the shortest version of my nightmare with this truck.

I bought my 2015 GMC Sierra 2500hd Denali with duramax in July 2019. The second I drove off the lot, check engine light came on. They replaced my air intake damper (I think that’s what it’s called, I’m just a carpenter so bare with me). Drove it off the lot again after that fix, came right back on. That time it was “low voltage to my ECM” so they replaced my ECM, cut the engine harness and spliced some wires. It turned the check engine light off but no readings for the exterior temp inside the truck once this was done. It worked perfectly fine before this fix. Brought it right back and this time they said my instrument cluster was shot. It took 3 weeks to get it fixed, and my temp gauge is reading -38 outside. They gave me the truck back and said give it a day to reset the temp sensor. Still reading -38 degrees outside and it’s about 35 out currently. Looking for some direction or to see if anyone has had issues like this.

thanks,

ryan

Welcome to the site.

Did they say why the factory wiring harness was, or needed to be cut?

Do you have the work order with an explanation? Seems like whatever they did caused the problem.

RyanS · January 7, 2020

They did not fully explain to me. I will take photos of work orders so you can see. they didn’t make a record that they cut the harness but wire splices made to the air temp sensor in grill made it obvious and as well as new uncased wires that weren’t there before made me ask questions. They told me it was a “Gm certified repair”. Looking further into it myself, I did find that there are some wires added running to trailer lights fuse, which raises the question of my mirrors are factor or after market. Reading into it I’m nervous I’m missing a sensor that may be causing the issues? I will post what was done to it in pics

7 minutes ago, JimCost2014 said:

Welcome to the site.

Did they say why the factory wiring harness was, or needed to be cut?

Do you have the work order with an explanation? Seems like whatever they did caused the problem.

BlancoSilverado · January 7, 2020

IMO, I would probably return the truck and cut your losses. It might cost you a few $$ but might save you more in the long run.

JimCost2014 · January 7, 2020

3 minutes ago, RyanS said:

They did not fully explain to me. I will take photos of work orders so you can see. they didn’t make a record that they cut the harness but wire splices made to the air temp sensor in grill made it obvious and as well as new uncased wires that weren’t there before made me ask questions. They told me it was a “Gm certified repair”. Looking further into it myself, I did find that there are some wires added running to trailer lights fuse, which raises the question of my mirrors are factor or after market. Reading into it I’m nervous I’m missing a sensor that may be causing the issues? I will post what was done to it in pics

Believe the sensor is in the passenger mirror housing, at the bottom of it, by the puddle light.

RyanS · January 7, 2020

3 minutes ago, JimCost2014 said:

Believe the sensor is in the passenger mirror housing, at the bottom of it, by the puddle light.

The passages side tow mirror has no sensor. I’d take a pic but I don’t know how to send on the forum.

JimCost2014 · January 7, 2020

1 hour ago, RyanS said:

The passages side tow mirror has no sensor. I’d take a pic but I don’t know how to send on the forum.

On to plan B:

Outside Air Temperature (2500/3500 series)

The Ambient Air Temperature Sensor is located behind the grille and varies it’s resistance with temperature. The Instrument Cluster reads the resistance value to determine temperature. The time of and rate of the temperature update is based on an algorithm in the Instrument Cluster software.

Factors such as, last reading, current reading, length of time vehicle is been off/on, power mode, vehicle speed, driven distance, and sensor location are all considered by the Instrument Cluster to know when to update the displayed temperature on the Info Display Module. For example, if the sensor is located near the engine compartment, and the vehicle has been turned off for only 10 minutes then restarted, the Instrument Cluster will wait until the vehicle is driven to get more accurate air flow across the sensor before it updates the display.

On vehicles with diesel engines and RPO AVF, there is an additional Ambient Air Temperature Sensor in the Passenger Outside Rearview Mirror. The Engine Control Module (ECM) reads the resistance value of this sensor to determine outside temperature. This temperature reading is only used for powertrain purposes and is not used for the displayed temperature on the Info Display Module.

RyanS · January 8, 2020

52 minutes ago, JimCost2014 said:

On to plan B:

Outside Air Temperature (2500/3500 series)

The Ambient Air Temperature Sensor is located behind the grille and varies it’s resistance with temperature. The Instrument Cluster reads the resistance value to determine temperature. The time of and rate of the temperature update is based on an algorithm in the Instrument Cluster software.

Factors such as, last reading, current reading, length of time vehicle is been off/on, power mode, vehicle speed, driven distance, and sensor location are all considered by the Instrument Cluster to know when to update the displayed temperature on the Info Display Module. For example, if the sensor is located near the engine compartment, and the vehicle has been turned off for only 10 minutes then restarted, the Instrument Cluster will wait until the vehicle is driven to get more accurate air flow across the sensor before it updates the display.

On vehicles with diesel engines and RPO AVF, there is an additional Ambient Air Temperature Sensor in the Passenger Outside Rearview Mirror. The Engine Control Module (ECM) reads the resistance value of this sensor to determine outside temperature. This temperature reading is only used for powertrain purposes and is not used for the displayed temperature on the Info Display Module.

Thank you for this info, to make sure I’m understanding correctly, now that there is no sensor on mirror, that would mean I would have more issues other than no temp displayed inside of the truck?

JimCost2014 · January 8, 2020

1 hour ago, RyanS said:

Thank you for this info, to make sure I’m understanding correctly, now that there is no sensor on mirror, that would mean I would have more issues other than no temp displayed inside of the truck?

It is possible to just have a bad sensor (the one behind the grill on the passenger side of the truck), but I would still push to see why they cut/spliced things, what is was supposed to fix?

You can take it too another dealer, but most do not like to touch others warranty work that has been done.

TJay74 · January 8, 2020

-38 is the system default for the IAT and or ambient sensor. It is what the ECM defaults to if the sensor is unhooked. It only takes about 2hrs for the sensor to come back online after it has lost power, sometimes even less than that depending on how much drive time the truck is doing.

Personally if it was me I would tell the dealership to keep the truck and not call back until everything works as it should per GM. The wiring harness needs to be replaced, even GM doesnt typically have them cut and splice a harness. It is replaced for this very exact reason. The newer modules in these trucks are very sensitize to voltages and impedance/resistance in the wiring harness. A bad solder joint could cause all sorts of issues for modules as they send data back forth on the CANBUS network the vehicle uses.

RyanS · January 8, 2020

13 hours ago, JimCost2014 said:

It is possible to just have a bad sensor (the one behind the grill on the passenger side of the truck), but I would still push to see why they cut/spliced things, what is was supposed to fix?

You can take it too another dealer, but most do not like to touch others warranty work that has been done.

They cut and spliced because “there was a short in the harness that was extremely hard to get to. That’s why they did an “overlay”. I already tried calling the Chevy dealer, they said they don’t want to touch it. It doesn’t help that I just found out this dealership doesn’t have a diesel mechanic....

JimCost2014 · January 8, 2020

14 minutes ago, RyanS said:

They cut and spliced because “there was a short in the harness that was extremely hard to get to. That’s why they did an “overlay”. I already tried calling the Chevy dealer, they said they don’t want to touch it. It doesn’t help that I just found out this dealership doesn’t have a diesel mechanic....

I think TJay74 has the best advice you are going to get on the site here, sounds like they did a "hack job" and tried to get away with it.

Contact GM customer service to let them know of the work done, and how it was done, get a claim number, then request to speak with the General Manager, or even owner of the dealership.

Be nice, but let everyone know how upset you are with the truck and how it is being fixed.

And really stress with GM customer service, the fact no other dealers will touch the truck now, because of the suspect warranty work that has already been done.