Radio temp display driving me nuts

[zmnypit]

In my 15 Sierra 2500 Denali since owning the temp display has been wrong. For example it's currently 86* here today, get in the truck at lunch and the temp display says -40* making the auto feature on the ac useless. I've replaced both sensors as well as drove in the interstate for 20min or longer. One in the mirror and one behind the grille with same results. It will only display the correct temp for a sec then as soon as I slow it stop goes back crazy. Almost 90* today and the instrument cluster says "ice possible drive with care"

 

Is there a way to reset the system or could it be something else? Maybe another sensor I'm unaware of?  Thanks

[newdude]

Most likely a bad sensor.  Seeing you have one in the mirror, I assume you are diesel?  The one in the mirror is an ambient temp sensor feed for the ECM for use in powertrain data and function.  

 

The radio temp display uses the one behind the grille.  A poor functioning sensor can set codes as well as either a P0071-P0074 code or B0158 code.  

Edited May 29, 2020 by newdude

[zmnypit]

38 minutes ago, newdude said:

Most likely a bad sensor.  Seeing you have one in the mirror, I assume you are diesel?  The one in the mirror is an ambient temp sensor feed for the ECM for use in powertrain data and function.  

 

The radio temp display uses the one behind the grille.  A poor functioning sensor can set codes as well as either a P0071-P0074 code or B0158 code.  

Diesel yes. I've replaced both sensors last year with no change in issues. I guess I will order another just to verify. Also I have no codes other than the occasional U0198 during colder months. 

[newdude]

1 hour ago, zmnypit said:

Diesel yes. I've replaced both sensors last year with no change in issues. I guess I will order another just to verify. Also I have no codes other than the occasional U0198 during colder months. 

 

Hmmm.  Well, the data from the sensor flows through the IPC then to the radio, so perhaps there is an intermittent fault on a data line or the cluster.

 

Quote

 

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.

 

Outside Air Temperature Display Malfunction (2500/3500 series)

DTC Descriptors

DTC B0158 02

Ambient Air Temperature Sensor Circuit Short to Ground

DTC B0158 05

Ambient Air Temperature Sensor Circuit High Voltage/Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Signal	B0158 02	1 or B0158 05	B0158 05	1
Low Reference	—	B0158 05	—	—
1. Outside Air Temperature Display Malfunction

Circuit/System Description

The B9 Ambient Air Temperature Sensor is located behind the grille. The instrument cluster monitors the ambient air temperature sensor with a low reference circuit and signal circuit. The instrument cluster monitors the voltage drop across the sensor, which is inversely proportional to temperature. When the ambient air temperature is cold, the resistance of the sensor is high. When the ambient air temperature is warm, the resistance of the sensors is low. The instrument cluster converts the voltage value to a temperature value and displays the temperature.

Conditions for Running the DTC

The system voltage is between 9–16 V.

Conditions for Setting the DTC

B0158 02

The instrument cluster detects the sensor signal is more than 88°C (190°F) .

 

B0158 05

The instrument cluster detects the sensor signal is less than −40°C (−40°F).

 

Action Taken When the DTC Sets

The instrument cluster uses a default air temperature value for further calculations. The instrument cluster will display −°C (−°F). A/C compressor engagement may be disabled.

Conditions for Clearing the DTC

The DTC will become history if the instrument cluster no longer detects a malfunction.

Diagnostics Aids

The displayed temperature is a filtered value that updates periodically while driving. The value rarely changes when the vehicle is parked.

For an overview of the component/system, refer to: Instrument Cluster Description and Operation

Circuit/System Verification

Note: For vehicles with RPO AVF, ensure that the Body Control Module and Instrument Cluster have been programmed with the latest calibrations before proceeding with Circuit/System Verification and Circuit/System Testing.

1. Ignition ON.
2. Verify the scan tool Instrument Cluster Ambient Air Temperature parameter is between −40°C (−40°F) and +88°C (+190°F) and changes with air temperature changes.
   • If not between −40°C (−40°F) and +88°C (+190°F) or changes with air temperature changes

     Refer to Circuit/System Testing.

   • If between −40°C (−40°F) and +88°C (+190°F) and changes with air temperature changes
3. All OK.

Circuit/System Testing

Note: Circuit/System Verification must be performed before proceeding with Circuit/System Testing.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B9 Ambient Air Temperature Sensor. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit terminal B/2 and ground.
   • If 10 Ω or greater
   1. Ignition OFF, disconnect the harness connector at the P16 Instrument Cluster.
   2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the P16 Instrument Cluster.
   • If less than 10 Ω
3. Ignition ON.
4. Verify the scan tool Ambient Air Temperature parameter is greater than 98%.
   • If 98% or less
   1. Ignition OFF, disconnect the harness connector at the P16 Instrument Cluster.
   2. Test for infinite resistance between the signal circuit terminal A/1 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the P16 Instrument Cluster.
   • If greater than 98%
5. Install a 3 A fused jumper wire between the signal circuit terminal A/1 and the low reference circuit terminal B/2.
6. Verify the scan tool Ambient Air Temperature parameter is less than 8%.
   • If 8% or greater
   1. Ignition OFF, disconnect the harness connector at the P16 Instrument Cluster, ignition ON.
   2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
   3. Ignition OFF
   4. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the P16 Instrument Cluster.
   • If less than 8%
7. Connect the component: B9 Ambient Air Temperature Sensor
8. Operate the vehicle within the Conditions for Running the DTC.
9. Verify the DTC does not set.
   • If the DTC sets

     Replace the component: B9 Ambient Air Temperature Sensor

   • If the DTC is not set
10. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Displays and Gauges Component Replacement Reference
• Control Module References for instrument cluster replacement, programming and setup

 

 

 

[zmnypit]

Swapped the sensor today while 90* took it on a test run and with 2-3min was say 27* so no luck on a new sensor. Guess it will have to head to the dealership to diagnose