Where's ambient air temperature sensor circuit on a 2006 ml 350

Did you by chance check for DTC'S diagnostic trouble codes?

Instrument Cluster Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1255 Air Temperature External Sensor Circuit Open Instrument cluster Go To Pinpoint Test E . B1257 Air Temperature External Sensor Circuit Short to Ground Instrument cluster Go To Pinpoint Test E . B2097 Compass Module Failure Instrument cluster Go To Pinpoint Test B . U2013 Compass Module - No Response Instrument cluster Go To Pinpoint Test B . All Other DTCs - Instrument cluster REFER to Section 419-10 .

Supposedly blinking ac indicates ambient air sensor needs replaced ?????? no it doesn't ! Why don't you do yourself a favor an take it to a qualified repair shop that knows how to diagnose it correctly . Hooking up a factory or professional scan tool an checking for code's is the first thing to do. The way to know if a sensor has a malfunction is by A stored DTC - diagnostic trouble code .
DTC Descriptors
DTC B0158 02: Outside Air Temperature Sensor Circuit Short to Ground
DTC B0158 05: Outside Air Temperature Sensor Circuit Short to Battery or Open
DTC B0163 02: Passenger Compartment Temp Sensor 1 Circuit Short to Ground
DTC B0163 05: Passenger Compartment Temp Sensor 1 Circuit Short to Battery or Open
DTC B0168 02: Passenger Compartment Temp Sensor 2 Circuit Short to Ground
DTC B0168 05: Passenger Compartment Temp Sensor 2 Circuit Short to Battery or Open
DTC B0173 02: Output Air Temperature Sensor 1 Circuit Short to Ground
DTC B0173 05: Output Air Temperature Sensor 1 Circuit Short to Battery or Open
DTC B0178 02: Output Air Temperature Sensor 2 Circuit Short to Ground
DTC B0178 05: Output Air Temperature Sensor 2 Circuit Short to Battery or Open
DTC B0509 02: Output Air Temperature Sensor 3 Circuit Short to Ground
DTC B0509 05: Output Air Temperature Sensor 3 Circuit Short to Battery or Open
DTC B0514 02: Output Air Temperature Sensor 4 Circuit Short to Ground
DTC B0514 05: Output Air Temperature Sensor 4 Circuit Short to Battery or Open
DTC B3578 02: Output Air Temperature Sensor 6 Circuit Short to Ground
DTC B3578 05: Output Air Temperature Sensor 6 Circuit Short to Battery or Open
DTC B3583 02: Output Air Temperature Sensor 7 Circuit Short to Ground
DTC B3583 05: Output Air Temperature Sensor 7 Circuit Short to Battery or Open

Manual or automatic climate control ?
Have you had the HVAC control panel checked for DTC'S - diagnostic trouble codes ?

Air Temperature Sensors
The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
• Ambient Air Temperature Sensor
• Inside Air Temperature Sensor Assembly
• Upper Left Air Temperature Sensor
• Upper Right Air Temperature Sensor
• Lower Left Air Temperature Sensor
• Lower Right Air Temperature Sensor
A signal and a low-reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40°C (-40°F) to 101°C (215°F). The sensor signal varies between 0-5 volts.
The input of the duct air temperature sensors are different from the ambient and inside sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.

• DTC B0174 Output Air Temperature Sensor (Upper Left) Circuit Range/Performance
• DTC B0179 Output Air Temperature Sensor 2 (Lower Left) Circuit Range/Performance
• B0414 is for the left air temperature actuator.
B0408 is for the left air temperature actuator.
DTC B0989 Output Air Temperature Lower Sensors Correlation
The HVAC control module monitors the upper left and upper right duct temperature sensors when the mode switch is in the VENT or BI-LEVEL positions. The HVAC control module monitors the lower left and lower right duct temperature sensors when the mode switch is in the DEFOG, FLOOR or FRONT DEFROST positions. The duct sensors are used to measure the temperature of the air exiting the ducts to help maintain a consistent cabin air temperature. These duct sensor inputs provide the HVAC control module a way to determine if the engine needs to be started to maintain a specific air temperature. If an upper duct sensor circuit failure is detected the HVAC module will not request an engine start to help cool the cabin. A lower duct sensor circuit failure will not prevent the engine from starting.
DTC B0990 Output Air Temperature Upper Sensors Correlation
Your best bet , take it to a qualified repair shop .

Ambient Air Temperature Sensor (UH9)
At the front of the vehicle, at the lower left side of the front bumper bar
Ambient Air Temperature Sensor (UH9)
Pin
Wire
Circuit
Function
A
0.35 L-GN/BK
735
Ambient Air Temperature Sensor Signal
B
0.35 YE
61
Low Reference

P0072 - Ambient Air Temperature Sensor Circuit Low Input

- Faulty ambient air temperature sensor
- Ambient air temperature sensor harness is open or shorted
- Ambient air temperature sensor circuit poor electrical connection

- Faulty ambient air temperature sensor
- Ambient air temperature sensor harness is open or shorted
- Ambient air temperature sensor circuit poor electrical connection

P0050 HO2S Heated Oxygen Sensor -Control Circuit (Bank 2 Sensor 1)

P0051 HO2S Heated Oxygen Sensor -Control Circuit Low (Bank 2 Sensor 1)

P0052 HO2S Heated Oxygen Sensor -Control Circuit High (Bank 2 Sensor 1)

P0053 HO2S Heated Oxygen Sensor -Resistance (Bank 1 Sensor 1)

P0054 HO2S Heated Oxygen Sensor -Resistance (Bank 1 Sensor 2)

P0055 HO2S Heated Oxygen Sensor -Resistance (Bank 1 Sensor 3)

P0056 HO2S Heated Oxygen Sensor -Control Circuit (Bank 2 Sensor 2)

P0057 HO2S Heated Oxygen Sensor -Control Circuit Low (Bank 2 Sensor 2)

P0058 HO2S Heated Oxygen Sensor -Control Circuit High (Bank 2 Sensor 2)

P0059 HO2S Heated Oxygen Sensor -Resistance (Bank 2 Sensor 1)

P0060 HO2S Heated Oxygen Sensor -Resistance (Bank 2 Sensor 2)

P0061 HO2S Heated Oxygen Sensor -Resistance (Bank 2 Sensor 3)

P0062 HO2S Heated Oxygen Sensor -Control Circuit (Bank 2 Sensor 3)

P0063 HO2S Heated Oxygen Sensor -Control Circuit Low (Bank 2 Sensor 3)

P0064 HO2S Heated Oxygen Sensor -Control Circuit High (Bank 2 Sensor 3)

P0065 Air Assisted Injector -Range/Performance

P0066 Air Assisted Injector -Circuit Malfunction or Circuit Low

P0067 Air Assisted Injector -Circuit High

P0068 (MAP) Manifold Absolute Pressure /(MAF) Mass Air Flow - Throttle Position

Correlation

P0069 (MAP) Manifold Absolute Pressure / (BARO)Barometric Pressure Correlation

P0070 Ambient/Outside Air Temperature Sensor -Circuit Malfunction

P0071 Ambient/Outside Air Temperature Sensor -Range/Performance Problem

P0072 Ambient/Outside Air Temperature Sensor -Circuit Low Input

P0073 Ambient/Outside Air Temperature Sensor -Circuit High Input

P0074 Ambient/Outside Air Temperature Sensor -Circuit Intermittent

P0075 Intake Valve Control Solenoid Circuit Malfunction (Bank 1)

P0076 Intake Valve Control Solenoid Circuit Low (Bank 1)

P0077 Intake Valve Control Solenoid Circuit High (Bank 1)

P0078 Exhaust Valve Control Solenoid Circuit Malfunction (Bank 1)

P0079 Exhaust Valve Control Solenoid Circuit Low (Bank 1)

P0080 Exhaust Valve Control Solenoid Circuit High (Bank 1)

P0081 Intake valve Control Solenoid Circuit Malfunction (Bank 2)

P0082 Intake Valve Control Solenoid Circuit Low (Bank 2)

P0083 Intake Valve Control Solenoid Circuit High (Bank 2)
P0084 Exhaust Valve Control Solenoid Circuit Malfunction (Bank 2)

Well, I would say that it means that SOMEBODY is confused!

Diagnostic Test Code (DTC) P0072 is defined by SAE J2012 as "Ambient Air Temperature Sensor Circuit Low" DTC P0073 is defined as "Ambient Air Temperature Sensor Circuit High"

I do not know how the ambient air temperature sensor circuit could be faulted both HIGH and LOW at the same time.

The only thing I have ever seen cause something like this is when people try to install aftermarket "performance chips" on their vehicles which "lie" to the computer about what the ambient air temperature is.

A educated guess I would have to say there is a problem with HVAC control module ! electronics you know ! But that's not the way to do things ! There could be codes stored in the module. The Chevy dealer my have a reflash bulletin for this problem . Then can reflash , reprogram the control module ! The first place to start is checking for codes in the HVAC module.
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal.
Air Temperature Sensors The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
?€¢
Ambient Air Temperature Sensor

?€¢
Inside Air Temperature Sensor Assembly

?€¢
Inside Air Temperature Sensor Assembly-Auxiliary

?€¢
Upper Left Air Temperature Sensor

?€¢
Upper Right Air Temperature Sensor

?€¢
Lower Left Air Temperature Sensor

?€¢
Lower Right Air Temperature Sensor

?€¢
Upper Air Temperature Sensor-Auxiliary

?€¢
Lower Air Temperature Sensor-Auxiliary
A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40?° to +101?°C (-40?° to +215?°F). The sensor signal varies between 0-5 volts.
The input of the duct air temperature sensors are different from the ambient and inside air temperature sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.
If the HVAC control module or auxiliary HVAC control module detects a malfunctioning sensor, then the control module software will use a defaulted air temperature value. The default value for the ambient and inside air temperature sensors will be displayed on the scan tool. The default value for the duct air temperature sensors will not be displayed on the scan tool. The scan tool parameter for the duct air temperature sensors are the actual state of the signal circuit. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.
The ambient air temperature sensor mounts underhood and can be affected by city traffic, by idling, and by restarting a hot engine. Therefore, the HVAC control module filters the value of the ambient air temperature sensor for temperature display. The ambient air temperature value is updated under the following conditions: Or you can just buy a new control module an hope that it fixes it. $89.00 at www.partsgeek.com

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