GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0161 Outside Air Temp Sensor Circuit High

Object Number: 283798 Size: LF

Circuit Description

The outside air temperature sensor is a thermistor used to control the signal voltage in the heater and A/C control module. The heater and A/C control supplies a reference voltage (about 5 volts) on CKT 636 to the sensor. When the outside (ambient) air temperature is cold, the thermistor resistance is high. Therefore, the heater and A/C control module will receive a high voltage input. If the outside air temperature is hot, the thermistor resistance is low . Therefore, the heater and A/C control module will receive a low signal voltage input. Refer to Sensor Resistance Table .

Conditions for Setting the DTC

With the ignition ON, the heater and A/C control will detect the DTC B0161 any time that CKT 636 is near 5 volts or higher.

Action Taken When the DTC Sets

The heater and A/C control module will use a default value of 26°F (or 168 A/D counts) until the fault is cleared.

Conditions for Clearing the MIL/DTC

This fault will clear as soon as the fault goes away or has been repaired. The system will then return to normal operation. History DTCs can only be cleared by removing and restoring B+ or by using the scan tool.

Diagnostic Aids
    • The heater and A/C control module may set class 2 lost communication DTCs when the BCM or the VCM is being reprogrammed. After reprogramming, check for DTCs in the heater and A/C control module. Clear any history U DTCs, then resume diagnosis.
    • Visually inspect the sensor connector and harness for corrosion and damage. The resistance value of the sensor must be 300 - 170,000 ohms. Refer to the Temperature vs Resistance Table. If resistance is not within specifications, replace the sensor.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step measures the resistance of the outside air temperature sensor.

    2.

  2. This step inspects for B+ on CKT 636.

    3.

  3. This step determines if the short to B+ is in CKT 636 or in the heater and A/C control module.

    4.

  4. This step inspects for an open in CKT 552.

    5.

  5. This step replaces a defective outside air temperature sensor.

    6.

  6. This step repairs an open in CKT 552.

    7.

  7. This step inspects for intermittents and tests for a malfunctioning heater and A/C control module.

    8.

  8. This step replaces a defective heater and A/C control module.

    9.

  9. This step inspects for 5 volts on CKT 636.

    10.

  10. This step determines if the open is in CKT 636 or in the heater and A/C control module.

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition to the OFF position.
  2. Disconnect the outside air temperature sensor.
  3. Measure the resistance between sensor terminals A and B.
  4. Compare the reading to the temperature/resistance table. Refer to System Performance Test .

Is the resistance within the range specified?

--

Go to Step 2

Go to Step 5

2

  1. Turn the ignition to the ON position.
  2. Measure the voltage at terminal B of the outside air temperature sensor harness connector and ground.

Is the battery voltage within the specified range?

9-16 V

Go to Step 3

Go to Step 9

3

Inspect CKT 636 (DK GRN/WHT) for a short to B+.

Was a short to B+ repaired in CKT 636 (DK GRN/WHT)?

--

Go to Diagnostic System Check

--

4

Inspect for continuity to ground at terminal A of the outside air temperature sensor harness connector and ground.

Is there continuity?

--

Go to Step 7

Go to Step 6

5

Replace the sensor.

Is the repair complete?

--

Go to Diagnostic System Check

--

6

Inspect CKT 552 (BLK) for an open.

Was an open repaired in CKT 552 (BLK)?

--

Go to Diagnostic System Check

Go to Step 8

7

  1. Turn the ignition to the OFF position.
  2. Reconnect the outside air temperature sensor.
  3. Reconnect the heater and A/C control module.
  4. Turn the ignition to the ON position.
  5. Clear any heater and A/C control module DTCs.

Does the DTC reset?

--

Go to Step 8

Go to Intermittents and Poor Connections Diagnosis

8

Replace the heater and A/C control module.

Is the repair complete?

--

Go to Diagnostic System Check

--

9

Use a J 39200 in order to ground and measure the voltage on terminal B of the outside air temperature sensor connector.

Is the voltage within the specified range?

4-6V

Go to Step 4

Go to Step 10

10

Inspect CKT 636 (DK GRN/WHT) for an open.

Was an open repaired in CKT 636 (DK GRN/WHT)?

--

Go to Diagnostic System Check

Go to Step 8