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Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 4WD 🢒 DTC 🢒 DTC B0175 Output Air Temp Sensor 1 Circuit Low

DTC B0175 Output Air Temp Sensor 1 Circuit Low Upper


Object Number: 283799 Size: LF

Circuit Description

The passenger compartment temperature sensor #1 (upper) is a thermistor used to control the signal voltage in the heater and A/C control module. The heater and A/C control module supplies a reference voltage (about 5 volts) on CKT 404 to the sensor. When the upper duct 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 upper duct air temperature is hot, the thermistor resistance is low. Therefore, the heater and A/C control module will receive a low signal voltage input. The output air temperature sensor #1 (upper) is used to enhance the temperature control. Refer to Sensor Resistance Table .

Conditions for Setting the DTC

When the ignition is ON, the heater and A/C control module will detect DTC B0175 any time that CKT 404 is at or near zero voltage.

Action Taken When the DTC Sets

The heater and A/C control module will use a default value of 10 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, inspect for DTCs in the heater and A/C control module. Clear any history U DTCs, then resume diagnostics.
    • Visually inspect the sensor connector and harness for corrosion and damage. The resistance value of the sensor must be 334-100,865 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 resistance of output air temperature sensor #1.

    2.

  2. This step inspects for a short to ground in CKT 404.

    3.

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

    4.

  4. This step repairs the short to ground in CKT 404.

    5.

  5. This step replaces defective output air temperature sensor #1.

    6.

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

Step

Action

Value(s)

Yes

No

1

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

Is the resistance within the specified range?

--

Go to Step 2

Go to Step 5

2

  1. Disconnect the heater and A/C control module.
  2. Inspect for a short to ground in CKT 404 at terminal C2 of the heater and A/C control module harness connector.

Does the DMM indicate less than the specified value?

5 ohms

Go to Step 4

Go to Step 3

3

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

Does the DTC reset?

--

Go to Step 6

Go to Intermittents and Poor Connections Diagnosis

4

Repair the short to ground in CKT 404 (BRN).

Is the repair complete?

--

Go to Diagnostic System Check

--

5

Replace output air temperature sensor #1.

Is the repair complete?

--

Go to Diagnostic System Check

--

6

Replace the heater and A/C control module.

Is the repair complete?

--

Go to Diagnostic System Check

--