GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0166 Pass Compart Temp Sensor 1 Circuit High

Object Number: 283802 Size: MF

Circuit Description

The passenger compartment temperature sensor #1 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 734 to the sensor. When the inside 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

When the ignition is ON, the heater and A/C control module will detect DTC B0166 any time that CKT 734 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 75°F (or 88 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 300-170,000 ohms. 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 passenger compartment temperature sensor #1.

    2.

  2. This step inspects for B+ on CKT 734.

    3.

  3. This step determines if the short to B+ is in CKT 734 or in the control head.

    4.

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

    5.

  5. This step replaces a defective passenger compartment temperature sensor #1.

    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 734.

    10.

  10. This step determines if the open is in CKT 734 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 passenger compartment temperature sensor #1
  3. Measure the resistance between passenger compartment sensor terminals A and D.
  4. Compare the reading to the Temperature/Resistance table. Refer to Sensor Resistance Table .

Is the resistance within the specified range?

--

Go to Step 2

Go to Step 5

2

  1. Turn the ignition to the ON position.
  2. Measure the voltage at terminal A of the passenger compartment temperature sensor harness connector and ground.

Does the DMM indicate the specified voltage?

9-16 V

Go to Step 3

Go to Step 9

3

Inspect CKT 734 (DK GRN) for a short to B+.

Is the repair complete?

--

Go to Diagnostic System Check

Go to Step 8

4

Inspect for continuity to ground at terminal D of the passenger compartment temperature sensor harness connector and ground.

Is continuity indicated?

--

Go to Step 7

Go to Step 6

5

Replace the passenger compartment temperature sensor #1.

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 passenger compartment temperature sensor #1.
  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 Wiring Systems

8

Replace the heater and A/C control module.

Is the repair complete?

--

Go to Diagnostic System Check

--

9

Use a J 39200 DMM in order to ground and measure the voltage on terminal A of the passenger compartment temperature sensor #1.

Is the voltage reading within the specified range?

4-6 V

Go to Step 4

Go to Step 10

10

Inspect CKT 734 (DK GRN) for an open.

Was an open repaired in CKT 734 (DK GRN)?

--

Go to Diagnostic System Check

Go to Step 8