B0166

Diagnostic Trouble Code Chart:

Wiring Schematics:

CIRCUIT DESCRIPTION
The inside air temperature sensor is a thermistor used in order to control the signal voltage in the Electronic Climate Control (ECC) module. The ECC 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 ECC module will receive a high voltage input. If the outside air temperature is hot, the thermistor resistance is low. Therefore, the ECC module will receive a low signal voltage input. Refer to Sensor Resistance Table. Sensor Resistance Table - HVAC System - Automatic

CONDITIONS FOR SETTING THE DTC
When the ignition is ON, the ECC module will detect DTC B0166 any time that CKT 734 is near 5 volts or higher.

ACTION TAKEN WHEN THE DTC SETS
The ECC module will use a default value of 23.8°C (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 may only be cleared by removing and restoring B+ or by using the scan tool.

DIAGNOSTIC AIDS
^ The ECC module may set class 2 lost communication DTCs when the Body Control Module (BCM) or the Vehicle Control Module (VCM) is being reprogrammed. After reprogramming, inspect for DTCs in the ECC 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 ohm. If the resistance is not within specifications, replace the sensor.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step measures the resistance of the inside air temperature sensor.
3. This step inspects for B+ on CKT 734.
4. This step determines if the short to B+ is in CKT 734 or in the ECC module.
6. This step inspects for an open in CKT 552.
7. This step replaces a defective inside air temperature sensor.
8. This step repairs an open in CKT 552.
10. This step inspects for intermittents and tests for a malfunctioning ECC module.
11. This step replaces a defective ECC module.
12. This step inspects for 5 volts on CKT 734.
13. This step determines if the open is in CKT 734 or in the ECC module.