B0180

Diagnostic Trouble Code Chart:

Wiring Schematics:

CIRCUIT DESCRIPTION
The lower discharge 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 405 to the sensor. When the lower duct air temperature is cold, the thermistor resistance is high. Therefore, the ECC module will receive a high voltage input. If the lower duct air temperature is hot, the thermistor resistance is low. Therefore, the ECC module will receive a low signal voltage input. The lower discharge air temperature sensor is used in order to enhance the temperature control. 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 this fault any time that CKT 405 is at or near 5 volts or higher.

ACTION TAKEN WHEN THE DTC SETS
The ECC 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 DTC B0180 disappears or is 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 334-100,885 ohm. Refer to Sensor 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.
2. This step measures the resistance of the lower discharge air temperature sensor.
3. This step inspects for a short to ground in CKT 405.
4. This step inspects for intermittents and tests for a malfunctioning ECC module.
5. This step repairs the short to ground in CKT 405.
6. This step replaces a defective lower discharge air temperature sensor.
7. This step replaces a defective ECC module.