2010 Cadillac CTS Sedan AWD V6-3.6L Page 647
* The DTC will become history if the HVAC control module no longer detects a failure.
* The history DTC will clear after 50 fault-free ignition cycles.
Reference Information
Schematic Reference
HVAC Schematics (See: Heating and Air Conditioning/Diagrams/Electrical Diagrams)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Automatic HVAC Description and Operation (See: Heating and Air Conditioning/Description and Operation/HVAC - Automatic)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool A/C Evaporator Temperature Sensor parameter. The reading should be between -35掳C (-39掳F) and 98掳C (208掳F)
and change with evaporator temperature changes.
Circuit/System Testing
Important: If the evaporator air temperature sensor has an out of range condition caused by a short to voltage, short to ground, open/high
resistance or if the DTC is set, the scan tool will display 0掳C (32掳F).
1. Ignition OFF, disconnect the harness connector at the evaporator temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 and ground.
瀚慖f greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC
control module.
3. Ignition ON, test for 4.8-5.2 volts between the low reference circuit terminal 2 and the signal circuit terminal 1.
瀚慖f less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the
HVAC control module.
瀚慖f greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control
module.
4. If all circuits test normal, test or replace the evaporator air temperature sensor.
Component Testing
1. A thermometer can be used to test the sensor off the vehicle in warn and or cold water. Sensor Resistance Table (See: Heating and Air
Conditioning/Specifications/Electrical Specifications) for this test.
2. Test the evaporator air temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
3. Compare the readings with the Temperature VS Resistance table and verify that the resistance is within 5 percent of the specification.
瀚慖f not within the specified range, replace the sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Evaporator Air Temperature Sensor Replacement (See: Heating and Air Conditioning/Evaporator Temperature Sensor / Switch/Service and
Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for HVAC control module replacement, setup, and
