2010 Cadillac CTS Sedan AWD V6-3.0L Page 1553
1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
2. Ignition ON, test for 4.8-5.2 V between each of the affected 5 V reference circuits and ground.
瀚慖f the voltage is less than the specified range, test for a short to ground or for an open between the ECM and the affected circuit splice. If
the circuit tests normal, replace the K20 ECM.
瀚慖f the voltage is greater than the specified range, test for a short to voltage on the 5 V reference circuit. If the circuit tests normal, replace
the K20 ECM.
Note: A short to voltage on the signal circuit of certain components may cause this DTC to set.
3. Connect each component associated with the affected 5 V reference circuit one at a time while monitoring the appropriate scan tool 5 V
Reference Circuit Status parameter. The parameter should continue to display OK.
瀚慖f the parameter displays Fault when a component is connected, test the signal circuit of that component for a short to voltage. If the
circuit tests normal, replace the component.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Fuel Tank Pressure Sensor Replacement (See: Powertrain Management/Computers and Control Systems/Fuel Tank Pressure Sensor/Service
and Repair)
* Fuel Pressure Sensor Replacement - Fuel Injection Fuel Rail (LF1) (See: Powertrain Management/Fuel Delivery and Air Induction/Fuel
Pressure Sensor/Switch/Service and Repair)Fuel Pressure Sensor Replacement - Fuel Injection Fuel Rail (LLT) (See: Powertrain
Management/Fuel Delivery and Air Induction/Fuel Pressure Sensor/Switch/Service and Repair)
* Engine Oil Pressure Sensor and/or Switch Replacement (See: Engine, Cooling and Exhaust/Engine/Engine Lubrication/Oil Pressure
Sensor/Service and Repair)
* Camshaft Position Sensor Replacement - Bank 1 (Right Side) Intake (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 1 (Right Side) Intake)
* Camshaft Position Sensor Replacement - Bank 1 (Right Side) Exhaust (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 1 (Right Side) Exhaust)
* Camshaft Position Sensor Replacement - Bank 2 (Left Side) Intake (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 2 (Left Side) Intake)
* Camshaft Position Sensor Replacement - Bank 2 (Left Side) Exhaust (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 2 (Left Side) Exhaust)
* Accelerator Pedal Position Sensor Replacement (See: Powertrain Management/Computers and Control Systems/Accelerator Pedal Position
Sensor/Service and Repair)
* Throttle Body Assembly Replacement (LF1) (See: Powertrain Management/Fuel Delivery and Air Induction/Throttle Body/Service and
Repair/Removal and Replacement)Throttle Body Assembly Replacement (LLT) (See: Powertrain Management/Fuel Delivery and Air
Induction/Throttle Body/Service and Repair/Removal and Replacement)
* Crankshaft Position Sensor Replacement (See: Powertrain Management/Computers and Control Systems/Crankshaft Position
Sensor/Service and Repair)
* Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement (See: Heating and Air Conditioning/Refrigerant Pressure Sensor /
Switch/Service and Repair)
* Clutch Pedal Position Switch Replacement (See: Powertrain Management/Transmission Control Systems/Sensors and Switches -
Transmission and Drivetrain/Sensors and Switches - M/T/Clutch Pedal Position Sensor / Switch/Service and Repair)
P0645
DTC P0645, P0646, or P0647
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0645
- Air Conditioning (A/C) Clutch Relay Control Circuit
DTC P0646
- Air Conditioning (A/C) Clutch Relay Control Circuit Low Voltage
