• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

When the refrigerant system is undercharged, the system is not able to meet operational performance targets. The information from sensors in the system are used to calculate two indicators of system efficiency: superheat and subcool.

Superheat is a measurement of the temperature of the refrigerant vapor above its boiling point. A superheat that is too high for the operating conditions indicates there is not enough refrigerant flowing through the evaporator (or chiller).

Subcool is a measurement of the temperature of the refrigerant liquid below its condensing point. A subcool that is too low for the operating conditions indicates there is not enough refrigerant available at the expansion valves.

Either condition can result in poor system performance. If the calculated superheat exceeds a value and the calculated subcool is less than a threshold, the system will take action through various controls to attempt to correct the situation. If the attempts to remedy the system operation do not result in the system operating within tolerances, the DTC will set.

The refrigerant system is monitored for faults under differing conditions:

The purpose of this monitor is to capture a large leak. The diagnostic is run after the system has been off for a specified time (approximately 4 hours), and checks all three pressure sensors values. If all the pressure sensor values are below the failure threshold, the DTC sets.

This monitor is run during system startup, when the compressor takes multiple startup attempts. It checks if the system is able to build sufficient pressure, increase compressor out temperature, increase expansion valve in temperature and decrease compressor in superheat in consecutive startup attempts. If the system doesn't improve after multiple attempts, the DTC sets.

This monitor is run in all ambient temperatures, when cabin heating, cabin cooling, and/or powertrain cooling are requested. It monitors the subcool going into the expansion valves and the superheats leaving the expansion valves. If the values exceed the failure threshold for a specified time, on 4 unique occasions, the DTC sets.

This monitor is run in cold ambient temperatures: below approximately 10°C (50°F), when only cabin heating is requested. It monitors the subcool going into the expansion valves and the superheats leaving the expansion valves. while also monitoring if cabin heating temperature is meeting the target. If all values are failing their respective failure thresholds for a specified time, on 4 unique occasions, the DTC sets.

This monitor is run in mild ambient conditions: approximately 5–20 °C (41–69 °F), when both cabin heating and cooling are requested simultaneously (e.g. the customer requests heat in mild temps where the risk for window fogging is high, so the system cools the air to reduce moisture). If high side and low side pressures fall below a failure threshold, compressor in superheat exceeds a failure threshold, expansion valve in subcool drops below a failure threshold and if cabin heating temperature is not meeting the target for a specified time, on 4 unique occasions, the DTC sets.

• The K16 Battery Energy Control Module is awake and communicating
• 12 V battery system voltage is greater than 10 V
• DTCs B2BA7, B2BA8, B2BA9, B2BAA, B2BAB, B2BAC, B2BAD, B2BAE, B2BAF, B2BB0, B2BB1, B2BB2, B2BB3, B3A00, B3A02, B3A03, B3A0C, B3A0D, B3A11, B3A17, B3A5C, B3A5D, B3A65, B3A66, B3A69, B3A6B, B3A6C, B3A6D, B3A6E, P0530, P0EBD, P0EBE, P0EBF, P0EC2, P0EC3, P0EC4, P1F0A, P151C, P191D, P191E, P191F, P1920, P1C00, P1C01, P1C08, P1C09, P1C24, P1C25, P1C26, P2517, P2518, P293C, P293D, P293E, P293F, U046C, U062C, U062E, U06A5, U13C2, U13C4 or U016B, are not set.

AND one or more of the following has occurred:

• Refrigerant system has been off for greater than 4 hours
• Outside Air Temperature is greater than 0°C (32°F)
• High Side Pressure, High Side Pressure 2 and Low Side Pressure sensor temperatures are greater than 0°C (32°F)

• Outside Air Temperature is greater than −25°C (−13°F)

• Compressor active for greater than 30 seconds
• Chiller Refrigerant Expansion Valve is greater than 25% and Evaporator Refrigerant Expansion Valve is greater than 30%

• Outside Air Temperature is below approximately 10°C (50°F)
• Compressor active for greater than 30 seconds
• Chiller Refrigerant Expansion Valve is greater than 15% and Evaporator Refrigerant Expansion Valve is greater than 50%
• Cabin heating requested

• Outside Air Temperature is between approximately 5–20°C (41–69°F)
• Compressor active for greater than 30 seconds
• Chiller Refrigerant Expansion Valve is greater than 10% and Evaporator Refrigerant Expansion Valve is greater than 10%
• Cabin heating and cooling is requested

• High Side Pressure, High Side Pressure 2 and Low Side Pressure sensor temperatures are less than expected values for the conditions.

• High Side Pressure, High Side Pressure 2 and Low Side Pressure fail to increase by more than 25% on subsequent startups
• Compressor Out (temperature #2) refrigerant temperature fails to increase by more than 15°C (27°F)
• Expansion Valve In (temperature #3) refrigerant temperature fails to increase by more than 8°C (46°F)
• Compressor in superheat decreases by less than 4°C (39°F)

• The calculated chiller superheat temperature OR the calculated evaporator superheat temperature exceeds the expected value by 10°C (18°F)
• The calculated high side subcool temperature is less than the expected value

• The calculated chiller superheat temperature OR the calculated evaporator superheat temperature exceeds the expected value by 10°C (18°F)
• The calculated high side subcool temperature is less than the expected value
• Heating condenser out temperature (temp #6) is more than 12°C (22°F) below target

• The compressor in superheat temperature exceeds the expected value by 10°C (18°F)
• The calculated high side subcool temperature is less than the expected value
• Heating condenser out temperature (temp #6) is more than 12°C (22°F) below target
• High Side Pressure 2 and Low Side Pressure are less than the calibrated threshold
• Low Side Pressure is less than 380 kPA (55 PSI)

• DTC Type A
• Refrigerant system is disabled for the key cycle the DTC is active

DTC Type A

• This DTC may be caused by an inaccurate sensor.
• This DTC may be set by an incorrectly installed check valve. Inspect the check valves for correct orientation

HVAC Schematics

Master Electrical Component List

Automatic HVAC Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References for scan tool information

1. Vehicle In Service Mode
2. Verify DTCs P0071–P0074 are not set.
• If DTCs P0071–P0074 are set

  Refer to DTC P0071-P0074.

• If DTCs P0071–P0074 are not set
3. Verify DTCs U1104, U13CC, or U153B are not set.
• If any of the DTCs are set

  Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• If none of the DTCs are set
4. Verify the Passenger Compartment Air Temperature Sensor Voltage parameter does not equal a value of −40°C (−40°F)

   Refer to Temperature Versus Voltage - Passenger Compartment Air Temperature Sensor

• If the Passenger Compartment Air Temperature Sensor Voltage parameter equals a value of −40°C (−40°F)

  Replace the B10E Sun Load and Ambient Light and Charge Indicator Sensor.

• If the Passenger Compartment Air Temperature Sensor Voltage parameter does not equal a value of −40°C (−40°F)
5. Inspect the system for leaks, refer to Leak Testing. Verify no leaks are present.
• If any leaks are found

  Perform the necessary repairs, then recharge the refrigerant system, refer to Refrigerant Recovery and Recharging.

• If no leaks are found
6. Refer to Air Conditioning (A/C) System Performance Test
• If any issues are found

  Perform the necessary repairs.

• If no issues are found
7. A fault is not currently present and may be an intermittent condition. Check for bulletins or contact the Technical Assistance Center.

Perform the Diagnostic Repair Verification after completing the repair.

• HVAC Component Replacement Reference
• Control Module References for control module replacement, programming, and setup