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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 230 (Heating, Ventilation, And Air Conditioning - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Heating Performance Diagnostic

Heating Performance Diagnostic

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
  • The vehicle is equipped with an automatic coolant service fill feature that assists with removing air while filling the cooling system.
  • Use a 50/50 mixture of DEX-COOL antifreeze and clean drinkable water.
  • To ensure proper diagnosis, vehicle must be warmed to 10°C - 21°C (50°- 70°F) degree ambient temperature (shop environment).
  1. Remove the radiator surge tank cap.
  2. Inspect the concentration of the coolant mixture using GE-26568  Coolant and Battery Fluid Tester.
  3. Run Automatic Coolant Service Fill procedure.
  4. With a cold system, add coolant to the fill line on the radiator surge tank.
  5. To activate the automatic coolant service fill feature perform the following steps:
    1. Connect a battery charger to keep the battery charged during the static fill and air removal procedure.
    2. Place the ignition in service mode. Power Mode Description and Operation
    3. Turn off the air conditioning.
    4. Set the parking brake.
    5. Depress the accelerator and brake pedal at the same time for two seconds, then release.
    6. Listen and / or feel for water pump activation and movement of control valves while watching the level of the coolant in the radiator surge tank. The fill and air removal process will run for approximately 15 minutes. If the radiator surge tank is low or empties, turn the ignition off.
    7. Fill the radiator surge tank to the fill line and wait two minutes.
    8. Repeat steps 5.2-5.7 until coolant reaches the fill line.
    9. Install the radiator surge tank cap.
  6. Scan for trouble codes regardless of Malfunction Indicator Lamp (MIL) status. Address any DTCs set. Diagnostic Trouble Code (DTC) List - Vehicle
  7. If equipped, diagnose the Electric Auxiliary Heater.
  8. Verify the heater flow request is active and being received and recognized by using PID/DID list In the chart below.
    1. Determine which Serial Data Bus the vehicle uses; Global A OBD, Global A eOBD, or Global B using PID/DID list shown below. Determine if HEATER FLOW REQUEST is OK or NOT OK. If heater flow signals are OK, the REQUEST should increase with higher HVAC blower motor speed and FEEDBACK should read at least as high as REQUEST on systems with electric main coolant pumps (GAS Active Thermal Management). Please note: On DIESEL ACTIVE THERMAL MANAGEMENT vehicles, since there is a mechanical pump and flow control valve, the estimated flow FEEDBACK should generally follow the REQUEST but there will be an upper limit to the flow available based on the engine RPM.
    2. Check for coolant flow through heater core:
      1. Change settings to full hot, high blower.
      2. Observe "heater flow request" in scan tool to make sure that it increases when changing from cold/low blower to hot/high blower.
      3. Use an infrared thermometer to verify that temperature changes at heater hoses; use a thermometer to verify that temperature changes at vent outlets. Both should coordinate with request to change from cold/low blower to hot/high blower.
    3. IF HEATER FLOW REQUEST IS OK
      1. After the engine warm up, idle the engine and set on low blower. Using a thermometer, confirm that the heater core inlet hose temperature is within 30° of the heater core outlet hose temperature, and that the heater core inlet is within 5-10° of the engine outlet temperature.
      2. If the heater core inlet hose temperature is within 30° of the heater core outlet hose temperature and both feel hot, evaluate the vehicle for air temperature delivery issues (temp doors, etc.).
      3. If the heater core outlet hose temperature is much colder than the heater core inlet hose temperature, Search for Heater Hose/Core blockage by performing visual / tactile inspection of heater hoses and inspect for blockage caused by twists/bends in hoses.
      4. Perform heater core coolant flush and inspect for blockage.
      5. Performing heater hose coolant flush and inspect for blockage.
      6. Run Automatic Coolant Service Fill procedure to de-aerate cooling system.
  9. IF HEATER FLOW REQUEST IS NOT OK AND DOES NOT MOVE AS EXPECTED - Global A OBD - Diagnose the heater core coolant temperature sensors by:
    1. Ensuring correct heater core coolant temperature sensor part numbers are being used, and replace if necessary.
    2. Ensuring proper signal goes blank when heater core coolant temperature sensor is unplugged.
    3. With blower off and engine on, confirm heater core in and out temperatures are approximately within 6°C (43°F) of each other. If not, replace both heater core coolant temperature sensors.
    4. Make sure heater temperature sensors are actually measuring coolant temp (not air, rubber, etc.).
  10. Global A eOBD - Check ECC communication and address the DTCs set.
  11. Global B - Address the DTCs set.
Data Input Signal Serial Data Bus PID Module Data Information Displayed
Heat & Flow Arbitrator Vehicle Configuration Selection Service Data All 372B ECM Determine which system and control scheme is in use in the vehicle.
Arbitrated Heater Minimum Flow rate Request GA, OBD 3720 ECM Final heater flow (Request)
Estimated Heater Core Flow rate Feedback Service Data GA, OBD 3724 ECM Estimated heater flow (Feedback)
Climate Control Heater Minimum Flow Rate Request GB, GA, eOBD 85B1 ECC, BCM Final heater flow (Request)
Estimated Heater Core Coolant Flow rate Feedback Service Data GB, GA, eOBD 85B3 ECC, BCM Estimated heater flow (Feedback)
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