B046A
DTC B0468 or B046A-B046C
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC B0468 01
- Auxiliary Heater Coolant Pump Control Circuit Short to Battery
DTC B0468 06
- Auxiliary Heater Coolant Pump Control Circuit Low Voltage/Open
DTC B046B 00
- Auxiliary Heater Coolant Pump Feedback Circuit Malfunction
DTC B046C 02
- Auxiliary Heater Coolant Pump Enable Circuit Short to Ground
DTC B046C 05
- Auxiliary Heater Coolant Pump Enable Circuit High Voltage/Open
Circuit/System Description
The auxiliary heater coolant pump is controlled with a pulse-width modulated control sent from the HVAC control module to the auxiliary heater coolant pump. The higher the duty cycle on the control the higher the pump speed. An enable signal from the HVAC control module to the auxiliary heater coolant pump provides overall control of the pump. When voltage is present, the pump can operate. The auxiliary heater coolant pump provides a hard-wired pulse-width modulated feedback signal to the HVAC control module. During normal operation, this feedback signal provides pump speed information.
Conditions for Running the DTC
B0468 01
* The 12 V battery system voltage is greater than 9 V.
* The vehicle is in the RUN power mode.
* The HVAC system is turned ON.
B0468 06
* The 12 V battery system voltage is greater than 9 V.
* The vehicle is in the RUN power mode.
* The HVAC system is turned ON.
B046B 00
* The 12 V battery system voltage is greater than 9 V.
* The vehicle is in the RUN power mode.
* The HVAC system is turned ON.
B046C 02
* The 12 V battery system voltage is greater than 9 V.
* The vehicle is in the RUN power mode.
* The HVAC system is turned ON.
B046C 05
* The 12 V battery system voltage is greater than 9 V.
* The vehicle is in the RUN power mode.
* The HVAC system is turned ON.
Conditions for Setting the DTC
B0468 01
Requested PWM is not zero and the feedback from the Auxiliary Heater is always High.
B0468 06
Feedback from the auxiliary heater voltage is always low or floating.
B046B 00
PWM duty cycle/ frequency out of range
B046C 02
PWM duty cycle/ frequency out of range
B046B 05
PWM duty cycle/ frequency out of range
Action Taken When the DTC Sets
The auxiliary heater coolant pump is disabled.
Conditions for Clearing the DTC
B0468 01
Feedback of auxiliary heater output corresponds with requested PWM signal.
B0468 06
Feedback of auxiliary heater output corresponds with requested PWM signal.
B046B 00
PWM duty cycle / frequency is within defined range
B046C 02
Requested status of the output is ON and feedback shows normal operation
B046B 05
Requested status of the output is OFF and feedback shows normal operation
Reference Information
Schematic Reference
HVAC Schematics
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
* Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module Referencesfor scan tool information
Circuit/System Verification
Vehicle in Service Mode, HVAC system turned ON, with a scan tool, verify that the Auxiliary Heater Coolant Pump Command is between 20%-90% and Auxiliary Heater Coolant Pump Feedback is about 50%
Circuit/System Testing
1. Vehicle OFF, disconnect the harness connector at the G36 auxiliary heater coolant pump.
2. Vehicle OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the ground circuit terminal 4 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the B+ circuit terminal 5 and ground circuit terminal 4.
4. Vehicle in Service Mode, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground circuit terminal 4.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or replace the G36 auxiliary heater coolant pump.
5. Connect a test lamp between the enable circuit terminal 1 and ground circuit terminal 4.
6. Command the Auxiliary Coolant Pump Speed Command OFF (10%) and ON (90%) with a scan tool. Verify the test lamp turns OFF and ON when changing between the commanded states.
• If the test lamp is always illuminated at 10%, test the pump enable circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC control module.
• If the test lamp does not illuminate at 90%, test the pump enable circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K33 HVAC control module.
7. Connect a test lamp between the control circuit terminal 3 and the B+ circuit terminal 5.
8. Command the Auxiliary Coolant Pump Speed Command ON between 20% and 90% with a scan tool. Verify that a test lamp changes illumination between bright (20%) and dim (90%) between the control circuit terminal 3 and the B+ circuit terminal 5.
• If the test lamp is always dim or does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K33 HVAC control module.
• If the test lamp is always bright, test the control circuit for a short to ground. If the circuit tests normal, replace the K33 HVAC control module.
9. Verify the scan tool Auxiliary Coolant Pump Speed Feedback Frequency parameter is less than 10%.
• If greater than the specified range, test the feedback circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K33 HVAC control module.
10. Install a 3 A fused jumper wire between the feedback circuit terminal 2 and the ground circuit terminal 4. Verify the scan tool, Auxiliary Coolant Pump Speed Feedback Frequency parameter is greater than 90%.
• If less than the specified range, test the feedback circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K33 HVAC control module.
11. If all circuits test normal, replace the G36 auxiliary heater coolant pump.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Heater Water Auxiliary Pump Replacement Service and Repair
* Control Module References Control Module Referencesfor HVAC control module replacement, programming and setup