HVAC System - Manual
DTC B0484, B0485, B0486, B0488, B048A, B1000, B1004, B1424, B1425 or B1439
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B0484 00
- Auxiliary Heater System Locked
DTC B0485 00
- Auxiliary Heater Start Counter Overrun
DTC B0486 00
- Auxiliary Heater Cold Blow Time Exceeded
DTC B0488 00
- Auxiliary Heater Overheat Counter Overrun
DTC B048A 00
- Auxiliary Heater Start Time Exceeded
DTC B1000 00
- Electronic Control Unit
DTC B1004 00
- Keep Alive Memory Reset
DTC B1424 00
- Device Voltage Low
DTC B1425 00
- Device Voltage High
DTC B1439 00
- Intermittent Device Voltage Range/Performance
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
Circuit/System Description
The coolant heater has an electronic control unit that monitors voltage level, temperature, time, and the amount of times the coolant heater has started and turned OFF. If an out of range condition is recognized by the coolant heater electronic control module, a code will be set.
Conditions for Running the DTC
Engine is running.
Conditions for Setting the DTC
Fuel operated heater has recognized an out of range condition in the controller.
Action Taken When the DTC Sets
Fuel operated heater is disabled.
Conditions for Clearing the DTC
DTC must be cleared with a scan tool.
Circuit/System Verification
Start the vehicle. Command the coolant heater ON and OFF with a scan tool. The coolant heater should turn ON and OFF with each command.
Component Testing
Important: If an ECM is reflashed or replaced make sure the vehicle is keyed OFF after the reflash or replacement. If the key is not turned OFF code B1004 will set as current.
1. Ignition OFF, disconnect the 10 pin pigtail connector at the coolant heater.
2. Verify that a test lamp illuminates between the voltage supply circuit on the body side of the 10 pin connector and ground.
• If the test lamp does not illuminate, repair the voltage supply circuit for a short to ground or an open/high resistance. If the voltage supply circuit tests normal, replace the controller.
3. Verify that a test lamp illuminates between the ground circuit on the body side of the 10 pin connector and battery voltage.
• If the test lamp does not illuminate, repair the ground circuit for a short to voltage or an open/high resistance. If the ground circuit tests normal, replace the controller.
4. Check the coolant level and flow through the coolant heater.
• If the coolant level or flow is not correct, refer to Cooling System Leak Testing. Component Tests and General Diagnostics
5. Check the combustion air inlet pipe for blockage.
• If the combustion air inlet is blocked, repair or replace the inlet tube. If the combustion air inlet tube is not blocked, replace the controller.
6. Verify that the fuel supply to the coolant heater is correct.
• If the fuel supply is not correct, inspect the fuel lines and replace the fuel pump. Refer to Heater Coolant Heater Fuel Pump Replacement
7. If the coolant heater tests normal, replace the coolant heater.
Repair Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
Heater Coolant Heater Replacement