HVAC - Manual
DTC B048D or B048E
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 Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B048D 01
-
Auxiliary Heater Temperature Command Circuit Short to Battery
DTC B048D 06
-
Auxiliary Heater Temperature Command Circuit Low Voltage/Open
DTC B048E 00
-
Auxiliary Heater System Malfunction
Diagnostic Fault Information
Circuit/System Description
The HVAC control module sends a pulse width modulation (PWM) signal to the electrical auxiliary heater, if the interior temperature is too low and additional heat is requested. The request signal from the HVAC control module, battery positive, ignition and ground circuits enable the electrical auxiliary heater to operate. Through the signal circuit the electrical auxiliary heater sends via a PWM signal the current status to the HVAC control module.
Conditions for Running the DTC
* Ignition ON
* The HVAC control module is ON.
* The electrical auxiliary heater is ON.
Conditions for Setting the DTC
B048D 01
The voltage at the HVAC control module output to the electrical auxiliary heater is always high.
B048D 06
The voltage at the HVAC control module output to the electrical auxiliary heater is always low or floating.
B048E 00
The feedback signal of the electrical auxiliary heater does not correspond with the requested PWM signal.
Action Taken When the DTC Sets
The electrical auxiliary heater is inoperative.
Conditions for Clearing the DTC
The feedback signal of the electrical auxiliary heater corresponds with the requested PWM signal.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Manual
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
Description and Operation
Manual HVAC Description and Operation HVAC - Manual
Electrical Information Reference
* Circuit Testing 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 References for scan tool information
Circuit/System Verification
1. Verify that DTC B048D 01 or B048D 06 is not set.
• If DTC B048D is set
Refer to Electrical Auxiliary Heater Control Circuit Malfunction.
• If DTC B048D is not set
2. Verify that DTC B048E 00 is not set.
• If DTC B048E is set
Refer to Electrical Auxiliary Heater Signal Circuit Malfunction.
• If DTC B048E is not set
3. All OK.
Circuit/System Testing
Electrical Auxiliary Heater Control Circuit Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module and the X1 harness connector at the E40 Electrical Auxiliary Heater, ignition ON.
2. Verify that a test lamp illuminates between the ignition circuit terminal 2 X1 at the E40 Electrical Auxiliary Heater harness connector and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the E40 Electrical Auxiliary Heater.
• If the test lamp illuminates
3. Test for less than 0.3 V between the control circuit terminal 7 X2 at the K33 HVAC Control Module harness connector and ground.
• If greater than 0.3 V
Repair the short to voltage on the circuit.
• If less than 0.3 V
4. Ignition OFF.
5. Test for infinite resistance between the control circuit terminal 7 X2 at the K33 HVAC Control Module harness connector and ground.
• If less than infinite resistance
Repair the short to ground on the circuit.
• If infinite resistance
6. Test for less than 5 ohms between the K33 HVAC Control Module control circuit terminal 7 X2 and control circuit terminal 1 X1 at the E40 Electrical Auxiliary Heater harness connector.
• If 5 ohms or greater
Repair the open/high resistance in the circuit.
• If less than 5 ohms
7. Replace the E40 Electrical Auxiliary Heater and verify the DTC does not reset.
• If DTC resets
Replace the K33 HVAC Control Module.
• If DTC does not reset
8. All OK.
Electrical Auxiliary Heater Signal Circuit Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module and the harness connectors at the E40 Electrical Auxiliary Heater, ignition ON.
2. Verify that a test lamp illuminates between the B+ circuit terminal 1 X2 at the E40 Electrical Auxiliary Heater harness connector and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the E40 Electrical Auxiliary Heater.
• If the test lamp illuminates
3. Verify that a test lamp illuminates between the B+ circuit terminal 1 X2 and ground circuit terminal 1 X3.
• If the test lamp does not illuminate
Repair the open/high resistance in the circuit.
• If the test lamp illuminates
4. Verify that a test lamp illuminates between the ignition circuit terminal 2 X1 and ground circuit terminal 1 X3.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the E40 Electrical Auxiliary Heater.
• If the test lamp illuminates
5. Test for less than 0.3 V between the signal circuit terminal 5 X2 at the K33 HVAC Control Module harness connector and ground.
• If greater than 0.3 V
Repair the short to voltage on the circuit.
• If less than 0.3 V
6. Ignition OFF.
7. Test for infinite resistance between the signal circuit terminal 5 X2 at the K33 HVAC Control Module harness connector and ground.
• If less than infinite resistance
Repair the short to ground on the circuit.
• If infinite resistance
8. Test for less than 5 ohms between the K33 HVAC Control Module signal circuit terminal 5 X2 and signal circuit terminal 4 X1 at the E40 Electrical Auxiliary Heater harness connector.
• If 5 ohms or greater
Repair the open/high resistance in the circuit.
• If less than 5 ohms
9. Replace the E40 Electrical Auxiliary Heater and verify the DTC does not reset.
• If the DTC resets
Replace the K33 HVAC Control Module.
• If the DTC does not reset
10. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Auxiliary Heater Core Replacement Auxiliary Heater Core Replacement
* Control Module References Control Module References for HVAC control module replacement, programming and setup