B3844

DTC B3844 (with HP7)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptor
DTC B3844
- Heater Core Pump Circuit

Diagnostic Fault Information





Circuit/System Description

The primary purpose of the heater core coolant pump is to circulate engine coolant through the HVAC heater core when heat is required in the cabin for comfort. This normally happens when the vehicle is in an Auto Stop and the mechanical pump is not spinning. If the HVAC control module has determined heat is needed for the cabin, this pump is turned on once the engine is shut off so the customer does not notice a change in heater duct discharge temperatures. The starter generator control module controls the auxiliary coolant pump.

Conditions for Running the DTC

* The ignition is ON.
* Ignition voltage is between 9-16 volts.
* The HVAC module is ON.

Conditions for Setting the DTC

Control circuit over current

Action Taken When the DTC Sets

Set heater core pump validity to invalid.

Conditions for Clearing the DTC

* Over current fault removed.
* Clears 30 seconds after cycle wake up signal.
* Open fault removed.
* Normal range for 3.5 seconds.

Reference Information
Schematic Reference

HVAC Schematics (HVAC - Automatic)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Air Delivery Description and Operation (Air Delivery Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Ignition ON, command the heater core pump ON and OFF with a scan tool.
2. Observe the operation of heater core pump.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the heater core coolant pump.
2. Verify that a test lamp illuminates between the B+ circuit terminal A and ground.

• If the test lamp does not light, test the B+ circuit for a short to ground, open or high resistance. If the circuit tests normal, replace the coolant heater pump

3. Ignition ON, verify that a test lamp illuminates between the control circuit terminal B and the ignition voltage terminal A while commanding the pump ON and OFF with a scan tool.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the Starter Generator Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning) for Starter Generator Control Module replacement, setup, and programming
* Generator Control Module Coolant Pump Replacement (Generator Control Module Coolant Pump Replacement)