GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 DTC 🢒 DTC B3844

Circuit Description

The hybrid control module (HCM) controls the coolant pump operation by applying voltage to the coolant pump relay control circuit with an internal solid state device called a driver. When the HCM is commanding the relay ON, the voltage of the control circuit should be high, near 12 volts. When the HCM is commanding the relay OFF, the voltage potential of the control circuit should be low, near 0 volts.

The HCM monitors the relay control circuits for the following conditions:

    • Short to ground
    • Short to voltage
    • An open circuit

If the HCM detects an improper voltage level on the coolant pump control circuit driver circuit, then DTC B3844 will set and the driver will be disabled.

Conditions for Running the DTC
    • The ignition switch is in the RUN or CRANK position.
    • DTC B1422 is not set.
    • The ignition 0 voltage circuit input is within 8 to 16 volts.

Conditions for Setting the DTC

The HCM determines the state of the coolant pump relay control circuit is shorted to ground, open or shorted to power.

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Listen for an audible click when the auxiliary water pump relay operates. Command both the ON and OFF states. Repeat the commands as necessary.

    2.

  2. Tests for voltage at the coil side of the auxiliary water pump relay. The AUX HTR PUMP fuse supplies power to the coil side of the auxiliary water pump relay.

    3.

  3. Verifies that the HCM is providing ground to the auxiliary water pump relay.

    4.

  4. Tests if ground is constantly being applied to the auxiliary water pump relay.

Step

Action

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

1

Did you perform the Engine Cooling Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Cooling

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Auxiliary Coolant Pump Relay ON and OFF.

Does the auxiliary water pump relay turn ON and OFF with each command?

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the auxiliary water pump relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery positive voltage circuit of the auxiliary water pump relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 10

4
  1. Connect a test lamp between the control circuit of the auxiliary water pump relay and the battery positive voltage circuit of the auxiliary water pump relay.
  2. With a scan tool, command the Auxiliary Coolant Pump Relay ON and OFF .

Does the test lamp turn ON and OFF with each command?

Go to Step 8

Go to Step 5

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the control circuit of the auxiliary water pump relay for a short to voltage and an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the control circuit of the auxiliary water pump relay for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

Inspect for poor connections at the auxiliary water pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

9

Inspect for poor connections at the harness connector of the HCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Repair the battery positive voltage circuit of the auxiliary water pump relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the auxiliary water pump relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the set up procedure for the HCM .

Replace the HCM. Refer to Powertrain Control Interface Module Replacement in Engine Electrical.

Did you complete the replacement?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK