GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Uplander Ext. 🢒 Brakes 🢒 Park Brake 🢒 DTC B1433

Circuit Description

The body control module (BCM) controls the HVAC blower motors through the RUN relay circuit. When the ignition switch is in either the ACC or the ON position, the BCM provides battery negative voltage to the RUN relay control circuit. When the RUN relay is energized, it supplies B+ to the HVAC blower motor switches.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1433 Ignition-Switched Power Relay 2 Circuit

Conditions for Running the DTC

The system voltage must be between 9-16 volts.

Conditions for Setting the DTC
    • The BCM detects a short to voltage in the RUN relay control circuit when the BCM is trying to energize the relay.
    • The BCM detects that the RUN relay control circuit is open.
    • The condition above must be present for more than 1 second.

Action Taken When the DTC Sets
    • The BCM stores DTC B1433 in memory.
    • The devices powered by the RUN supply voltage circuit will not operate.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Test Description

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

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

    2.

  2. This step tests for voltage at the coil side of the RUN relay.

    3.

  3. This step verifies that the BCM is providing ground to the RUN relay.

    4.

  4. This step tests the control circuit side of the RUN relay for faults.

    5.

  5. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Body Control System Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the RUN relay ON and OFF.

Does the RUN relay turn ON and OFF with each command?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Remove the RUN relay.
  3. Turn the engine ON, with the engine OFF.
  4. Test the control circuit at the RUN relay socket for voltage and ground as required by the schematic. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 4

4

  1. Connect a test lamp between the RUN relay control circuit of the RUN relay socket and the battery positive voltage circuit of the RUN relay.
  2. With a scan tool, command the RUN relay ON and OFF .

Does the test lamp turn ON and OFF?

Go to Step 6

Go to Step 5

5

Test the control circuit of the RUN relay from the body control module (BCM) for the following conditions:

    • A short to ground
    • A short to battery positive voltage
    • An open circuit

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

6

Inspect for poor connections and terminal damage at the RUN relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

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

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the non switched B+ circuit of the RUN relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

9

Replace the RUN relay.

Did you complete the replacement?

Go to Step 11

--

10

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 11

--

11
  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