GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 DTC 🢒 DTC B3874

Circuit Description

The body control module, (BCM) controls and monitors the state of the Wiper Relay control circuit. The wiper relay is used to control the low speed wiper function. The BCM supplies a negative voltage to the relay. The relay is supplied B+ from the WIPER/WS fuse. The voltage level from the BCM should be high while the relay is inactive. The voltage should be near ground when the BCM commands the relay ON.

Conditions for Running the DTC
    • The ignition is ON.
    • The ignition voltage is between 9-18.5 volts.

Conditions for Setting the DTC

The following conditions will cause the DTC to set:

    • The BCM detects an over current condition in the Wiper Relay control circuit for over 1 second.
    • The BCM does not detect the load of the wiper relay or the circuit is open.

Action Taken When the DTC Sets

The BCM will not activate the Wiper Relay.

Conditions for Clearing the DTC
    • This DTC will change from current to history once the ignition is turned OFF and the BCM is asleep.
    • A history DTC will clear after 100 ignition cycles if the condition is no longer present.

Step

Action

Yes

No

Schematic Reference: Wiper/Washer Schematics

Connector End View Reference: Wiper/Washer Connector End Views

1

Did you perform the Wiper/Washer Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Wiper/Washer

2
  1. Turn the ignition ON with the engine OFF.
  2. Select low speed wiper operation on the wiper switch.

Do the windshield wipers operate?

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

Go to Step 3

3
  1. Remove the Wiper Relay.
  2. Remove the harness connector from the BCM that contains the Wiper Relay control circuit.
  3. Test the Wiper Relay control circuit between the BCM harness connector and the wiper relay socket for a short to ground, short to voltage or an open circuit. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 4

4

With the Wiper Relay removed, test the B+ circuit using a test lamp at the wiper relay socket. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5
  1. Replace the Wiper Relay.
  2. Connect all disconnected connectors.
  3. Turn the ignition ON with the engine OFF.
  4. Operate the wipers in the low speed mode.
  5. Using a scan tool observer the DTC.

Is DTC B3874 still current?

Go to Step 6

Go to Step 7

6

Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.

Did you complete the action?

Go to Step 7

--

7
  1. Make sure all disconnected connectors are installed.
  2. Clear the DTC using the Tech 2.
  3. Operate the system to verify the repair.

Does the DTC reset?

Go to Step 1

System OK