B3874

DTC B3874 (V8) (5.3L)

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 B3874 00
- Wiper Low Speed Relay Circuit

Diagnostic Fault Information





Circuit/System Description

The body control module (BCM) controls and monitors the state of the wiper relay control circuit. When the windshield wiper switch is placed in to a low speed setting, a signal is applied to the BCM. The BCM then applies battery positive voltage to the coil side of the WIPER PCB Relay through the wiper relay control circuit. This energizes the relay, applying battery positive voltage from the WPR fuse through the switched side of the relay to the windshield wiper motor. Ground is applied at all times to the coil side of the wiper relay and the windshield wiper motor form G201.

Conditions for Running the DTC

* The ignition is in the ON position.
* The ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

* The BCM detects an short to battery positive voltage in the wiper high speed relay control circuit for over 1 second.
* The BCM detects an open or a short to ground in the wiper high speed relay control circuit for over 1 second.

Action Taken When the DTC Sets

The BCM will not activate the output.

Conditions for Clearing the DTC

* The DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Reference Information
Schematic Reference

Wiper/Washer Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Wiper/Washer System Description and Operation (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)

Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal A1 and battery voltage.
3. Command the Wiper PCB Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the body control module.

• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the body control module.

4. If all circuits test normal, test or replace the underhood fuse block.

Repair Instructions

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

* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming