B3874

DTC B3874 (V6)

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 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 relay through the wiper relay control circuit. This energizes the wiper relay, allowing battery positive voltage from the wiper/ws fuse through the switched side of the wiper 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) for scan tool information.

Circuit/System Verification

Ignition ON, wiper switch in the Low position. Verify the windshield wipers are cycling at the low speed.

Circuit/System Testing

1. Ignition OFF, disconnect the Wiper Relay.
2. Connect a test lamp between the control circuit terminal 85 and ground.
3. Ignition ON, command the Low speed wipers ON and OFF using the wiper switch. 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 Voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the WIPER Relay.

Component Testing

Relay Test
1. Ignition OFF, disconnect the WIPER Relay.
2. Test for 60-200 ohms between terminals G14 and E15.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* G15 and E15
* G15 and E14
* G15 and G14
* G14 and E14

• If not the specified value, replace the relay.

4. Test for less than 2 ohms between terminals G15 and F14.

• If greater than the specified range, replace the relay.

5. Install a 10A fused jumper wire between relay terminal G14 and 12 volts. Install a jumper wire between relay terminal E15 and ground. Test for less than 2 ohms between terminals G15 and E14.

• If greater than the specified range, replace the WIPER Relay.

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