DTC B3874 with RPO L26 or L32
Circuit 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B3874 Wiper Low Speed Relay Circuit
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 following conditions will cause the DTC to set:
| • | The BCM detects an short to battery positive voltage in the wiper relay control circuit for over 1 second. |
| • | The BCM detects a short to ground or an open in the wiper relay control circuit. |
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 without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections .
Step | Action | Yes | No | ||||
|---|---|---|---|---|---|---|---|
Schematic Reference: Wiper/Washer Schematics Connector End View Reference: Master Electrical Component List . | |||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||
2 |
Do the windshield wipers operate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||
3 |
Does the test lamp illuminate? | Go to Step 8 | Go to Step 4 | ||||
4 |
Does the test lamp illuminate? | Go to Step 5 | Go to Step 6 | ||||
5 |
Does the test lamp illuminate? | Go to Step 9 | Go to Step 7 | ||||
6 | Test for a poor connection, an open, or short to ground in the wiper relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 10 | ||||
7 | Test for a poor connection or an open in the ground circuit of the wiper relay. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 12 | Go to Step 11 | ||||
8 | Repair a short to battery positive voltage in the wiper relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair? | Go to Step 12 | -- | ||||
9 |
Does the DTC reset? | Go to Step 11 | Go to Step 12 | ||||
10 | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 12 | -- | ||||
11 | Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement . Did you complete the replacement? | Go to Step 12 | -- | ||||
12 |
Does the DTC reset? | Go to Step 2 | System OK | ||||
DTC B3874 with LS4
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC B3874 00: Wiper Low Speed Relay CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Windshield Wiper Motor Relay Coil Supply Voltage | B3874 | 2 | 6 | -- |
Windshield Wiper Switch High Signal | 6 | 4 | 1 | -- |
Windshield Wiper Switch Low Signal | 6 | 3 | 1 | -- |
Windshield Wiper Motor Park Switch Signal | 5 | 5 | -- | -- |
Windshield Wiper High Speed Relay Control | 7 | 4 | B3875 | -- |
Windshield Wiper Motor High Speed Control | 2 | 4 | -- | -- |
Windshield Wiper Motor Low Speed Control | 2 | 3 | -- | -- |
Wiper PCB Relay Ground | -- | 2 | -- | -- |
Windshield Wiper Motor Ground | -- | 2 | -- | -- |
Windshield Wiper Switch Ground | -- | 1 | -- | -- |
1. Wipers and Washers Inoperative All Modes 2. Wipers Inoperative All Modes and Washers Work 3. Delay or Low Speed Wipers Inoperative 4. High Speed Wipers Inoperative 5. Wipers Do Not Park 6. Wipers Always On 7. Wipers Operate at High Speed in the Low Speed Mode | ||||
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
Connector End View Reference
Wiper/Washer Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the C2 harness connector at the underhood fuse block.
- Connect a test lamp between the control circuit terminal A1 and battery voltage.
- Command the Wiper Motor Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the underhood fuse block.
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
