For 1990-2009 cars

### 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 B3715 01: Front Wiper Relay Circuit Short to Battery
DTC B3715 02: Front Wiper Relay Circuit Short to Ground
DTC B3715 04: Front Wiper Relay Circuit Open Circuit
DTC B3875 01: Windshield Wiper High Speed Relay Circuit Short to Battery
DTC B3875 02: Windshield Wiper High Speed Relay Circuit Short to Ground
DTC B3875 04: Windshield Wiper High Speed Relay Circuit open Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Windshield Wiper High Speed Relay B+ | 1, 2 | 1, 2 | -- | --
Windshield Wiper Switch Low Signal | 1 | 1 | 1 | --
Windshield Wiper Switch High Signal | 4 | 2 | 2 | --
Windshield Wiper Motor Park Switch Signal | 3 | 3 | -- | --
Front Wiper Relay Control | B3715 02 | B3715 04 | B3715 01 | --
Windshield Wiper High Speed Relay Control | B3875 02 | B3875 04 | B3875 01 | --
Windshield Wiper High Speed Relay Control | 2 | 2 | 4 | --
Front Wiper Motor Low Speed Control | 1 | 1 | 4 | --
Windshield Wiper Switch Low Reference | -- | 1, 2 | 1, 2 | --
Windshield Wiper Motor Ground | -- | 1, 2, 3 | -- | --
Front Wiper Relay Ground | -- | 1 | -- | --
1. Delay or Low Speed Wipers Inoperative 2. High Speed Wipers Inoperative 3. Wipers Do Not Park 4. Wipers Always ON

### Circuit/System Description

The Body Control Module (BCM) controls the windshield wiper motor based on input from the windshield wiper/washer switch. The BCM monitors the wiper/washer switch through two separate signal circuits and a ground circuit. The windshield wiper switch high signal circuit is used to determine high speed wiper operation, the windshield wiper switch low signal is used to determine low speed, intermittent, and mist operation through the use of a resistor ladder, and windshield washer switch signal circuit is used to determine washer operation.

The BCM controls the windshield wiper motor through two output controls, controlling two relays which determine the desired wiper speed, high or low.

### Conditions for Running the DTC

• | The DTC runs only when a wiper output is actively being requested by the BCM.

• | The system voltage is between 9 V and 16 V.

### Conditions for Setting the DTC

• | A short to voltage is detected in the Front Wiper Relay control circuit or in the High Speed Relay control circuit.

• | A short to ground or an open/high resistance is detected in the Front Wiper Relay control circuit or in the High Speed Relay control circuit.

### Action Taken When the DTC Sets

The BCM will not activate the wiper output.

### Conditions for Clearing the DTC

• | A current DTC will clear when the condition for setting the fault is no longer seen.

• | A history DTC will clear after 50 consecutive ignition cycles without a fault present.

### Reference Information

#### Schematic Reference

Wiper/Washer Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Wiper/Washer System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for diagnostic tester information.

### Circuit/System Verification

Ignition ON, S80 Window Wiper/Washer Switch in LOW position. Verify the front wipers are cycling at the low speed.

Ignition ON, S80 Window Wiper/Washer Switch in the HIGH position. Verify the front wipers are cycling at the high speed.

### Circuit/System Testing

#### DTC B3715

1. Ignition OFF, disconnect the KR12B Windshield Wiper Relay.
2. Connect a test lamp between the control circuit terminal 86 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 K9 Body Control Module (BCM).

⇒ | If the test lamp is always OFF, test for a short to ground or an open/high resistance on the control circuit. If the circuit tests normal, replace the K9 Body Control Module (BCM).

4. If all circuits test normal, test or replace the KR12B Windshield Wiper Relay.

#### DTC B3875

1. Ignition OFF, disconnect the KR12C Windshield Wiper Speed Control Relay.
2. Connect a test lamp between the control circuit terminal 86 and B+.
3. Ignition ON, command the high speed wipers ON and OFF using the S78 Turn Signal/Multifunction 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 ground. If the circuit tests normal, replace the K9 Body Control Module (BCM).

⇒ | 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 K9 Body Control Module (BCM).

4. If all circuits test normal, test or replace the KR12C Windshield Wiper Speed Control Relay.

### Component Testing

#### DTC B3715

#### Relay Test

1. Ignition OFF, disconnect the KR12B Windshield Wiper Relay.
2. Test for 60-200 Ω between terminals 85 and 86.

⇒ | If the resistance is not within the specified range, replace the KR12B Windshield Wiper Relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the KR12B Windshield Wiper Relay.

4. Test for less than 5 Ω between terminals 30 and 87A.

⇒ | If greater than the specified value, replace the KR12B Windshield Wiper Relay.

5. Install a 10A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 Ω between terminals 30 and 87.

⇒ | If greater than the specified range, replace the KR12B Windshield Wiper Relay.

#### DTC B3875

#### Relay Test

1. Ignition OFF, disconnect the KR12C Windshield Wiper Speed Control Relay.
2. Test for 60-200 Ω between terminals 85 and 86.

⇒ | If the resistance is not within the specified range, replace the KR12C Windshield Wiper Speed Control Relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the KR12C Windshield Wiper Speed Control Relay.

4. Test for less than 5 Ω between terminals 30 and 87A.

⇒ | If greater than the specified value, replace the KR12C Windshield Wiper Speed Control Relay.

5. Install a 10A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 5 Ω between terminals 30 and 87.

⇒ | If greater than the specified value, replace the KR12C Windshield Wiper Speed Control Relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Control Module References for BCM replacement, setup, and programming.

• | Relay Replacement