B3718 - Front Wiper Relay Drive Circuit High (BCM)

Introduction:

The B3718 diagnostic trouble code (DTC) indicates a fault within the front wiper relay drive circuit, specifically a "High" voltage condition, as detected by the Body Control Module (BCM). This means the BCM is sensing a higher-than-expected voltage on the circuit it uses to control the front wiper relay. Addressing this issue promptly is crucial to ensure the proper functioning of your vehicle's windshield wipers, a vital safety feature during inclement weather.

Table: B3718 Diagnostic Information

Detailed Explanations:

Code Definition: The B3718 code signifies that the Body Control Module (BCM) has detected an abnormally high voltage level in the circuit it uses to control the front wiper relay. This relay is responsible for supplying power to the wiper motor. The BCM monitors this circuit to ensure proper operation.

Affected System: The primary system affected is the front windshield wiper system. This includes the wiper motor, wiper arms, wiper blades, the wiper relay, the wiring harness connecting these components, and the Body Control Module (BCM) which controls the system.

Symptoms: Several symptoms can indicate a B3718 code. These include:

• Erratic or Non-Functional Wipers: The wipers may operate intermittently, not at all, or at the wrong speed.
• Constant Wiper Operation: The wipers may run continuously, even when the wiper switch is turned off.
• No Response to Switch Inputs: The wipers may not respond to any changes in the wiper switch position.
• BCM Failsafe Mode: In some cases, the BCM might enter a failsafe mode, potentially affecting other vehicle systems. This is a protective measure to prevent further damage.

Possible Causes: The B3718 code can arise from several potential issues:

• Short to Voltage: A wire in the wiper relay drive circuit could be shorted to a positive voltage source, such as another circuit or the vehicle's battery. This is a common cause.
• Faulty Wiper Relay: An internal failure within the wiper relay can cause it to send high voltage feedback to the BCM.
• BCM Failure: Although less common, an internal malfunction within the BCM itself can affect the wiper relay drive circuit.
• Wiring Issues: Damaged, corroded, or loose wiring connections can disrupt the circuit's voltage levels.
• Open Circuit: A broken wire or loose connection in the ground path of the circuit can cause a higher voltage reading at the BCM.
• Incorrect Wiper Motor: Replacing the wiper motor with an incorrect model can cause an overdraw of current or voltage feedback issue.
• Aftermarket Accessories: Improperly installed aftermarket accessories can interfere with the wiper system circuit, potentially causing voltage fluctuations.

Diagnostic Steps: Diagnosing a B3718 code requires a systematic approach:

1. Verify the DTC: Use a scan tool to confirm the presence of the B3718 code and check for any other related codes.
2. Inspect Wiring and Connectors: Carefully examine the wiring harness and connectors associated with the wiper motor, wiper relay, and BCM for any signs of damage, corrosion, or loose connections. Pay close attention to areas where the wiring harness may be rubbing against metal components.
3. Test the Wiper Relay: Use a multimeter to test the wiper relay according to the vehicle's service manual specifications. You can also try swapping the relay with a known good relay to see if the problem is resolved.
4. Check BCM Output Voltage: With the wiper switch in different positions, use a multimeter to check the voltage at the BCM output for the wiper relay drive circuit. Compare the readings to the values specified in the service manual.
5. Inspect Wiper Motor: Examine the wiper motor and its connections for any signs of damage or corrosion. Test the motor's operation by applying power directly to it.
6. Examine BCM: Visually inspect the BCM for any signs of physical damage, corrosion, or water intrusion.
7. Consult Service Manual: Refer to the vehicle's service manual for specific diagnostic procedures, wiring diagrams, and component locations.

Common Repair Solutions: The appropriate repair solution depends on the underlying cause of the B3718 code:

• Repairing or Replacing Wiring: Repairing damaged wires or replacing sections of the wiring harness is often necessary to address short circuits or open circuits.
• Replacing the Wiper Relay: If the wiper relay is found to be faulty, replacing it with a new relay is the most common solution.
• Replacing the Wiper Motor: If the wiper motor is damaged or malfunctioning, replacing it may be necessary.
• Replacing the BCM: If the BCM is determined to be the cause of the problem, it will need to be replaced and programmed to the vehicle. This is typically performed by a qualified technician.
• Cleaning or Tightening Connections: Cleaning corroded connections and tightening loose connections can often resolve voltage issues.

Related DTCs: The B3718 code may be accompanied by other related DTCs, such as:

• B3717 - Front Wiper Relay Drive Circuit Low (BCM): This code indicates a low voltage condition in the wiper relay drive circuit.
• B3700-B3799 (other BCM related codes): These codes could indicate other issues within the Body Control Module that may be related to the wiper system malfunction.

Component Location:

• Wiper Relay: The wiper relay is typically located in the under-hood fuse box or relay panel. Refer to the vehicle's owner's manual or service manual for its specific location.
• Wiper Motor: The wiper motor is located near the base of the windshield, usually under a cowl panel.
• BCM: The Body Control Module (BCM) is usually found under the dashboard, often near the steering column or in the center console.

Tools Required:

• Scan Tool: A scan tool is necessary to read and clear diagnostic trouble codes.
• Multimeter: A multimeter is essential for testing voltage, resistance, and continuity in electrical circuits.
• Wiring Diagram: A wiring diagram is crucial for understanding the wiper system's circuit layout and identifying potential fault locations.
• Basic Hand Tools: Basic hand tools, such as screwdrivers, pliers, and sockets, are needed for accessing and disconnecting components.

Frequently Asked Questions:

• What does the B3718 code mean? The B3718 code means the Body Control Module (BCM) has detected a high voltage condition in the front wiper relay drive circuit. This indicates a potential problem with the wiring, relay, or BCM itself.

• Can I fix the B3718 code myself? Depending on your mechanical skills and access to tools, you may be able to diagnose and repair some causes of the B3718 code, such as repairing damaged wiring or replacing the wiper relay. However, BCM replacement and programming should be left to a professional.

• How much does it cost to fix the B3718 code? The cost to fix the B3718 code can vary depending on the cause. Replacing a faulty relay might cost $50-$100, while replacing the BCM can cost several hundred dollars, including programming.

• Is it safe to drive with the B3718 code? Driving with a malfunctioning wiper system can be dangerous, especially in inclement weather. It is recommended to address the issue as soon as possible.

• Can a dead battery cause a B3718 code? While a weak or dead battery can sometimes cause various electrical issues, it's less likely to directly cause a B3718 code. However, it's always a good idea to ensure your battery is in good condition during troubleshooting.

Conclusion:

The B3718 DTC points to a high voltage issue within the front wiper relay drive circuit, impacting the functionality of your windshield wipers. A systematic approach to diagnosis, starting with wiring inspection and component testing, is crucial for identifying the root cause and implementing the appropriate repair. Addressing this issue promptly ensures safe driving conditions, particularly during adverse weather.