Introduction
The B1815 diagnostic trouble code (DTC) indicates an issue within the electrical circuit controlling the rear windshield wiper motor's down relay. This relay is crucial for parking the wiper blade in its designated "down" or resting position when it's not in use. A fault in this circuit prevents the relay from energizing or de-energizing correctly, potentially leading to the rear wiper failing to park properly, remaining active when it shouldn't, or not functioning at all. Understanding the cause and troubleshooting this code is essential for maintaining safe and optimal vehicle operation.
Comprehensive Table: B1815 Wiper Rear Motor Down Relay Coil Circuit Open
| Topic | Description | Possible Causes |
|---|---|---|
| Rear Wiper System Overview | The rear wiper system consists of the wiper motor, linkage, wiper blade, control switch, wiring harness, fuse, relay (in this case, the "down" relay), and the vehicle's body control module (BCM) or equivalent control unit. The system is designed to clear the rear windshield for improved visibility in inclement weather. The "down" relay specifically ensures the wiper parks correctly when switched off. | N/A |
| B1815 Code Definition | B1815 signifies a fault in the circuit that energizes the coil of the rear wiper motor's "down" relay. This means the vehicle's computer (typically the BCM) is detecting an open circuit condition in the relay coil circuit, preventing the relay from functioning as intended. This "open circuit" prevents the relay from being activated, or deactivated, preventing the wiper motor from going to the proper position when switched off. | N/A |
| "Down" Relay Function | The "down" relay, specifically for the rear wiper, is responsible for ensuring the wiper blade returns to its parked or "down" position when the wiper switch is turned off. It does this by completing a circuit that allows the wiper motor to continue running briefly until a designated parking switch within the motor assembly is triggered, signaling that the wiper has reached the correct position. This is often achieved by using a dedicated winding within the wiper motor. | N/A |
| Symptoms of B1815 | Common symptoms include the rear wiper failing to park in the correct position (stopping mid-window), the rear wiper remaining active even after being switched off, the rear wiper not functioning at all, a warning light on the dashboard (if the BCM is programmed to trigger one), and potentially a clicking sound from the relay area, indicating a faulty relay attempting to engage. | N/A |
| Open Circuit Location | The "open circuit" can exist at various points within the circuit, including the wiring between the BCM (or equivalent control unit) and the relay, within the relay coil itself, in the connector to the relay, or in the ground circuit for the relay. It's crucial to identify the exact location to effectively diagnose and repair the issue. A break in the wire, a corroded connector, or a faulty relay are all potential culprits. | Broken wiring, corroded connectors, faulty relay, damaged BCM/control unit. |
| Testing the Relay | Testing the relay involves checking its resistance and continuity. Use a multimeter to measure the resistance across the relay coil terminals. A significantly high or infinite resistance indicates an open circuit within the coil. Also, check for continuity between the relay's power and ground terminals when the relay is activated (manually or with a scan tool). If there is no continuity, the relay is not functioning correctly. Refer to the vehicle's wiring diagram for specific pin locations and expected resistance values. | Faulty relay coil. |
| Wiring Harness Inspection | A thorough visual inspection of the wiring harness is crucial. Look for any signs of damage, such as frayed wires, cuts, abrasions, or corrosion. Pay close attention to areas where the harness is routed near sharp edges or moving parts. Use a multimeter to perform continuity tests on the wiring between the BCM (or equivalent control unit), the relay, and ground. Check for shorts to ground or voltage. Refer to the vehicle's wiring diagram to identify the correct wire colors and pin locations. | Damaged wiring, short circuits, open circuits, corrosion. |
| Connector Inspection | Inspect all connectors associated with the rear wiper system, including those at the BCM (or equivalent control unit), the relay, and the wiper motor. Look for signs of corrosion, loose pins, or damage to the connector housing. Clean corroded connectors with electrical contact cleaner. Ensure the connectors are properly seated and locked in place. Use dielectric grease to protect the connectors from future corrosion. | Corroded connectors, loose pins, damaged connectors. |
| BCM (or equivalent) Testing | While less common, the BCM (or equivalent control unit) could be the source of the problem. However, rule out all other possibilities first. Using a scan tool, check the BCM's output signals to the rear wiper relay circuit. If the BCM is not sending the correct signal, it may need to be reprogrammed or replaced. This usually requires specialized diagnostic equipment and expertise. Before replacing the BCM, verify the power and ground connections to the BCM are good. | Faulty BCM output, programming error. |
| Fuse and Ground Checks | Always start with the basics. Check the fuse for the rear wiper system. A blown fuse indicates a short circuit somewhere in the system. Replace the fuse with one of the correct amperage rating. Check the ground connections for the rear wiper system. Ensure the ground connections are clean, tight, and free from corrosion. A poor ground connection can cause a variety of electrical problems. | Blown fuse, poor ground connection. |
| Scan Tool Diagnostics | Use a scan tool to read and clear DTCs. Monitor the rear wiper system's parameters in real-time to identify any anomalies. Some scan tools can also activate and deactivate the rear wiper relay to test its functionality. This can help pinpoint the source of the problem. Refer to the vehicle's service manual for specific diagnostic procedures. | N/A |
| Repair Procedures | Repair procedures will vary depending on the identified cause. Broken wires should be repaired using proper splicing techniques. Corroded connectors should be cleaned or replaced. Faulty relays should be replaced with new ones. If the BCM (or equivalent control unit) is faulty, it may need to be reprogrammed or replaced. Always consult the vehicle's service manual for specific repair procedures. | N/A |
| Tools Required | Multimeter, wiring diagrams, scan tool, electrical contact cleaner, dielectric grease, wire stripper, crimping tool, soldering iron (optional), fuse puller, socket set, wrench set. | N/A |
| Safety Precautions | Always disconnect the negative battery cable before working on the electrical system. Wear safety glasses to protect your eyes. Use caution when working with electrical tools. Refer to the vehicle's service manual for specific safety precautions. | N/A |
| Related DTCs | Other DTCs related to the rear wiper system include those related to the wiper motor itself, the wiper switch, or other components of the system. Addressing these codes may be necessary to resolve the B1815 code. Common codes include those for motor malfunction, switch failure, or general circuit issues. | N/A |
| Importance of Wiring Diagrams | Wiring diagrams are essential for troubleshooting electrical problems. They provide a detailed map of the electrical circuits, showing the location of components, wire colors, and pin locations. Use the wiring diagram specific to your vehicle's year, make, and model. These diagrams are typically found in the vehicle's service manual or online databases. | N/A |
Detailed Explanations
Rear Wiper System Overview: The rear wiper system is designed to clear the rear windshield, improving visibility. It includes the motor, linkage, blade, switch, wiring, fuse, and relay.
B1815 Code Definition: B1815 indicates an open circuit in the rear wiper's "down" relay coil circuit. The BCM detects this open, preventing the relay's correct operation.
"Down" Relay Function: This relay ensures the wiper parks in its resting position by completing a circuit that allows the motor to briefly continue operation until the parking switch is triggered.
Symptoms of B1815: Symptoms include the wiper not parking correctly, remaining active when off, not functioning at all, a dashboard warning light, or a clicking sound from the relay.
Open Circuit Location: The open circuit can be in the wiring, relay coil, connector, or ground circuit. Identifying the specific location is crucial for repair.
Testing the Relay: Use a multimeter to check the relay's resistance and continuity. High resistance indicates an open coil. Absence of continuity when activated signals a faulty relay.
Wiring Harness Inspection: Inspect the wiring for damage, such as frayed wires or corrosion. Perform continuity tests to check for shorts or open circuits.
Connector Inspection: Check connectors for corrosion, loose pins, or damage. Clean corroded connectors and ensure they are properly seated.
BCM (or equivalent) Testing: While less common, the BCM may be the problem. Check its output signals to the relay circuit with a scan tool after ruling out other causes.
Fuse and Ground Checks: Start by checking the fuse for the rear wiper system. Also, ensure the ground connections are clean, tight, and free from corrosion.
Scan Tool Diagnostics: Use a scan tool to read and clear DTCs and monitor system parameters in real-time.
Repair Procedures: Repair procedures depend on the identified cause. Repair broken wires, clean or replace corroded connectors, and replace faulty relays.
Tools Required: A multimeter, wiring diagrams, scan tool, electrical contact cleaner, dielectric grease, wire stripper, crimping tool, and socket/wrench sets are needed.
Safety Precautions: Always disconnect the negative battery cable before working on the electrical system.
Related DTCs: Other codes related to the wiper system may need to be addressed to resolve the B1815 code.
Importance of Wiring Diagrams: Wiring diagrams are essential for understanding the circuit and identifying components and wire locations.
Frequently Asked Questions
What does B1815 mean? B1815 indicates an open circuit in the rear wiper motor's "down" relay coil circuit, preventing the relay from functioning correctly.
What are the symptoms of a B1815 code? The rear wiper may not park correctly, remain active when off, or not function at all.
How do I test the rear wiper relay? Use a multimeter to check the relay's resistance and continuity. High resistance indicates an open coil.
Can a bad fuse cause a B1815 code? While a blown fuse typically indicates a short circuit, it's always good practice to check the fuse for the rear wiper system.
Is it safe to drive with a B1815 code? It's generally safe, but the rear wiper may not function correctly, affecting rear visibility in bad weather.
Conclusion
The B1815 code indicates a problem within the rear wiper motor's "down" relay coil circuit. Thorough diagnosis, including checking the relay, wiring, connectors, and ground connections, is necessary to pinpoint the issue and restore proper operation of the rear wiper system.