Introduction
The B1814 diagnostic trouble code (DTC) indicates a fault within the rear wiper motor down relay coil circuit. This circuit is critical for the proper operation of the rear windshield wiper system, specifically controlling the relay that allows the wiper motor to return to its parked, or "down," position. When this circuit malfunctions, the rear wiper may not function correctly, potentially affecting visibility and driving safety, especially in inclement weather. Addressing this issue promptly is essential to ensure the rear wiper system operates as intended.
Comprehensive Information Table
| Topic | Description | Possible Causes |
|---|---|---|
| B1814 Code Definition | Indicates a malfunction in the rear wiper motor down relay coil circuit. This code signifies that the vehicle's computer (PCM/BCM) has detected an open or short circuit within this specific part of the rear wiper system. | Open circuit in the wiring, short to ground, short to voltage, faulty rear wiper motor down relay, faulty BCM (Body Control Module), corrosion in connectors, faulty wiper motor itself (rarely). |
| Rear Wiper Motor Down Relay Function | This relay controls the power supply to the rear wiper motor, specifically the circuit that ensures the wiper returns to its parked position when switched off. It receives a signal from the BCM and controls the flow of electricity to the motor's park circuit. | Relay failure (coil open or shorted), control circuit failure from the BCM, wiring harness damage affecting relay control. |
| Symptoms of B1814 | Rear wiper not parking correctly, rear wiper not functioning at all, intermittent rear wiper operation, rear wiper stopping mid-sweep, battery drain (if the relay is stuck on), BCM may set other related DTCs. | Faulty rear wiper motor, wiring issues, faulty relay, BCM issues. |
| Common Wiring Locations | The wiring for the rear wiper motor and relay typically runs through the vehicle's body harness, often along the roof or floor, and connects to the rear hatch or liftgate. The relay is often located in a fuse box, either under the hood or inside the vehicle. | Wiring damage due to chafing, corrosion at connectors near the rear hatch hinges, damage from aftermarket accessory installation. |
| Testing the Relay Coil | Use a multimeter to check the resistance of the relay coil. A normal coil should have a measurable resistance (typically between 50-150 ohms). An open circuit indicates a faulty coil. Also, check for voltage at the relay control circuit when the wiper is switched off. | Multimeter failure, incorrect testing procedure, misunderstanding wiring diagrams. |
| BCM Involvement | The Body Control Module (BCM) controls many of the vehicle's body functions, including the rear wiper. It sends the signal to activate and deactivate the rear wiper motor down relay. A faulty BCM can cause incorrect signals, leading to the B1814 code. | Internal BCM failure, corrupted BCM software, wiring issues between the BCM and the relay. |
| Fuse and Ground Checks | Always check the fuses associated with the rear wiper system. A blown fuse can indicate a short circuit. Verify that the ground connections for the rear wiper motor and BCM are clean and secure. Poor grounds can cause erratic electrical behavior. | Blown fuse due to a short circuit, corroded ground connection, loose ground connection. |
| Diagnostic Tools Needed | Multimeter, wiring diagram for the vehicle's rear wiper system, scan tool capable of reading and clearing DTCs, test light (optional). | Lack of proper tools, inability to interpret wiring diagrams, unfamiliarity with using a multimeter. |
| Repair Procedures | 1. Visually inspect wiring and connectors. 2. Test the relay coil resistance. 3. Check for voltage at the relay control circuit. 4. Test the rear wiper motor. 5. Inspect and clean ground connections. 6. If all else fails, suspect the BCM. | Improper wiring repair, incorrect component replacement, failure to properly diagnose the root cause. |
| Related DTCs | Depending on the vehicle make and model, other DTCs related to the rear wiper system may be present, such as codes for the rear wiper motor itself, the wiper switch, or other BCM-related issues. These codes can help narrow down the source of the problem. | Misinterpreting related DTCs, focusing on the wrong code, failing to address all relevant issues. |
| Potential for Intermittency | The B1814 code, and the associated rear wiper malfunctions, can be intermittent. This means the problem may only occur under certain conditions (e.g., when the vehicle is cold, after driving for a long time, or when the rear hatch is opened/closed). Intermittent problems can be challenging to diagnose. | Vibration, temperature changes, moisture ingress. |
| Component Location Diagrams | Consult the vehicle's service manual or online repair databases for component location diagrams. These diagrams show the physical location of the rear wiper motor, relay, BCM, and associated wiring. Knowing the location of these components is essential for efficient troubleshooting. | Lack of access to service information, difficulty interpreting diagrams. |
| Safety Precautions | Always disconnect the negative battery terminal before working on the electrical system. Be careful when working around moving parts, such as the rear wiper motor. Avoid short-circuiting any circuits. Wear appropriate safety glasses and gloves. | Failure to disconnect the battery, accidental short circuits, injury from moving parts. |
| Preventative Maintenance | Regularly inspect the rear wiper blade for wear and tear. Replace the blade as needed. Keep the rear window clean to reduce the load on the wiper motor. Inspect the wiring and connectors for corrosion. | Neglecting regular maintenance, failing to address minor issues before they become major problems. |
| Aftermarket Accessories | Aftermarket accessories, such as trailer wiring or backup cameras, can sometimes interfere with the rear wiper system. If the B1814 code appeared after installing an aftermarket accessory, disconnect the accessory to see if the problem goes away. | Improper installation of aftermarket accessories, incorrect wiring connections. |
| Vehicle-Specific Information | The exact wiring diagrams, component locations, and troubleshooting procedures for the rear wiper system can vary significantly depending on the vehicle make, model, and year. Always consult the vehicle's service manual or a reputable online repair database for vehicle-specific information. | Using generic information instead of vehicle-specific data, failing to account for variations between different models. |
Detailed Explanations
B1814 Code Definition: The B1814 code, as previously stated, pinpoints a specific issue within the rear wiper system: a fault in the down relay coil circuit. This means the electrical circuit that controls the relay responsible for parking the rear wiper blade in its resting position is experiencing an irregularity, either an open circuit (a break in the wire) or a short circuit (an unintended connection to ground or another voltage source).
Rear Wiper Motor Down Relay Function: The rear wiper motor down relay is a crucial component. It acts as an electrical switch, controlled by the BCM. When the wiper is turned off, the BCM sends a signal to the relay, activating it. This allows power to flow to a specific circuit within the wiper motor, which drives the wiper blade back to its designated "parked" position at the bottom of the rear window. This ensures the wiper doesn't obstruct the driver's view.
Symptoms of B1814: The most obvious symptom is a rear wiper that doesn't park correctly. It might stop mid-sweep, leave the wiper blade in an awkward position, or not function at all. In some cases, the wiper might work intermittently. A less obvious symptom could be a slow battery drain if the relay is stuck in the "on" position, constantly drawing power. The BCM might also set other related DTCs, offering further clues to the problem.
Common Wiring Locations: The wiring for the rear wiper system is typically routed through the vehicle's body harness. This harness often runs along the roof or floor, eventually reaching the rear hatch or liftgate where the wiper motor is located. The relay itself is usually housed in a fuse box, which can be under the hood or inside the passenger compartment. The most vulnerable areas for wiring damage are near hinges (where wires can get pinched or broken) and connectors (where corrosion can occur).
Testing the Relay Coil: Testing the relay coil is a key diagnostic step. Using a multimeter set to measure resistance (Ohms), disconnect the relay and probe the two terminals of the coil. A healthy coil will have a measurable resistance, typically between 50 and 150 ohms. If the multimeter reads "OL" (overload) or a very high resistance, it indicates an open circuit within the coil, meaning the relay is faulty and needs replacement. Also, check the relay control circuit for voltage when the wiper is switched off. You should see voltage briefly as the BCM signals the wiper to park.
BCM Involvement: The Body Control Module (BCM) is the brain behind many of the vehicle's body functions, including the rear wiper system. The BCM sends the signal to the rear wiper motor down relay, telling it when to activate and deactivate. If the BCM is malfunctioning, it might send incorrect or no signals to the relay, leading to the B1814 code and wiper malfunctions.
Fuse and Ground Checks: Always begin troubleshooting electrical problems by checking the relevant fuses. A blown fuse is a sign of a short circuit, which needs to be investigated. Also, verify that the ground connections for the rear wiper motor and the BCM are clean, tight, and free of corrosion. Poor grounds can cause erratic electrical behavior and contribute to the B1814 code.
Diagnostic Tools Needed: To effectively diagnose the B1814 code, you'll need a few essential tools. A multimeter is crucial for testing voltage, resistance, and continuity. A wiring diagram for the vehicle's rear wiper system is indispensable for understanding the circuit layout and identifying components. A scan tool capable of reading and clearing DTCs is also necessary. A test light can be helpful for quickly checking for power at various points in the circuit.
Repair Procedures: The repair process typically involves a step-by-step approach. Start by visually inspecting the wiring and connectors for any signs of damage or corrosion. Then, test the relay coil resistance. Check for voltage at the relay control circuit. Test the rear wiper motor itself to rule out any internal motor issues. Inspect and clean all ground connections. If all these steps fail to identify the problem, the BCM might be the culprit.
Related DTCs: Pay attention to any other DTCs related to the rear wiper system. These might include codes for the rear wiper motor, the wiper switch, or other BCM-related issues. These codes can provide valuable clues and help narrow down the source of the problem. For example, a code indicating a short circuit in the wiper motor circuit could point to a wiring issue near the motor.
Potential for Intermittency: The B1814 code and the associated wiper malfunctions can be intermittent, meaning they come and go. This can make diagnosis more challenging. The problem might only occur under certain conditions, such as when the vehicle is cold, after driving for a long time, or when the rear hatch is opened or closed. Intermittent problems are often caused by loose connections, chafed wires, or temperature-sensitive components.
Component Location Diagrams: Finding the components you need to test and inspect is crucial. Consult the vehicle's service manual or online repair databases for component location diagrams. These diagrams show the physical location of the rear wiper motor, relay, BCM, and associated wiring. Knowing where these components are located will save you time and frustration.
Safety Precautions: Always prioritize safety when working on electrical systems. Disconnect the negative battery terminal before starting any work. Be careful when working around moving parts, such as the rear wiper motor. Avoid short-circuiting any circuits. Wear appropriate safety glasses and gloves to protect yourself.
Preventative Maintenance: Regular maintenance can help prevent the B1814 code and other rear wiper problems. Inspect the rear wiper blade regularly and replace it when it's worn. Keep the rear window clean to reduce the load on the wiper motor. Inspect the wiring and connectors for corrosion and address any issues promptly.
Aftermarket Accessories: Aftermarket accessories, such as trailer wiring or backup cameras, can sometimes interfere with the rear wiper system. If the B1814 code appeared after installing an aftermarket accessory, disconnect the accessory to see if the problem goes away. Improperly installed accessories can cause electrical interference or damage the vehicle's wiring.
Vehicle-Specific Information: The exact wiring diagrams, component locations, and troubleshooting procedures for the rear wiper system can vary significantly depending on the vehicle make, model, and year. Always consult the vehicle's service manual or a reputable online repair database for vehicle-specific information.
Frequently Asked Questions
What does the B1814 code mean? It indicates a malfunction in the rear wiper motor down relay coil circuit, meaning there's a problem with the electrical circuit that controls the relay responsible for parking the rear wiper.
What are the symptoms of a B1814 code? The most common symptom is a rear wiper that doesn't park correctly, but it can also include intermittent operation or complete failure.
How do I test the rear wiper motor down relay? Use a multimeter to check the resistance of the relay coil; a healthy coil should have a measurable resistance (typically 50-150 ohms).
Can a bad BCM cause a B1814 code? Yes, a faulty BCM can send incorrect signals to the relay, leading to the B1814 code.
Where is the rear wiper motor down relay located? It's usually located in a fuse box, either under the hood or inside the vehicle. Consult your vehicle's service manual for the exact location.
Is it safe to drive with a B1814 code? While not immediately dangerous, a malfunctioning rear wiper can impair visibility, especially in bad weather, so it should be addressed promptly.
Conclusion
The B1814 code signifies a problem with the rear wiper motor down relay coil circuit, which can lead to various rear wiper malfunctions. Thorough diagnostics, including wiring inspections, relay testing, and BCM evaluation, are crucial for accurate diagnosis and effective repair.