Introduction
The B1816 diagnostic trouble code (DTC) signals a specific electrical fault within the rear wiper system of a vehicle, specifically a short to battery voltage in the down relay coil circuit. This means the wire that controls the relay responsible for moving the rear wiper to its "down" or park position is inadvertently receiving power directly from the vehicle's battery. This can lead to the relay being constantly energized, potentially causing the rear wiper to malfunction, drain the battery, or even damage related components. Understanding the causes, symptoms, and diagnostic procedures for a B1816 code is crucial for effective troubleshooting and repair.
Table: B1816 Wiper Rear Motor Down Relay Coil Circuit Short to Battery
| Topic | Description | Possible Causes |
|---|---|---|
| B1816 DTC Definition | Indicates a short to battery voltage in the rear wiper motor down relay coil circuit. The control circuit for the relay that moves the wiper to the down/park position is receiving unintended power from the battery. | - Damaged wiring: Frayed, cracked, or melted insulation allowing the wire to contact a power source. - Shorted relay: Internal fault in the relay itself, causing it to be permanently energized. - Faulty connectors: Corroded or damaged connectors providing a path for unintended voltage. - Wiring harness rubbing: Wire harness rubbing against the vehicle chassis causing insulation wear and a short. - Aftermarket accessories: Improperly installed accessories interfering with the rear wiper circuit. |
| Symptoms | - Rear wiper constantly running or stuck in the "down" position. - Rear wiper not functioning at all. - Battery drain. - Burnt fuse related to the rear wiper circuit. - Unusual noises from the rear wiper motor or relay. - Rear wiper only works intermittently. - Rear wiper position is not properly parked. |
N/A |
| Diagnostic Steps | 1. Visual Inspection: Inspect wiring, connectors, and the relay for damage. 2. Check Fuses: Verify the fuse for the rear wiper motor is not blown. 3. Relay Test: Test the rear wiper down relay for proper function using a multimeter or relay tester. 4. Voltage Test: Measure voltage at the relay coil circuit to confirm the short to battery. 5. Continuity Test: Check the wiring for continuity to ground to rule out a short to ground in addition to the short to battery. 6. Wiring Diagram Review: Consult a wiring diagram to trace the circuit and identify potential short locations. 7. Component Isolation: Disconnect components in the circuit one at a time to isolate the short. 8. Scan Tool Data: Use a scan tool to monitor rear wiper motor and relay status. |
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| Possible Solutions | - Repair or replace damaged wiring. - Replace the faulty rear wiper down relay. - Clean or replace corroded connectors. - Secure the wiring harness to prevent rubbing. - Remove or properly install aftermarket accessories. - Replace the rear wiper motor (if the motor itself is causing the short). - Repair the Body Control Module (BCM) if it is the source of the problem (rare). |
N/A |
| Related Components | - Rear wiper motor: The motor that drives the rear wiper arm. - Rear wiper down relay: The relay that controls the movement of the wiper arm to the parked position. - Wiring harness: The bundle of wires connecting the various components of the rear wiper system. - Connectors: The electrical connectors that join the wires and components. - Fuses: Protective devices that prevent overcurrent in the circuit. - Body Control Module (BCM): The computer that controls various vehicle functions, including the rear wiper. |
N/A |
Detailed Explanations
B1816 DTC Definition: This code is vehicle-specific, and the "B" prefix indicates a body code. It precisely pinpointed a short to battery voltage within the control circuit for the rear wiper motor's down relay coil. This relay is specifically responsible for positioning the rear wiper in its parked or "down" position when the wiper is turned off. The "coil circuit" refers to the electromagnet within the relay that, when energized, closes the relay contacts and activates the wiper motor. The short to battery means the coil is receiving power it shouldn't, even when the wiper system is supposedly off.
Symptoms: The symptoms of a B1816 code can vary depending on the severity of the short and the design of the vehicle's rear wiper system. The most common symptom is the rear wiper constantly running or being stuck in the down position. This occurs because the relay is constantly energized. Other symptoms include a complete lack of rear wiper function, a noticeable battery drain (due to the constant power draw of the energized relay), a blown fuse related to the rear wiper circuit, unusual noises emanating from the rear wiper motor or relay, intermittent wiper operation, and the wiper not parking correctly.
Diagnostic Steps: Accurately diagnosing a B1816 code requires a methodical approach. Begin with a thorough visual inspection of the wiring, connectors, and relay associated with the rear wiper system, looking for any signs of damage like frayed wires, corroded connectors, or a burnt relay. Check the fuses related to the rear wiper motor to ensure they are intact. Next, test the rear wiper down relay using a multimeter or a dedicated relay tester to confirm it's functioning correctly. Measure the voltage at the relay coil circuit to verify the presence of the short to battery. Perform a continuity test to check for any shorts to ground as well, as multiple faults can sometimes exist. Consult a wiring diagram to understand the circuit layout and identify potential short locations. Isolate components by disconnecting them one at a time to pinpoint the exact source of the short. Finally, use a scan tool to monitor the rear wiper motor and relay status and retrieve any related data.
Possible Solutions: Once the cause of the B1816 code is identified, the appropriate solution can be implemented. This might involve repairing or replacing damaged wiring, replacing the faulty rear wiper down relay, cleaning or replacing corroded connectors, securing the wiring harness to prevent rubbing against the vehicle chassis, removing or properly installing aftermarket accessories that may be interfering with the circuit, replacing the rear wiper motor (if the motor itself is internally shorted and causing the problem), or, in rare cases, repairing the Body Control Module (BCM) if it is the root cause of the issue.
Related Components: The rear wiper system consists of several interconnected components. The rear wiper motor is the primary actuator responsible for moving the wiper arm. The rear wiper down relay specifically controls the movement of the wiper arm to the parked position. The wiring harness provides the electrical pathways connecting all the components. Connectors join the wires and components, ensuring proper electrical contact. Fuses protect the circuit from overcurrent damage. The Body Control Module (BCM) may control the rear wiper system in some vehicles, providing signals to the relay and monitoring its operation.
Frequently Asked Questions
What does a B1816 code mean? It indicates a short to battery voltage in the rear wiper motor down relay coil circuit, meaning the relay coil is receiving unintended power.
Can I drive my car with a B1816 code? While you can usually drive, it's not recommended. The constant power draw can drain the battery, and the malfunctioning wiper can be a safety hazard.
How do I fix a B1816 code? Diagnose the cause (damaged wiring, faulty relay, etc.) and then repair or replace the affected component.
Is a B1816 code serious? It can be, as it can lead to battery drain and a malfunctioning wiper, potentially affecting visibility.
Can a bad relay cause a B1816 code? Yes, a shorted relay is a common cause of this code, as it will be constantly energized.
Conclusion
The B1816 DTC points to a specific electrical fault in the rear wiper system, related to a short to battery voltage within the down relay coil circuit. Thorough diagnosis and repair are necessary to restore proper rear wiper function and prevent potential battery drain or further component damage.