B1684 Mirror Driver/Passenger Switch Circuit Open

Introduction:

The B1684 diagnostic trouble code (DTC) signals an open circuit within the driver or passenger side mirror switch circuit. This means the vehicle's computer (often the Body Control Module or BCM) isn't receiving the expected electrical signal from the mirror control switch, preventing proper operation of the power mirrors. Addressing this issue promptly is crucial for maintaining safe driving conditions, as functional mirrors are essential for visibility and maneuvering.

Table: B1684 Mirror Driver/Passenger Switch Circuit Open - Diagnostic Information

Detailed Explanations:

Code Definition: The B1684 code specifically indicates that the vehicle's computer has detected an open circuit in the electrical wiring associated with the driver or passenger side mirror switch. This means the electrical circuit is incomplete, preventing the flow of current necessary for the mirror switch to function.

Symptoms: The primary symptom is the inability to adjust the power mirrors on either the driver or passenger side using the mirror switch. Other symptoms might include intermittent mirror operation or the inability to fold the power mirrors (if the vehicle is equipped with that feature). Sometimes, seemingly unrelated electrical issues might occur, although further diagnosis is needed to confirm a direct link.

Common Causes:

• Faulty Mirror Switch: The mirror switch itself can fail internally due to worn contacts or physical damage. Repeated use and age can degrade the switch's internal components, leading to an open circuit.

• Damaged Wiring Harness: The wiring harness connecting the mirror switch to the BCM is susceptible to damage, especially in the door jamb area where the harness flexes with door movement. Wires can become cut, chafed, or broken, creating an open circuit. Rodent damage is also a potential cause.

• Corroded Connectors: Moisture and environmental exposure can cause corrosion in the connectors at the mirror switch, BCM, or along the wiring harness. Corrosion creates resistance, hindering electrical flow and potentially leading to an open circuit.

• Blown Fuse: A short circuit within the mirror system can cause the fuse protecting the circuit to blow. Replacing the fuse without addressing the underlying short circuit will only result in the fuse blowing again.

• Faulty Body Control Module (BCM): While less common, the BCM itself can fail, specifically affecting the mirror control circuit. This is usually considered a last resort diagnosis after ruling out other possibilities.

Diagnostic Steps:

• Visual Inspection of Wiring: Carefully inspect the wiring harness for any signs of damage, such as cuts, chafing, or breaks. Pay particular attention to the area where the harness passes through the door jamb, as this is a common point of failure.

• Connector Inspection: Examine the connectors at the mirror switch and BCM for any signs of corrosion, loose pins, or damage. Clean any corroded connectors with electrical contact cleaner. Ensure the connectors are securely attached.

• Fuse Check: Locate the fuse that protects the power mirror system (refer to the vehicle's owner's manual or a wiring diagram). Use a multimeter or test light to check the fuse's continuity. If the fuse is blown, replace it with a fuse of the correct amperage rating.

• Mirror Switch Testing: Use a multimeter to test the continuity and resistance of the mirror switch in different positions. Refer to the vehicle's wiring diagram for the correct pinout and expected readings. A switch that shows no continuity in any position likely needs to be replaced.

• Wiring Harness Testing: Use a multimeter to test the continuity of the wiring harness between the mirror switch and the BCM. Check for shorts to ground or voltage. This involves identifying the correct wires at both ends of the circuit using a wiring diagram.

• BCM Testing: Testing the BCM typically requires specialized equipment and knowledge and is best left to a qualified technician. This usually involves using a scan tool to monitor the BCM's inputs and outputs related to the mirror control circuit.

Tools Required:

• Multimeter: An essential tool for testing voltage, continuity, and resistance in electrical circuits.

• Wiring Diagram: Crucial for identifying the correct wires and pinouts for testing and repair. These can often be found online or in vehicle repair manuals.

• Electrical Contact Cleaner: Used to clean corroded connectors and improve electrical contact.

• Wire Strippers/Crimpers: Necessary for repairing or replacing damaged wires.

• Test Light: An alternative to a multimeter for checking voltage, although it provides less detailed information.

Severity: The B1684 code indicates a moderate severity issue, as it directly impacts driving safety due to reduced visibility. Functional mirrors are essential for safe lane changes, merging, and parking.

Related Codes: Other DTCs related to the mirror system, such as B1680-B1689, may be present. These codes could indicate issues with mirror adjustment, folding, or heating functionalities.

Affected Systems: The power mirror system, specifically the driver and passenger side mirror adjustment, is directly affected by the B1684 code. The power folding function may also be impacted if equipped.

Frequently Asked Questions:

• What does the B1684 code mean? The B1684 code signifies an open circuit in the wiring of the driver or passenger side mirror switch, preventing proper mirror adjustment.

• Can I fix this problem myself? Yes, with proper tools and knowledge of automotive electrical systems, you can diagnose and potentially fix the issue. However, if you're uncomfortable working with electrical systems, it's best to consult a qualified technician.

• How do I test the mirror switch? Use a multimeter to check the continuity and resistance of the switch in various positions, referencing a wiring diagram for the correct pinout and expected values.

• Could a blown fuse cause this code? Yes, a blown fuse can definitely cause an open circuit. Check the power mirror fuse and replace it if necessary, but investigate the underlying cause of the blown fuse.

• Is the BCM always the problem? No, the BCM is rarely the cause. It's best to check all wiring, connectors, and the mirror switch before suspecting the BCM.

Conclusion:

The B1684 code indicates a problem with the electrical circuit of the power mirror switch. By systematically inspecting the wiring, connectors, fuse, and switch, you can often identify and resolve the issue. Addressing this promptly is important for maintaining safe driving conditions.