The B1639 diagnostic trouble code (DTC) indicates a malfunction in the circuit controlling the passenger side (right side in many regions) exterior mirror's functionality. This error can manifest in various ways, impacting the mirror's ability to adjust, heat (if equipped), or fold (if power-folding). Understanding the causes, symptoms, and potential solutions is crucial for diagnosing and resolving this issue, ensuring safe vehicle operation and optimal visibility.

Comprehensive Table of B1639 Information

Topic Description Possible Causes
Code Definition B1639: Mirror Passenger Left Circuit Failure (Note: "Left" can be misleading; on many vehicles, this code refers to the passenger side, which is the right side in countries with left-hand drive). Indicates an electrical fault in the circuit controlling one or more functions of the passenger side mirror. Short to ground: A wire in the mirror circuit is making unintended contact with the vehicle's chassis. Short to voltage: A wire in the mirror circuit is making unintended contact with a power source. Open circuit: A broken wire or connection in the mirror circuit. Faulty mirror motor(s): The motor(s) responsible for adjusting the mirror's position are malfunctioning. Faulty mirror switch: The switch used to control the mirror is malfunctioning. Faulty wiring harness or connectors: Damaged or corroded wiring or connectors in the mirror circuit. Faulty body control module (BCM): In rare cases, the BCM, which controls various electrical functions, may be the cause. Blown fuse: A blown fuse protecting the mirror circuit. Water intrusion: Water damage can cause corrosion and short circuits.
Affected Mirror Functions The B1639 code can affect various mirror functions, depending on the vehicle's features. These can include mirror adjustment (up/down/left/right), heating, turn signal (if integrated), and power folding. The specific function affected often helps narrow down the cause. For example, if only the heating function is affected, the issue may be isolated to the heating element or its wiring. If all functions are affected, the problem is more likely to be a main power or ground issue.
Common Symptoms Observable signs indicating a B1639 fault. These can range from a completely non-functional mirror to intermittent issues. Mirror does not adjust: The mirror cannot be moved using the interior control. Mirror heater does not work: The mirror does not defrost or demist. Turn signal does not work (if equipped): The turn signal integrated into the mirror does not illuminate. Power folding mirror does not fold/unfold: The mirror cannot be folded or unfolded using the interior control (if equipped). Check Engine Light (CEL) is illuminated: The vehicle's computer has detected the fault and activated the CEL. Intermittent mirror function: The mirror works sometimes, but not always. Other electrical problems: In rare cases, a B1639 code can be associated with other seemingly unrelated electrical issues.
Diagnostic Steps The process of identifying the root cause of the B1639 code. This involves systematic testing and inspection. Visual inspection: Check the mirror, wiring, and connectors for any obvious damage, corrosion, or loose connections. Fuse check: Verify that the fuse protecting the mirror circuit is not blown. Voltage and ground testing: Use a multimeter to check for proper voltage and ground at the mirror connector. Continuity testing: Use a multimeter to check for continuity in the wiring between the mirror switch and the mirror. Mirror switch testing: Test the mirror switch for proper operation. BCM testing: In rare cases, the BCM may need to be tested or reprogrammed. Scan tool diagnostics: Use a scan tool to retrieve the B1639 code and any other relevant codes. Wiring diagram review: Consult a wiring diagram for the vehicle to understand the mirror circuit layout.
Possible Solutions Actions taken to resolve the B1639 fault and restore the mirror's functionality. Repair or replace damaged wiring: Repair any broken or corroded wires. Clean or replace corroded connectors: Clean or replace corroded electrical connectors. Replace blown fuse: Replace the blown fuse with a new one of the correct amperage. Replace faulty mirror motor(s): Replace any malfunctioning mirror motors. Replace faulty mirror switch: Replace the faulty mirror switch. Replace the mirror assembly: If the damage is extensive, it may be necessary to replace the entire mirror assembly. BCM reprogramming or replacement: In rare cases, the BCM may need to be reprogrammed or replaced.
Tools Required Specific tools needed for diagnosing and repairing the B1639 fault. Multimeter: Used to measure voltage, resistance, and continuity. Scan tool: Used to retrieve diagnostic trouble codes. Wiring diagram: Used to understand the electrical circuit layout. Wire strippers and crimpers: Used for repairing or replacing wiring. Electrical contact cleaner: Used to clean corroded electrical connectors. Sockets and wrenches: Used to remove and install components. Test light: Used to check for power and ground.
Severity The level of urgency and potential impact of the B1639 code. Low to Moderate: While not immediately impacting vehicle operation, a malfunctioning side mirror can significantly reduce visibility and increase the risk of accidents. It is recommended to address the issue promptly.

Detailed Explanations

Code Definition: The B1639 code specifically points to an electrical issue within the circuit responsible for the passenger side mirror's functionality. It's crucial to remember that the term "left" in the code description can be misleading. In many vehicles, especially those with left-hand drive, the "passenger left" actually refers to the passenger side, which is the right side of the vehicle. This circuit controls various functions, such as mirror adjustment, heating, turn signal, and power folding, depending on the vehicle's features.

Affected Mirror Functions: The range of functions affected by the B1639 code depends entirely on the features equipped on the vehicle. A basic mirror might only have adjustment capabilities (up/down/left/right), while more advanced mirrors might include heating elements to defrost or demist the mirror surface, integrated turn signals for enhanced visibility, and power folding mechanisms for tight spaces or automatic folding when the vehicle is parked. Identifying which specific functions are malfunctioning helps narrow down the potential causes.

Common Symptoms: Recognizing the symptoms associated with the B1639 code is vital for accurate diagnosis. These symptoms can vary, from a completely unresponsive mirror to intermittent issues. A non-adjustable mirror, a non-functional heater, a failing turn signal (if integrated), or a power-folding mirror that refuses to fold or unfold are all potential indicators. The presence of a Check Engine Light (CEL) on the dashboard further confirms that the vehicle's computer has detected a fault in the mirror circuit.

Diagnostic Steps: Diagnosing the B1639 code requires a systematic approach. Begin with a thorough visual inspection of the mirror, wiring, and connectors, looking for any signs of damage, corrosion, or loose connections. Next, check the fuse protecting the mirror circuit to ensure it's not blown. Using a multimeter, test for proper voltage and ground at the mirror connector. Continuity testing can help identify breaks in the wiring between the mirror switch and the mirror. The mirror switch itself should also be tested for proper operation. In rare cases, the Body Control Module (BCM) may need to be tested or reprogrammed. A scan tool can retrieve the B1639 code and any other related codes. Finally, consulting a wiring diagram specific to the vehicle is essential to understand the mirror circuit's layout.

Possible Solutions: Resolving the B1639 code involves addressing the underlying cause of the electrical fault. This may include repairing or replacing damaged wiring, cleaning or replacing corroded connectors, replacing a blown fuse with one of the correct amperage, replacing faulty mirror motors, or replacing a malfunctioning mirror switch. In cases of extensive damage, replacing the entire mirror assembly may be necessary. In the rare event that the BCM is the culprit, it may need to be reprogrammed or replaced.

Tools Required: Diagnosing and repairing the B1639 code requires a selection of tools. A multimeter is essential for measuring voltage, resistance, and continuity. A scan tool is needed to retrieve diagnostic trouble codes. A wiring diagram specific to the vehicle is crucial for understanding the electrical circuit's layout. Wire strippers and crimpers are used for repairing or replacing wiring. Electrical contact cleaner helps clean corroded electrical connectors. Sockets and wrenches are needed to remove and install components. A test light can be used to check for power and ground.

Severity: The severity of a B1639 code is generally considered low to moderate. While it doesn't typically prevent the vehicle from being driven, a malfunctioning side mirror significantly reduces visibility, increasing the risk of accidents, especially when changing lanes or merging. Therefore, it's recommended to address the issue promptly to ensure safe vehicle operation.

Frequently Asked Questions

  • What does the B1639 code mean? The B1639 code indicates an electrical fault in the circuit controlling the passenger side mirror. It often means there's a short, open circuit, or faulty component in the mirror system.

  • Can I drive my car with a B1639 code? Yes, you can usually drive your car, but it's not recommended for extended periods. A malfunctioning side mirror compromises visibility and safety.

  • How do I fix a B1639 code? Fixing it involves diagnosing the cause (damaged wiring, faulty switch, etc.) and repairing or replacing the affected components. Professional diagnosis is often recommended.

  • Is the B1639 code serious? It's moderately serious because it affects visibility. It should be addressed promptly to ensure safe driving.

  • Could a blown fuse cause the B1639 code? Yes, a blown fuse protecting the mirror circuit can cause the B1639 code. Checking and replacing the fuse is a good first step.

Conclusion

The B1639 "Mirror Passenger Left Circuit Failure" code indicates an electrical problem in the passenger side mirror circuit, potentially affecting various mirror functions. A systematic diagnostic approach, utilizing appropriate tools and resources like wiring diagrams, is crucial for accurately identifying and resolving the underlying cause, ensuring safe vehicle operation and optimal visibility.