The B1640 diagnostic trouble code (DTC) indicates an issue with the passenger side (left in some vehicle configurations) mirror circuit. This code specifically points to an open circuit, meaning the electrical pathway for the mirror's functions (adjustment, heating, signals, etc.) is incomplete. Troubleshooting this code requires careful examination of the wiring, connectors, and the mirror assembly itself.
This issue can affect the functionality of the passenger side mirror, impacting visibility and safety. Addressing the B1640 code promptly is essential for restoring full mirror functionality and ensuring safe driving conditions.
| Topic | Description | Possible Causes |
|---|---|---|
| Definition | B1640 indicates an open circuit in the passenger side mirror control circuit. | Broken wire, loose connection, faulty mirror motor, damaged mirror switch, or a problem with the vehicle's body control module (BCM). |
| Affected Functions | Mirror adjustment (up/down, left/right), heated mirror (if equipped), turn signal (if equipped). | Loss of mirror adjustment control, inoperative heated mirror, or non-functional turn signal in the mirror. |
| Common Symptoms | Passenger side mirror not working, DTC B1640 stored in the vehicle's computer. | Mirror does not move when attempting to adjust, heated mirror does not defrost, turn signal in the mirror does not illuminate. |
| Diagnostic Tools | Multimeter, wiring diagram, scan tool (OBD-II scanner). | Multimeter to test for voltage and continuity, wiring diagram to trace the circuit, scan tool to read and clear DTCs. |
| Wiring Diagram Importance | Essential for tracing the circuit and identifying potential breaks or shorts. | Helps to pinpoint the specific wires and connectors involved in the mirror circuit. |
| Connector Inspection | Check for corrosion, loose pins, or damage. | Corrosion can increase resistance, loose pins can cause intermittent connection, and damage can break the circuit. |
| Mirror Motor Testing | Test the mirror motor for proper operation using a multimeter and applying power directly. | A faulty motor will not respond to direct power, indicating the need for replacement. |
| Heated Mirror Element Testing | Test the heated mirror element for continuity using a multimeter. | An open circuit in the heating element indicates a fault that requires replacement of the mirror glass or the entire mirror assembly. |
| Turn Signal Testing (Mirror) | Test the turn signal element for proper function using a multimeter and applying power directly. | If the turn signal element doesn't illuminate with direct power, it requires replacement. |
| Mirror Switch Testing | Test the mirror switch for continuity and proper operation. | A faulty switch can prevent power from reaching the mirror motor or other components. |
| Body Control Module (BCM) | The BCM controls various vehicle functions, including the power mirrors. A faulty BCM can cause B1640. | If all other components test good, a faulty BCM may be the cause. Requires professional diagnosis and possibly reprogramming. |
| Open Circuit Troubleshooting | Identify the location of the break in the circuit using a multimeter and wiring diagram. | Look for damaged wires, corroded connectors, or broken solder joints. |
| Short Circuit Troubleshooting | While B1640 indicates an open circuit, shorts can also cause related issues. Identify shorts to ground. | Look for wires rubbing against metal surfaces or damaged insulation. |
| Repair Procedures | Repair or replace damaged wires, connectors, or components. | Splicing wires, replacing connectors, replacing the mirror motor, replacing the mirror assembly, or replacing the BCM. |
| Component Replacement | Ensure the replacement component is compatible with the vehicle. | Use the correct part number or a suitable replacement from a reputable supplier. |
| Post-Repair Verification | Clear the DTC and verify that the mirror functions correctly. | Use a scan tool to clear the DTC. Test all mirror functions (adjustment, heating, turn signal) to ensure they are working properly. |
| Related DTCs | Other DTCs related to the mirror circuit or BCM. | B1635-B1639 (other mirror circuit issues), U-codes (communication errors with the BCM). |
| Safety Precautions | Disconnect the battery before working on the electrical system. | Prevents electrical shock and damage to the vehicle's electrical components. |
| Technical Service Bulletins (TSBs) | Check for TSBs related to the B1640 code on the specific vehicle model. | TSBs may provide specific diagnostic and repair procedures for known issues. |
| Vehicle Specific Information | Wiring diagrams and component locations vary depending on the vehicle make, model, and year. | Consult the vehicle's service manual or a reputable online database for accurate information. |
| Cost Considerations | Repair costs vary depending on the cause of the problem and the parts required. | Simple wire repairs are relatively inexpensive. Component replacement (mirror motor, mirror assembly, BCM) can be more costly. |
| DIY vs. Professional Repair | Simple repairs (wire splicing, connector replacement) can be done DIY. Complex repairs require a professional. | If you are not comfortable working with electrical systems, it is best to seek professional help. |
Detailed Explanations
Definition: The B1640 code signifies that the vehicle's computer has detected an open circuit within the electrical system controlling the passenger side mirror. An open circuit means there's a break in the electrical pathway, preventing current flow and disabling the mirror's functions.
Affected Functions: This open circuit directly impacts the functionality of the passenger side mirror. This can include the inability to adjust the mirror's position (up/down, left/right), the failure of the heated mirror element to defrost the glass in cold weather (if equipped), and the deactivation of the turn signal integrated into the mirror (if equipped).
Common Symptoms: The most obvious symptom is the passenger side mirror not working at all. You may also see the B1640 code displayed by a scan tool connected to the vehicle's OBD-II port. This can manifest as the mirror refusing to move during adjustment attempts, the heated mirror failing to defrost, or the turn signal in the mirror failing to illuminate.
Diagnostic Tools: The primary tools for diagnosing B1640 include a multimeter for testing voltage and continuity, a wiring diagram specific to the vehicle to trace the circuit, and a scan tool to read and clear DTCs. These tools allow you to systematically check the electrical components and wiring involved in the mirror circuit.
Wiring Diagram Importance: A wiring diagram is crucial for understanding the specific layout of the mirror circuit in your vehicle. It shows the location of wires, connectors, and components, allowing you to trace the circuit and pinpoint potential breaks or shorts accurately. Without a wiring diagram, troubleshooting becomes significantly more difficult and time-consuming.
Connector Inspection: Thoroughly inspect all connectors in the mirror circuit for signs of corrosion, loose pins, or physical damage. Corrosion can increase resistance and impede current flow, loose pins can cause intermittent connections, and physical damage can break the circuit entirely. Clean corroded connectors and ensure pins are securely seated.
Mirror Motor Testing: To test the mirror motor, disconnect it from the vehicle's wiring harness and apply power directly from a 12V source. If the motor does not respond, it's likely faulty and needs to be replaced. This test isolates the motor and eliminates other potential causes of the open circuit.
Heated Mirror Element Testing: The heated mirror element can be tested for continuity using a multimeter. Disconnect the element and measure the resistance across its terminals. An open circuit (infinite resistance) indicates a faulty heating element that requires replacement.
Turn Signal Testing (Mirror): Similar to the mirror motor, the turn signal element can be tested by disconnecting it and applying direct power. If the element does not illuminate, it's faulty and needs to be replaced.
Mirror Switch Testing: The mirror switch controls power to the mirror motor and other functions. Use a multimeter to test the switch for continuity in each position. A faulty switch can prevent power from reaching the mirror, even if the wiring and motor are good.
Body Control Module (BCM): The BCM is a central computer that controls various vehicle functions, including the power mirrors. If all other components test good, a faulty BCM could be the cause of the B1640 code. Diagnosing a BCM issue typically requires specialized tools and expertise.
Open Circuit Troubleshooting: Identifying the location of the open circuit requires careful tracing of the wiring using a multimeter and the wiring diagram. Look for damaged wires, corroded connectors, or broken solder joints. Test for continuity between different points in the circuit to isolate the break.
Short Circuit Troubleshooting: While B1640 specifically indicates an open circuit, related issues can be caused by shorts to ground. Inspect the wiring for damage, such as wires rubbing against metal surfaces or compromised insulation. A short circuit can drain power and potentially damage other components.
Repair Procedures: Repairing the B1640 code may involve splicing damaged wires, replacing corroded connectors, replacing the mirror motor, replacing the entire mirror assembly, or, in rare cases, replacing the BCM. The specific repair will depend on the cause of the open circuit.
Component Replacement: When replacing components, ensure the replacement part is compatible with the vehicle's make, model, and year. Using the wrong part can lead to further problems and may not resolve the B1640 code.
Post-Repair Verification: After completing the repair, clear the B1640 code using a scan tool and verify that the mirror functions correctly. Test all mirror functions (adjustment, heating, turn signal) to ensure they are working properly.
Related DTCs: Other DTCs related to the mirror circuit or the BCM can provide additional clues about the problem. These may include codes for other mirror circuit issues (B1635-B1639) or communication errors with the BCM (U-codes).
Safety Precautions: Always disconnect the battery before working on the electrical system to prevent electrical shock and damage to the vehicle's electrical components. This is a crucial safety precaution.
Technical Service Bulletins (TSBs): Check for TSBs related to the B1640 code for the specific vehicle model. TSBs may provide specific diagnostic and repair procedures for known issues.
Vehicle Specific Information: Wiring diagrams and component locations vary depending on the vehicle's make, model, and year. Consult the vehicle's service manual or a reputable online database for accurate information.
Cost Considerations: Repair costs vary depending on the cause of the problem and the parts required. Simple wire repairs are relatively inexpensive. Component replacement (mirror motor, mirror assembly, BCM) can be more costly.
DIY vs. Professional Repair: Simple repairs (wire splicing, connector replacement) can be done DIY. Complex repairs involving the BCM or extensive wiring issues require a professional. If you are not comfortable working with electrical systems, it is best to seek professional help.
Frequently Asked Questions
What does the B1640 code mean? It indicates an open circuit in the passenger side mirror control circuit, preventing the mirror from functioning properly.
What are the symptoms of a B1640 code? The passenger side mirror may not adjust, the heated mirror may not work, and the turn signal in the mirror may be inoperative.
Can I fix the B1640 code myself? Simple repairs like wire splicing or connector replacement can be DIY, but complex repairs may require a professional.
What tools do I need to diagnose a B1640 code? You'll need a multimeter, a wiring diagram for your vehicle, and a scan tool to read and clear DTCs.
Is a faulty BCM the only cause of B1640? No, other causes include broken wires, loose connections, and a faulty mirror motor. The BCM is usually the last to be checked.
Conclusion
The B1640 DTC signals a break in the electrical circuit controlling the passenger side mirror, leading to functional impairments. Thorough diagnosis using a multimeter, wiring diagram, and scan tool is crucial for pinpointing the source of the open circuit and implementing the appropriate repair, be it a simple wire fix or component replacement.