The B1708 diagnostic trouble code (DTC) signals a problem within the vehicle's power mirror system, specifically indicating that the signal from the mirror switch related to the "Right Mirror Up" function is persistently high, meaning the control module believes the button is always being pressed, even when it isn't. This can prevent proper mirror adjustment and potentially lead to other electrical issues. Understanding the causes, symptoms, and diagnostic procedures for this code is crucial for accurate troubleshooting and repair.
This article provides a comprehensive guide to the B1708 DTC, covering its meaning, potential causes, diagnostic steps, and frequently asked questions. It aims to equip technicians and vehicle owners with the knowledge needed to effectively address this issue and restore proper functionality to the power mirror system.
| Topic | Description | Relevant Information |
|---|---|---|
| Definition of B1708 | Mirror Switch R Up Input Stuck High: The control module detects a constant high voltage signal on the circuit responsible for the "Right Mirror Up" command. | Indicates an electrical fault preventing the module from correctly interpreting switch input. This often implies a short to voltage within the circuit. |
| Symptoms | Observable problems resulting from the B1708 code. | Right mirror may not move up, right mirror may move up continuously, other mirror functions may be erratic or non-functional, DTC may be accompanied by other mirror-related codes, battery drain (in severe cases). |
| Possible Causes | Potential reasons why the B1708 code is triggered. | Faulty mirror switch, short to voltage in the "Right Mirror Up" signal wire, damaged wiring harness, corroded connectors, faulty body control module (BCM) or door control module (DCM). |
| Diagnostic Tools Required | Tools necessary for diagnosing the B1708 code. | Diagnostic scan tool (capable of reading DTCs and live data), digital multimeter (DMM), wiring diagram for the vehicle's power mirror system, circuit tester, connector cleaning tools. |
| Diagnostic Steps | Step-by-step process for identifying the root cause of the B1708 code. | Verify the DTC, inspect wiring and connectors, test the mirror switch, check for shorts to voltage, test the continuity of the signal wire, check the BCM/DCM. |
| Common Mistakes | Errors frequently made during the diagnosis and repair of the B1708 code. | Replacing the mirror switch without proper diagnosis, overlooking wiring harness damage, failing to check for corrosion, neglecting to consult a wiring diagram, assuming the BCM/DCM is faulty without thorough testing. |
| Related DTCs | Other diagnostic trouble codes that may appear alongside B1708. | B1704 (Mirror Switch L Up Input Stuck High), B1705 (Mirror Switch L Down Input Stuck High), B1706 (Mirror Switch R Down Input Stuck High), B1709 (Mirror Switch L Left Input Stuck High), B1710 (Mirror Switch L Right Input Stuck High). |
| Repair Solutions | Potential fixes for resolving the B1708 code. | Replacing the faulty mirror switch, repairing or replacing damaged wiring, cleaning corroded connectors, replacing the BCM/DCM (as a last resort). |
| Importance of Wiring Diagrams | Why wiring diagrams are crucial for diagnosing electrical issues. | Provides a visual representation of the circuit, helps identify wire colors and pin locations, essential for performing accurate voltage and continuity tests, aids in tracing the signal path. |
| Safety Precautions | Safety measures to take when working on electrical systems. | Disconnect the negative battery cable before working on electrical components, use proper tools and equipment, avoid working in wet conditions, be aware of potential short circuits. |
| Testing Methodology | Methods for testing components in the power mirror circuit | Voltage Drop Testing, Continuity Testing, Resistance Measurement, Signal Verification |
Detailed Explanations
Definition of B1708: The B1708 code, "Mirror Switch R Up Input Stuck High," signifies that the vehicle's control module (often the Body Control Module or Door Control Module) is receiving a constant, unexpected high voltage signal from the mirror switch on the circuit responsible for moving the right-side mirror upwards. This means the module believes the "Up" button for the right mirror is always being pressed, even when it isn't. This constant high signal disrupts the normal operation of the power mirror system.
Symptoms: When the B1708 code is present, several symptoms may manifest. The most obvious is that the right-side mirror may not move upwards when the switch is activated. In some cases, the mirror might move upwards continuously without any input from the switch. Other mirror functions, such as left/right or down movement, might also be erratic or completely non-functional. Furthermore, other mirror-related DTCs might be present alongside B1708. In severe cases, a battery drain could occur if the circuit is constantly energized.
Possible Causes: Several factors can trigger the B1708 code. A faulty mirror switch itself is a common culprit. The switch might be internally shorted, causing the high voltage signal. A short to voltage in the "Right Mirror Up" signal wire is another likely cause. This occurs when the wire rubs against a grounded metal surface, causing the signal wire to receive voltage. A damaged wiring harness can also lead to shorts or open circuits. Corroded connectors can impede the flow of electricity and cause erratic signals. Finally, although less common, a faulty Body Control Module (BCM) or Door Control Module (DCM) can misinterpret signals or fail to control the mirror functions correctly.
Diagnostic Tools Required: To properly diagnose the B1708 code, several tools are essential. A diagnostic scan tool is needed to read the DTCs and access live data from the vehicle's computer. A digital multimeter (DMM) is crucial for measuring voltage, resistance, and continuity in the electrical circuits. A wiring diagram for the vehicle's power mirror system is indispensable for understanding the circuit layout and identifying the correct wires. A circuit tester can be used to quickly check for power and ground in the circuit. Finally, connector cleaning tools are helpful for removing corrosion from electrical connectors.
Diagnostic Steps: A systematic approach is crucial for diagnosing the B1708 code.
- Verify the DTC: Confirm that the B1708 code is present and not a historical code. Clear the code and see if it returns.
- Inspect Wiring and Connectors: Thoroughly inspect the wiring harness and connectors associated with the mirror switch and the right-side mirror motor. Look for signs of damage, such as frayed wires, broken insulation, or corroded terminals.
- Test the Mirror Switch: Use a DMM to test the mirror switch for proper operation. Refer to the wiring diagram to identify the "Right Mirror Up" signal wire. Check for continuity when the switch is pressed and released.
- Check for Shorts to Voltage: With the mirror switch disconnected, use a DMM to check for voltage on the "Right Mirror Up" signal wire. If voltage is present when it shouldn't be, there is a short to voltage in the wiring.
- Test the Continuity of the Signal Wire: Use a DMM to test the continuity of the "Right Mirror Up" signal wire between the mirror switch and the BCM/DCM. A break in the wire will result in an open circuit.
- Check the BCM/DCM: As a last resort, suspect the BCM/DCM. However, ensure all other possible causes have been ruled out before replacing these expensive components. Check for proper power and ground at the module. Consult the vehicle's service manual for specific testing procedures.
Common Mistakes: Several mistakes are commonly made during the diagnosis and repair of the B1708 code. Replacing the mirror switch without proper diagnosis is a frequent error. It's crucial to test the switch before replacing it. Overlooking wiring harness damage is another common mistake. Thoroughly inspect the wiring for any signs of damage. Failing to check for corrosion can also lead to misdiagnosis. Clean all electrical connectors to ensure good contact. Neglecting to consult a wiring diagram can make it difficult to identify the correct wires. Assuming the BCM/DCM is faulty without thorough testing is a costly mistake. Always rule out other possible causes before replacing these modules.
Related DTCs: The B1708 code may be accompanied by other mirror-related DTCs, providing additional clues about the problem. These include:
- B1704 (Mirror Switch L Up Input Stuck High)
- B1705 (Mirror Switch L Down Input Stuck High)
- B1706 (Mirror Switch R Down Input Stuck High)
- B1709 (Mirror Switch L Left Input Stuck High)
- B1710 (Mirror Switch L Right Input Stuck High)
These codes suggest issues with other mirror control circuits. Analyzing all related codes can help pinpoint the root cause of the problem.
Repair Solutions: The appropriate repair solution depends on the root cause of the B1708 code. Replacing the faulty mirror switch is often the solution if the switch is determined to be defective. Repairing or replacing damaged wiring is necessary if there is a short or open circuit in the wiring harness. Cleaning corroded connectors can restore proper electrical contact. Replacing the BCM/DCM should only be considered as a last resort after all other possible causes have been ruled out.
Importance of Wiring Diagrams: Wiring diagrams are essential for diagnosing electrical issues like the B1708 code. They provide a visual representation of the circuit, showing the location of components, the wiring connections, and the wire colors. This information is crucial for identifying the correct wires and pin locations for testing. Wiring diagrams are also essential for performing accurate voltage and continuity tests and for tracing the signal path to identify the source of the problem. Without a wiring diagram, diagnosing electrical issues can be extremely difficult and time-consuming.
Safety Precautions: When working on electrical systems, it's essential to take certain safety precautions. Disconnect the negative battery cable before working on electrical components to prevent short circuits. Use proper tools and equipment, such as insulated pliers and screwdrivers. Avoid working in wet conditions, as water can conduct electricity. Be aware of potential short circuits and take steps to prevent them.
Testing Methodology: Several testing methodologies can be employed to test the components in the power mirror circuit.
- Voltage Drop Testing: Measures the voltage drop across a wire or connection to identify areas of high resistance.
- Continuity Testing: Verifies the integrity of a wire or connection by checking for a complete circuit.
- Resistance Measurement: Measures the resistance of a component to determine if it is within the specified range.
- Signal Verification: Uses a scan tool to monitor the signal from the mirror switch to the BCM/DCM to ensure it is changing as expected.
Frequently Asked Questions
What does the B1708 code mean? It means the vehicle's computer detects a constant high voltage signal on the "Right Mirror Up" circuit, indicating a potential short or faulty switch.
Can I fix the B1708 code myself? Depending on your mechanical skills, you might be able to diagnose and repair the issue, but a wiring diagram and multimeter are essential.
What is the most common cause of B1708? A faulty mirror switch or a short to voltage in the wiring are the most common causes.
Will the B1708 code cause other problems? Besides the mirror malfunction, a constant short could drain the battery over time.
How do I clear the B1708 code? Use a diagnostic scan tool to clear the code after addressing the underlying problem.
Conclusion
The B1708 DTC, "Mirror Switch R Up Input Stuck High," indicates a specific fault within the vehicle's power mirror system. By understanding the possible causes, symptoms, and diagnostic steps outlined in this article, technicians and vehicle owners can effectively troubleshoot and repair this issue, restoring proper functionality to the power mirrors. Always prioritize safety and use appropriate tools and resources when working on electrical systems.