Introduction:
The B1738 Diagnostic Trouble Code (DTC) signifies a problem within the mirror driver circuit, specifically related to the horizontal switch. This code indicates that the vehicle's computer, often the Body Control Module (BCM), has detected an open circuit in the wiring or components responsible for controlling the horizontal movement of the side mirrors. This malfunction can prevent the driver from adjusting the mirrors horizontally, impacting visibility and driving safety.
Comprehensive Table: B1738 Mirror Driver Horizontal Switch Circuit Open
| Aspect | Description | Possible Causes |
|---|---|---|
| Definition | An open circuit exists in the horizontal switch control circuit of the mirror driver. The BCM is unable to send or receive signals to/from the mirror motor for horizontal adjustments. | Disconnected or Damaged Wiring: Broken, frayed, corroded, or shorted wires in the mirror adjustment circuit. Faulty Mirror Switch: The switch itself is malfunctioning, preventing proper signal transmission. Defective Mirror Motor: The motor responsible for horizontal movement has failed. BCM Malfunction: In rare cases, a faulty Body Control Module could be the root cause. Connector Issues: Loose, corroded, or damaged connectors within the circuit. Fuse/Relay Problems: A blown fuse or faulty relay (if applicable) in the mirror circuit. |
| Symptoms | Inability to adjust the side mirror horizontally (left/right). The mirror may be stuck in one position. Diagnostic Trouble Code (DTC) B1738 is stored in the vehicle's computer. The mirror adjustment may work intermittently or not at all. Other mirror functions (vertical adjustment, heating) may still work if they are on separate circuits. | |
| Diagnostic Steps | Visual inspection of wiring and connectors. Testing the mirror switch for continuity and proper function. Checking the mirror motor for resistance and proper operation. Using a multimeter to test for voltage and continuity in the circuit. Scanning the vehicle's computer for related DTCs. Checking fuses and relays associated with the mirror circuit. Inspecting the wiring harness for damage. Testing the BCM output signal for the mirror adjustment circuit. Consulting the vehicle's service manual for specific wiring diagrams and troubleshooting procedures. | |
| Common Components Involved | Mirror Switch, Mirror Motor (Horizontal Adjustment), Wiring Harness, Connectors, Body Control Module (BCM), Fuses, Relays (if applicable). | |
| Severity | Moderate. While not a critical safety issue like braking or steering malfunctions, the inability to adjust the mirrors horizontally can significantly impair visibility and increase the risk of accidents. | |
| Potential Solutions | Repair or replace damaged wiring. Replace the faulty mirror switch. Replace the defective mirror motor. Replace the Body Control Module (BCM) if diagnosed as faulty (requires programming). Clean or replace corroded connectors. Replace blown fuses or faulty relays. Consult a qualified mechanic for diagnosis and repair. | |
| Related DTCs | Other DTCs related to mirror control circuits, such as codes for vertical adjustment malfunctions or heating element failures. DTCs related to the Body Control Module (BCM). DTCs indicating short circuits or other electrical problems in the mirror circuit. | |
| Tools Required | Multimeter, Wiring Diagram, Socket Set, Screwdriver Set, Wire Strippers, Wire Crimpers, Test Light, Scan Tool (for reading DTCs), Connector Cleaning Tool. | |
| Estimated Repair Cost | Varies depending on the cause and the vehicle model. Simple wiring repairs may cost $50-$150. Mirror switch replacement may cost $100-$300. Mirror motor replacement may cost $200-$500. BCM replacement and programming can be significantly more expensive, potentially ranging from $500 to $1500 or more. | |
| Preventative Measures | Regularly inspect wiring and connectors for damage or corrosion. Avoid excessive force when adjusting the mirrors. Protect the mirror assembly from impact. Address any intermittent mirror adjustment problems promptly. |
Detailed Explanations:
Definition: The B1738 code indicates that the vehicle's computer has detected an open circuit in the horizontal switch control circuit of the mirror driver. This means the circuit is broken, preventing the flow of electricity necessary to control the horizontal movement of the side mirror. The BCM, which manages various electronic functions, is unable to communicate with the mirror motor for left and right adjustments.
Symptoms: The most obvious symptom is the inability to adjust the side mirror horizontally. The mirror may be stuck in a fixed position. The B1738 DTC will be stored in the vehicle's computer and can be retrieved using a scan tool. Other mirror functions, such as vertical adjustment or heating, might still work if they operate on separate circuits. Intermittent functionality can also be a symptom, where the mirror works sometimes but not others.
Diagnostic Steps: A systematic approach is crucial for diagnosing the B1738 code. Start with a visual inspection of the wiring and connectors related to the mirror. Check for any signs of damage, corrosion, or loose connections. Test the mirror switch for continuity and proper function using a multimeter. Next, check the mirror motor for resistance and proper operation. Use a multimeter to test for voltage and continuity in the circuit. A scan tool can be used to scan the vehicle's computer for related DTCs. Check fuses and relays associated with the mirror circuit. Inspect the wiring harness for any signs of damage. If necessary, test the BCM output signal for the mirror adjustment circuit. Always consult the vehicle's service manual for specific wiring diagrams and troubleshooting procedures.
Common Components Involved: Several components can contribute to the B1738 code. The mirror switch is responsible for sending the adjustment signals. The mirror motor (horizontal adjustment) physically moves the mirror. The wiring harness and connectors provide the electrical pathways. The Body Control Module (BCM) controls various vehicle functions, including mirror adjustment. Fuses and relays (if applicable) protect and control the circuit.
Severity: The severity of the B1738 code is considered moderate. While not as critical as brake or steering malfunctions, the inability to adjust the side mirrors horizontally can significantly impair visibility and increase the risk of accidents. Proper mirror adjustment is essential for safe driving, especially when changing lanes or merging.
Potential Solutions: The solution depends on the root cause of the problem. Repairing or replacing damaged wiring is a common fix. If the mirror switch is faulty, replacing the switch is necessary. A defective mirror motor requires replacement of the motor. In rare cases, a faulty Body Control Module (BCM) may need to be replaced and programmed. Corroded connectors should be cleaned or replaced. Blown fuses or faulty relays should be replaced. Consulting a qualified mechanic for diagnosis and repair is recommended.
Related DTCs: Other DTCs related to the mirror control circuits, such as codes for vertical adjustment malfunctions or heating element failures, may be present. DTCs related to the Body Control Module (BCM) could also be present. DTCs indicating short circuits or other electrical problems in the mirror circuit can also be related and helpful in narrowing down the problem.
Tools Required: Diagnosing and repairing the B1738 code requires several tools. A multimeter is essential for testing voltage, continuity, and resistance. A wiring diagram is crucial for understanding the circuit layout. A socket set and screwdriver set are needed for removing and installing components. Wire strippers and wire crimpers are used for repairing wiring. A test light can be used to check for power and ground. A scan tool is necessary for reading DTCs. A connector cleaning tool can help remove corrosion from connectors.
Estimated Repair Cost: The cost of repair varies depending on the cause and the vehicle model. Simple wiring repairs may cost $50-$150. Mirror switch replacement may cost $100-$300. Mirror motor replacement may cost $200-$500. BCM replacement and programming can be significantly more expensive, potentially ranging from $500 to $1500 or more. These are just estimates, and the actual cost may vary depending on the labor rates and parts prices in your area.
Preventative Measures: Regularly inspecting wiring and connectors for damage or corrosion can help prevent the B1738 code. Avoid using excessive force when adjusting the mirrors. Protect the mirror assembly from impact. Addressing any intermittent mirror adjustment problems promptly can prevent them from escalating into more serious issues.
Frequently Asked Questions:
Question: What does the B1738 code mean? Answer: It means there's an open circuit in the horizontal mirror adjustment circuit, preventing the mirror from moving left or right.
Question: Can I fix the B1738 code myself? Answer: If you have experience with automotive electrical systems and the necessary tools, you might be able to diagnose and repair the issue, but professional help is recommended if you're not comfortable.
Question: How important is it to fix the B1738 code? Answer: While not immediately critical, it impacts visibility and safety, so it's best to address it promptly.
Question: Will the B1738 code affect other functions of my car? Answer: Generally, no, but it could indicate a broader electrical problem if other related codes are present.
Question: Can a bad fuse cause the B1738 code? Answer: Yes, a blown fuse in the mirror circuit could cause an open circuit and trigger the B1738 code.
Conclusion:
The B1738 code indicates a problem with the horizontal mirror adjustment circuit, leading to impaired visibility. A systematic diagnostic approach, starting with visual inspection and electrical testing, is crucial for identifying the root cause and implementing the appropriate repair. It's advisable to consult a qualified mechanic for diagnosis and repair to ensure proper functionality and safety.