Introduction
The B1758 diagnostic trouble code (DTC) indicates an issue within the driver's seat rear down circuit. This circuit is responsible for controlling the downward movement of the rear portion of the driver's seat. An "open circuit" means the electrical path is broken, preventing the seat motor from receiving power and functioning correctly. This can result in the rear of the driver's seat being unable to move downwards, impacting driver comfort and potentially creating an unsafe driving position.
B1758 Fault Code: Comprehensive Overview
| Topic | Description | Possible Causes |
|---|---|---|
| Definition | B1758 is a diagnostic trouble code (DTC) indicating an open circuit within the driver's seat rear down control circuit. This means the electrical pathway that allows the seat motor to lower the rear of the driver's seat is incomplete, preventing power from reaching the motor. | * Open circuit in wiring: A break or disconnection in the wiring harness leading to the seat motor or within the motor itself. This could be due to damage, corrosion, or a loose connection. |
| * Faulty seat motor: The motor itself could be defective, preventing it from functioning even with a complete circuit. | ||
| * Faulty seat control switch: The switch that controls the rear down movement of the seat may be malfunctioning, not sending the signal to activate the motor. | ||
| * Faulty seat control module (SCM): Some vehicles utilize a seat control module to manage seat functions. A faulty SCM could prevent the signal from reaching the seat motor. | ||
| * Blown fuse or faulty relay: A blown fuse or a faulty relay in the seat control circuit can interrupt the power supply to the seat motor. | ||
| * Corrosion: Corrosion on connectors or terminals can create resistance and interrupt the electrical circuit. | ||
| * Wiring Harness Damage: Rodent damage, physical stress or chafing of the wiring harness can cause an open circuit. | ||
| Symptoms | * Rear portion of the driver's seat does not move downwards. | * The rear portion of the driver's seat may be stuck in a fixed position. |
| * Diagnostic trouble code (DTC) B1758 is stored in the vehicle's computer (ECU). | * Seat may still move in other directions (forward, backward, upward, etc.), indicating that the issue is specific to the rear down circuit. | |
| * The seat adjustment process might become noticeably slower or unresponsive. | * Other seat-related functions might be affected, depending on the vehicle's electrical system design. | |
| Troubleshooting & Repair | * Visual Inspection: Carefully inspect the wiring harness leading to the seat motor for any signs of damage, corrosion, or loose connections. | * Wiring Diagram Consultation: Obtain a wiring diagram specific to your vehicle model and year. This diagram will show the exact wiring layout for the seat control circuit and help you trace the circuit effectively. |
| * Fuse and Relay Check: Check the fuse and relay associated with the seat control circuit. Replace any blown fuses or faulty relays. | * Continuity Testing: Use a multimeter to perform continuity tests on the wiring harness. Disconnect the battery and the seat motor connector before testing. Check for continuity between the seat control switch and the seat motor connector. An absence of continuity indicates an open circuit. | |
| * Voltage Testing: Check for voltage at the seat motor connector when the seat control switch is activated. If there is no voltage, the problem lies upstream in the circuit (e.g., switch, wiring, fuse, relay, SCM). | * Seat Motor Testing: If voltage is present at the seat motor connector, the motor itself may be faulty. You can test the motor directly by applying power and ground to it. If the motor does not respond, it needs to be replaced. | |
| * Seat Control Switch Testing: Use a multimeter to test the seat control switch. Verify that the switch is sending the correct signal when activated. | * Seat Control Module (SCM) Testing (if applicable): If your vehicle has an SCM, it may require specialized diagnostic equipment to test its functionality. | |
| * Connector Cleaning: Clean all connectors and terminals associated with the seat control circuit using electrical contact cleaner. | * Wiring Repair: Repair any damaged wiring by splicing and soldering the wires together, ensuring a secure and insulated connection. | |
| * Component Replacement: Replace any faulty components, such as the seat motor, seat control switch, or seat control module. | * Professional Diagnosis: If you are unable to diagnose or repair the problem yourself, consult a qualified automotive technician. | |
| Related Codes | * B1756 Seat Driver Rear Up Circuit Open: Indicates an open circuit in the driver's seat rear up control circuit. | * B1759 Seat Driver Rear Down Circuit Short to Ground: Indicates a short circuit to ground in the driver's seat rear down control circuit. |
| * B1760 Seat Driver Rear Down Circuit Short to Battery: Indicates a short circuit to battery voltage in the driver's seat rear down control circuit. | * Other Seat Position Sensor Codes: Codes related to other seat position sensors may indicate a broader issue with the seat control system. | |
| Tools Required | * Multimeter | * Wiring Diagram (Specific to the vehicle) |
| * Electrical Contact Cleaner | * Wire Strippers/Crimpers | |
| * Soldering Iron and Solder | * Basic Hand Tools (Screwdrivers, Pliers, etc.) | |
| Severity | Moderate. While the vehicle is still drivable, the inability to adjust the seat can be uncomfortable and potentially unsafe, especially for drivers who require precise seat positioning for optimal visibility and control. |
Detailed Explanations
Definition: The B1758 DTC specifically refers to an open circuit in the driver's seat rear down circuit. This circuit is responsible for powering the seat motor to lower the rear portion of the seat. An open circuit means there's a break in the electrical path, preventing current flow. This is different from a short circuit, which would indicate an unintended path to ground or power.
Symptoms: The most obvious symptom is the inability to move the rear of the driver's seat downwards. The seat may be stuck in its current position. The check engine light may illuminate, and the B1758 code will be stored in the vehicle's computer. Other seat functions might be normal, depending on the vehicle's electrical system design.
Possible Causes: Several factors can lead to an open circuit. A damaged or disconnected wire in the harness running to the seat motor is a common culprit. Corrosion on connectors or terminals can also interrupt the electrical flow. A faulty seat motor itself could have an internal open circuit. A malfunctioning seat control switch or seat control module (SCM) (if equipped) could fail to send the signal to activate the motor. Finally, a blown fuse or faulty relay can cut off the power supply to the circuit.
Troubleshooting & Repair: The troubleshooting process involves a systematic approach to identify the location of the open circuit. Start with a visual inspection of the wiring harness for any obvious damage or loose connections. Consult a wiring diagram specific to your vehicle model to understand the circuit layout. Check the fuse and relay associated with the seat control circuit.
Use a multimeter to perform continuity tests on the wiring harness. This involves disconnecting the battery and the seat motor connector and then testing for continuity between the seat control switch and the seat motor connector. An absence of continuity indicates an open circuit.
Check for voltage at the seat motor connector when the seat control switch is activated. If there is no voltage, the problem lies upstream in the circuit (e.g., switch, wiring, fuse, relay, SCM).
If voltage is present at the seat motor connector, the motor itself may be faulty. You can test the motor directly by applying power and ground to it. If the motor does not respond, it needs to be replaced.
Clean all connectors and terminals associated with the seat control circuit using electrical contact cleaner. Repair any damaged wiring by splicing and soldering the wires together, ensuring a secure and insulated connection. Replace any faulty components, such as the seat motor, seat control switch, or seat control module.
Related Codes: B1756 (Seat Driver Rear Up Circuit Open) indicates a similar issue with the upward movement of the seat. B1759 (Seat Driver Rear Down Circuit Short to Ground) and B1760 (Seat Driver Rear Down Circuit Short to Battery) indicate short circuit conditions in the same circuit.
Tools Required: A multimeter is essential for electrical testing. A wiring diagram specific to your vehicle is crucial for understanding the circuit layout. Electrical contact cleaner helps to remove corrosion from connectors. Wire strippers/crimpers and a soldering iron are needed for wiring repairs. Basic hand tools (screwdrivers, pliers, etc.) are also necessary.
Severity: While the vehicle is still drivable, the inability to adjust the seat can be uncomfortable and potentially unsafe.
Frequently Asked Questions
What does the B1758 code mean? It indicates an open circuit in the driver's seat rear down control circuit, preventing the seat from lowering at the rear.
Can I fix this problem myself? Potentially, if you have basic automotive electrical knowledge and tools, otherwise seek a professional.
What are the most common causes of this code? Damaged wiring, corroded connectors, or a faulty seat motor are common culprits.
Do I need to replace the seat motor? Not necessarily. Thoroughly test the wiring and switch before replacing the motor.
Is it safe to drive with this code? The vehicle is generally safe to drive, but the inability to adjust the seat can be uncomfortable and potentially unsafe, if you can't find a safe driving position.
Conclusion
The B1758 DTC signifies an open circuit in the driver's seat rear down control circuit. A systematic troubleshooting process involving visual inspection, electrical testing, and component checks is necessary to identify and resolve the issue. If you're uncomfortable performing these tests, it's best to consult a qualified automotive technician.