Introduction
The B1985 Diagnostic Trouble Code (DTC) indicates a malfunction within the lumbar deflate circuit of the seat switch. This code signals that the vehicle's computer has detected an issue with the electrical circuit responsible for controlling the deflation of the lumbar support in the driver or passenger seat. Addressing this issue promptly is crucial for restoring seat comfort and ensuring proper functionality of the lumbar support system.
Comprehensive Information Table
| Topic | Description | Possible Causes |
|---|---|---|
| B1985 DTC Definition | Lumbar Deflate Circuit Failure. This code signifies that the vehicle's computer has detected a fault in the electrical circuit specifically responsible for deflating the lumbar support system in the seat. This circuit includes the switch, wiring, and the lumbar support motor or solenoid responsible for releasing air. | Short to ground in the deflate circuit, Open circuit in the deflate circuit, Faulty seat switch, Faulty lumbar support motor/solenoid, Damaged wiring harness, Corroded connectors, Faulty Body Control Module (BCM), Software issues within the BCM. |
| Symptoms of a B1985 Code | The most common symptom is a malfunctioning lumbar support. Specifically, the lumbar support may not deflate when the deflate button is pressed. Other symptoms may include intermittent lumbar support operation, a burning smell (in severe cases of short circuits), and potentially other electrical issues within the vehicle due to a compromised electrical system. | Lumbar support not deflating, Intermittent lumbar support operation, No lumbar support adjustment at all, Burning smell (rare), Other electrical issues. |
| Common Causes | The most frequent causes include a faulty seat switch, damaged wiring, corroded connectors, or a malfunctioning lumbar support motor/solenoid. A short to ground in the deflate circuit or an open circuit can also trigger the B1985 code. In rare cases, a faulty Body Control Module (BCM) or software issues within the BCM may be responsible. | Faulty seat switch, Damaged wiring, Corroded connectors, Malfunctioning lumbar support motor/solenoid, Short to ground, Open circuit, Faulty BCM, Software issues. |
| Diagnostic Steps | The diagnostic process involves several steps. First, the DTC should be verified using an OBD-II scanner. Next, a visual inspection of the seat switch, wiring harness, and connectors should be performed. A multimeter can be used to test the continuity and voltage of the circuit. If the switch is suspected, it should be tested for proper function. The lumbar support motor/solenoid should also be tested. | Verify DTC, Visual inspection, Circuit testing (continuity, voltage), Seat switch testing, Lumbar motor/solenoid testing, BCM testing (if necessary). |
| Tools Required for Diagnosis/Repair | An OBD-II scanner is essential for reading and clearing DTCs. A multimeter is needed for electrical testing. Wiring diagrams are helpful for tracing circuits. Basic hand tools, such as screwdrivers, pliers, and wire strippers, are also required. Depending on the repair, a soldering iron and heat shrink tubing may be necessary. | OBD-II scanner, Multimeter, Wiring diagrams, Basic hand tools, Soldering iron (optional), Heat shrink tubing (optional). |
| Potential Repairs | The repair will depend on the cause of the problem. If the seat switch is faulty, it will need to be replaced. Damaged wiring or corroded connectors should be repaired or replaced. A malfunctioning lumbar support motor/solenoid will also need to be replaced. In rare cases, the BCM may need to be reprogrammed or replaced. | Seat switch replacement, Wiring repair/replacement, Connector repair/replacement, Lumbar motor/solenoid replacement, BCM reprogramming/replacement (rare). |
| Wiring Diagram Importance | Wiring diagrams are critical for tracing the lumbar deflate circuit. They show the location of the switch, motor/solenoid, connectors, and wiring. They also provide information on the wire colors and pin assignments, which is essential for accurate testing and repair. Using the correct wiring diagram for your specific vehicle model and year is crucial. | Locating components, Identifying wire colors and pin assignments, Tracing the circuit, Verifying connections. |
| Seat Switch Functionality | The seat switch controls the inflation and deflation of the lumbar support. It typically has separate buttons or controls for each function. When the deflate button is pressed, the switch sends a signal to the lumbar support motor/solenoid, which then releases air from the lumbar support bladder. A faulty switch may not send the correct signal or may send no signal at all. | Controlling inflation/deflation, Sending signals to the motor/solenoid, Releasing air from the lumbar bladder. |
| Lumbar Support Motor/Solenoid | The lumbar support motor or solenoid is responsible for physically releasing air from the lumbar support bladder. When the deflate button is pressed, the motor/solenoid opens a valve, allowing air to escape. A malfunctioning motor/solenoid may not open the valve or may open it intermittently. | Releasing air from the lumbar bladder, Opening a valve to allow air to escape, Responding to signals from the seat switch. |
| Body Control Module (BCM) Role | In some vehicles, the BCM controls the lumbar support system. The seat switch sends a signal to the BCM, which then controls the lumbar support motor/solenoid. If the BCM is faulty or has software issues, it may not properly control the lumbar support system. This is less common than a faulty switch or wiring. | Receiving signals from the seat switch, Controlling the lumbar motor/solenoid, Managing the lumbar support system. |
| Safety Precautions | Always disconnect the negative battery terminal before working on electrical components. Use caution when working with wiring and connectors to avoid accidental short circuits. If you are not comfortable working on electrical systems, it is best to take your vehicle to a qualified technician. Wear appropriate safety glasses. | Disconnecting the battery, Avoiding short circuits, Seeking professional help if needed, Wearing safety glasses. |
| Related DTCs | Other DTCs related to the seat system may include codes for the seat position sensor, seat heater, or other seat-related functions. These codes can help narrow down the problem and identify other potential issues. Common related codes might include those related to seat position sensors or heating elements. | Seat position sensor codes, Seat heater codes, Other seat-related function codes. |
| Cost of Repair | The cost of repair can vary depending on the cause of the problem. A simple seat switch replacement may cost around $100-$300. More complex repairs, such as wiring harness repair or BCM replacement, can cost several hundred dollars or more. Diagnostic fees can also add to the overall cost. | Seat switch replacement cost, Wiring harness repair cost, BCM replacement cost, Diagnostic fees. |
| Preventative Measures | Regularly inspect the seat switch and wiring for any signs of damage. Avoid spills near the seat switch. If you notice any issues with the lumbar support, address them promptly to prevent further damage. Cleaning connectors periodically can help prevent corrosion. | Regular inspections, Avoiding spills, Promptly addressing issues, Cleaning connectors. |
Detailed Explanations
B1985 DTC Definition: The B1985 code is a specific diagnostic trouble code that indicates a failure within the lumbar deflate circuit. This circuit is responsible for controlling the release of air from the lumbar support bladder in the seat. The code is triggered when the vehicle's computer detects an electrical fault in this circuit, preventing the lumbar support from deflating properly.
Symptoms of a B1985 Code: The most noticeable symptom is the inability of the lumbar support to deflate when the deflate button is pressed. This can result in discomfort and difficulty finding a comfortable seating position. Other symptoms may include intermittent lumbar support operation, where the lumbar support works sometimes but not others, or a complete lack of lumbar support adjustment. In rare cases, a burning smell may be present due to a short circuit.
Common Causes: Several factors can contribute to a B1985 code. A faulty seat switch is a common culprit, as it may not send the correct signal to deflate the lumbar support. Damaged wiring or corroded connectors can also disrupt the electrical circuit. A malfunctioning lumbar support motor or solenoid, which is responsible for releasing air from the bladder, can also cause the code. In rare cases, a faulty BCM or software issues within the BCM may be responsible.
Diagnostic Steps: Diagnosing a B1985 code involves a systematic approach. First, the DTC should be verified using an OBD-II scanner. A visual inspection of the seat switch, wiring harness, and connectors should be performed to check for any obvious damage or corrosion. A multimeter can be used to test the continuity and voltage of the circuit to identify any open circuits or short circuits. The seat switch and lumbar support motor/solenoid should also be tested for proper function. If all other components check out, the BCM may need to be tested.
Tools Required for Diagnosis/Repair: An OBD-II scanner is essential for reading and clearing DTCs. A multimeter is needed for electrical testing, including voltage, resistance, and continuity. Wiring diagrams are helpful for tracing circuits and identifying components. Basic hand tools, such as screwdrivers, pliers, and wire strippers, are also required. Depending on the repair, a soldering iron and heat shrink tubing may be necessary for repairing wiring.
Potential Repairs: The repair will depend on the cause of the problem. If the seat switch is faulty, it will need to be replaced. Damaged wiring or corroded connectors should be repaired or replaced. A malfunctioning lumbar support motor/solenoid will also need to be replaced. In rare cases, the BCM may need to be reprogrammed or replaced. Always consult a repair manual or qualified technician for specific repair procedures.
Wiring Diagram Importance: Wiring diagrams are invaluable for diagnosing electrical problems, especially those involving complex systems like the seat lumbar support. They provide a visual representation of the circuit, showing the location of the switch, motor/solenoid, connectors, and wiring. They also provide information on the wire colors and pin assignments, which is essential for accurate testing and repair.
Seat Switch Functionality: The seat switch is the primary control for the lumbar support system. It allows the driver or passenger to adjust the level of lumbar support by inflating or deflating the air bladder. When the deflate button is pressed, the switch sends a signal to the lumbar support motor/solenoid, which then releases air from the bladder. A faulty switch may not send the correct signal, preventing the lumbar support from deflating.
Lumbar Support Motor/Solenoid: The lumbar support motor or solenoid is responsible for the mechanical action of releasing air from the lumbar support bladder. When the deflate button is pressed and the switch sends the appropriate signal, the motor/solenoid opens a valve, allowing air to escape. A malfunctioning motor/solenoid may not open the valve properly, preventing the lumbar support from deflating.
Body Control Module (BCM) Role: In some vehicles, the BCM plays a role in controlling the lumbar support system. The seat switch sends a signal to the BCM, which then controls the lumbar support motor/solenoid. If the BCM is faulty or has software issues, it may not properly control the lumbar support system. This is less common than a faulty switch or wiring but should be considered if other components are functioning correctly.
Safety Precautions: Always disconnect the negative battery terminal before working on electrical components to prevent accidental short circuits. Use caution when working with wiring and connectors to avoid damaging them. If you are not comfortable working on electrical systems, it is best to take your vehicle to a qualified technician. Wear appropriate safety glasses to protect your eyes.
Related DTCs: Other DTCs related to the seat system may provide additional clues about the problem. Codes for the seat position sensor, seat heater, or other seat-related functions can help narrow down the problem and identify other potential issues. Addressing these related codes may be necessary to fully resolve the B1985 code.
Cost of Repair: The cost of repair can vary significantly depending on the cause of the problem and the vehicle make and model. A simple seat switch replacement may cost around $100-$300. More complex repairs, such as wiring harness repair or BCM replacement, can cost several hundred dollars or more. Diagnostic fees can also add to the overall cost.
Preventative Measures: Regularly inspect the seat switch and wiring for any signs of damage. Avoid spills near the seat switch, as liquids can damage the electrical components. If you notice any issues with the lumbar support, address them promptly to prevent further damage. Cleaning connectors periodically can help prevent corrosion.
Frequently Asked Questions
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What does the B1985 code mean? The B1985 code indicates a failure in the lumbar deflate circuit of the seat, preventing the lumbar support from deflating. It means there's an electrical fault preventing the deflation function from working.
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What are the symptoms of a B1985 code? The main symptom is that the lumbar support will not deflate. Other symptoms might include intermittent function or a complete lack of lumbar adjustment.
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Can I fix the B1985 code myself? If you have experience with automotive electrical systems and access to the necessary tools, you may be able to diagnose and repair the problem. However, if you are not comfortable, it's best to seek professional help.
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What is the most common cause of the B1985 code? A faulty seat switch is a common cause, but damaged wiring or a malfunctioning lumbar motor/solenoid are also frequent culprits. The best way to determine the root cause is through careful diagnosis.
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How much will it cost to fix a B1985 code? The cost can vary depending on the cause, but expect to pay anywhere from $100 for a simple switch replacement to several hundred for more complex repairs. Diagnostic fees are also a factor to consider.
Conclusion
The B1985 DTC indicates a failure within the lumbar deflate circuit, leading to issues with seat comfort. A systematic approach to diagnosis and repair, starting with a visual inspection and electrical testing, will help identify the root cause and restore proper lumbar support functionality.