The B1845 diagnostic trouble code (DTC) indicates a malfunction within the driver's seat lumbar support system, specifically concerning the "down" switch circuit. This code signals that the vehicle's computer has detected an issue with the electrical circuit responsible for activating the downward movement of the lumbar support. Addressing this issue promptly is crucial to ensure proper functionality of the lumbar support system, which is essential for driver comfort and preventing back pain during long drives.
Comprehensive Information on B1845
| Topic | Description | Possible Causes |
|---|---|---|
| Code Definition | Driver Lumbar Down Switch Circuit Malfunction | Shorted or open circuit in the down switch wiring, faulty down switch, failed lumbar motor, wiring harness damage, loose connections, corroded terminals, faulty seat control module (SCM), low voltage, PCM malfunction (rare). |
| Affected System | Driver's Seat Lumbar Support | Reduced lumbar support, inability to adjust lumbar support downwards, intermittent lumbar support function, complete loss of lumbar support function. |
| Symptoms | Lumbar support will not move downwards, lumbar support may be stuck in the "up" position, no response from the lumbar down switch, intermittent operation. | Check engine light (CEL) illumination, stored DTC B1845 in vehicle's computer, possible other seat-related DTCs. |
| Diagnostic Steps | Visual inspection of wiring and connectors, testing the lumbar down switch, checking voltage at the switch and motor, testing the lumbar motor, module testing. | Multimeter, test light, wiring diagram, scan tool (for reading and clearing codes, module activation). |
| Common Causes | Faulty lumbar down switch, broken or damaged wiring, corroded connectors. | Replacing the lumbar down switch, repairing or replacing damaged wiring, cleaning or replacing corroded connectors. |
| Severity | Low to Moderate | Driver discomfort, potential back pain, reduced resale value. |
| Related Codes | B1843 (Driver Lumbar Up Switch Circuit Malfunction), B1847 (Driver Lumbar Forward Switch Circuit Malfunction), B1849 (Driver Lumbar Rearward Switch Circuit Malfunction). | Could point towards a wider problem in the seat control system. |
| Component Locations | Lumbar down switch (typically located on the side of the driver's seat), lumbar motor (inside the seat back), seat control module (usually under the seat). | Locate these components by consulting your vehicle's repair manual. |
| Wiring Diagram Importance | Essential for tracing the circuit and identifying potential breaks or shorts. | Obtain a wiring diagram specific to your vehicle's make, model, and year. |
| Tools Required | Multimeter, test light, wire stripper/crimper, connector cleaner, socket set, wrench set. | Ensure you have the correct tools before starting any diagnostic or repair work. |
| Potential Impact on Other Systems | None typically, unless the short circuit is severe and affects other circuits. | Check for any other unusual electrical behavior in the vehicle. |
| Testing the Lumbar Motor | Apply direct voltage to the motor to check for functionality. | Consult your vehicle's repair manual for the correct voltage and polarity. |
| Testing the Switch | Use a multimeter to check for continuity when the switch is pressed. | The switch should show continuity when pressed and no continuity when released. |
| Checking for Voltage Drops | Measure the voltage at various points in the circuit to identify areas of excessive voltage drop, indicating a problem with the wiring or connections. | A voltage drop of more than 0.5 volts can indicate a problem. |
| Seat Control Module (SCM) Testing | Requires a scan tool that can communicate with the SCM. | This test can help determine if the SCM is functioning correctly and sending the proper signals to the lumbar motor. |
| Connector Inspection | Look for corrosion, loose connections, and damaged wires. | Clean any corrosion with a connector cleaner and repair any damaged wires. |
| Safety Precautions | Disconnect the battery before working on the electrical system. | This will prevent accidental shocks or damage to the electrical system. |
| Repair vs. Replacement | Repair damaged wiring or connectors whenever possible. Replace faulty components, such as the switch or motor. | Consider the cost and availability of parts when deciding whether to repair or replace a component. |
| After Repair Verification | Clear the DTC and retest the system to ensure the problem is resolved. | If the DTC returns, further diagnosis may be necessary. |
| Professional Assistance | If you are not comfortable working on the electrical system, seek professional assistance from a qualified mechanic. | A mechanic will have the necessary tools and expertise to diagnose and repair the problem correctly. |
| Impact on Vehicle Safety | Minimal direct impact on vehicle safety, but driver fatigue and discomfort due to lack of proper lumbar support can indirectly affect driving performance. | Ensure the lumbar support system is functioning correctly for optimal driver comfort and safety. |
| Data Logging | Use a scan tool to log data from the seat control module while operating the lumbar switch. | This can help identify intermittent problems or unusual behavior in the system. |
| Power and Ground Circuits | Verify that the power and ground circuits to the lumbar motor and switch are functioning correctly. | A poor ground can cause intermittent problems or a complete failure of the system. |
| Checking for Open Circuits | Use a multimeter to check for continuity in the wiring between the switch and the lumbar motor. | An open circuit indicates a break in the wiring. |
| Checking for Short Circuits | Use a multimeter to check for shorts to ground in the wiring. | A short circuit can cause the lumbar motor to run continuously or blow a fuse. |
| Fuse Location and Inspection | Locate the fuse for the seat control system and inspect it for damage. | A blown fuse can indicate a short circuit or an overload in the system. |
Detailed Explanations
Code Definition: The B1845 code specifically identifies a problem within the electrical circuit controlling the downward movement of the driver's seat lumbar support. This means the vehicle's computer, often the Powertrain Control Module (PCM) or Body Control Module (BCM), has detected an abnormality in the voltage or current flow associated with that particular switch circuit.
Affected System: The affected system is solely the driver's seat lumbar support. This system is designed to provide adjustable support to the lower back, enhancing comfort and reducing fatigue, particularly during long drives. The lumbar support usually moves up, down, forward, and backward to customize the level of support.
Symptoms: The most obvious symptom is the inability to move the lumbar support downward. Other symptoms might include the lumbar support being stuck in the "up" position, a complete lack of response when the "down" switch is pressed, or intermittent operation where the lumbar support sometimes works and sometimes doesn't.
Diagnostic Steps: The diagnostic process involves a systematic approach, beginning with a visual inspection of the wiring and connectors associated with the lumbar support system. Next, the lumbar down switch should be tested for proper function, followed by checking the voltage at the switch and motor. The lumbar motor itself needs to be tested to ensure it's operating correctly. Finally, the seat control module may need to be tested using a scan tool.
Common Causes: The most frequent culprits behind the B1845 code are a faulty lumbar down switch, broken or damaged wiring in the circuit, and corroded connectors that impede electrical flow. Internal failure of the lumbar support motor is also possible, though less common.
Severity: The severity of this issue is generally considered low to moderate. While it doesn't directly impact the vehicle's safety, the lack of proper lumbar support can cause driver discomfort and potential back pain, especially on long journeys. It can also slightly reduce the resale value of the vehicle.
Related Codes: Other related codes can provide additional clues. B1843 (Driver Lumbar Up Switch Circuit Malfunction) could suggest a problem with the entire switch assembly. B1847 (Driver Lumbar Forward Switch Circuit Malfunction) and B1849 (Driver Lumbar Rearward Switch Circuit Malfunction) could indicate a more widespread issue within the seat's control system.
Component Locations: The lumbar down switch is typically located on the side of the driver's seat, easily accessible for adjustment. The lumbar motor resides inside the seat back, controlling the inflation and deflation of the lumbar support bladder. The seat control module (SCM) is often found underneath the seat. Consulting your vehicle's repair manual will provide precise locations.
Wiring Diagram Importance: A wiring diagram is indispensable for tracing the circuit and pinpointing potential breaks or shorts. It illustrates the electrical pathways, components, and connections within the lumbar support system, allowing for accurate diagnostics.
Tools Required: Essential tools include a multimeter for measuring voltage and continuity, a test light for checking for power, a wire stripper/crimper for repairing wiring, connector cleaner for removing corrosion, and a socket and wrench set for accessing components.
Potential Impact on Other Systems: In most cases, a B1845 code will not affect other vehicle systems. However, a severe short circuit could potentially impact other electrical circuits. It's always wise to check for any other unusual electrical behavior in the vehicle.
Testing the Lumbar Motor: To test the lumbar motor, you can apply direct voltage to it. Consult your vehicle's repair manual for the correct voltage and polarity. If the motor doesn't respond, it may be faulty and require replacement.
Testing the Switch: Use a multimeter to check for continuity when the lumbar down switch is pressed. The switch should show continuity when pressed and no continuity when released. If it doesn't behave as expected, the switch is likely faulty.
Checking for Voltage Drops: Measure the voltage at various points in the circuit to identify areas of excessive voltage drop. A voltage drop of more than 0.5 volts can indicate a problem with the wiring or connections, such as corrosion or a loose connection.
Seat Control Module (SCM) Testing: Testing the SCM requires a scan tool that can communicate with the module. This test can determine if the SCM is functioning correctly and sending the proper signals to the lumbar motor.
Connector Inspection: Carefully inspect all connectors associated with the lumbar support system for corrosion, loose connections, and damaged wires. Clean any corrosion with a connector cleaner and repair any damaged wires.
Safety Precautions: Always disconnect the battery before working on the electrical system to prevent accidental shocks or damage to the electrical system.
Repair vs. Replacement: Whenever possible, repair damaged wiring or connectors. Replace faulty components, such as the switch or motor. Consider the cost and availability of parts when deciding whether to repair or replace a component.
After Repair Verification: After completing any repairs, clear the DTC using a scan tool and retest the system to ensure the problem is resolved. If the DTC returns, further diagnosis may be necessary.
Professional Assistance: If you are not comfortable working on the electrical system, seek professional assistance from a qualified mechanic. A mechanic will have the necessary tools and expertise to diagnose and repair the problem correctly.
Impact on Vehicle Safety: The direct impact on vehicle safety is minimal. However, driver fatigue and discomfort due to lack of proper lumbar support can indirectly affect driving performance.
Data Logging: Use a scan tool to log data from the seat control module while operating the lumbar switch. This can help identify intermittent problems or unusual behavior in the system.
Power and Ground Circuits: Verify that the power and ground circuits to the lumbar motor and switch are functioning correctly. A poor ground can cause intermittent problems or a complete failure of the system.
Checking for Open Circuits: Use a multimeter to check for continuity in the wiring between the switch and the lumbar motor. An open circuit indicates a break in the wiring.
Checking for Short Circuits: Use a multimeter to check for shorts to ground in the wiring. A short circuit can cause the lumbar motor to run continuously or blow a fuse.
Fuse Location and Inspection: Locate the fuse for the seat control system and inspect it for damage. A blown fuse can indicate a short circuit or an overload in the system.
Frequently Asked Questions
What does the B1845 code mean? The B1845 code signifies a malfunction in the driver's seat lumbar support system, specifically the circuit controlling the downward movement. It means the vehicle's computer has detected an issue with the switch or wiring related to that function.
What are the symptoms of a B1845 code? The primary symptom is the lumbar support not moving downwards when the switch is pressed. Other symptoms may include the lumbar being stuck in the "up" position or intermittent operation.
Can I fix the B1845 code myself? Depending on your mechanical skills, you might be able to diagnose and fix the problem. Start with a visual inspection and testing the switch and wiring; otherwise, seek professional help.
Is the B1845 code a serious issue? While it doesn't directly impact vehicle safety, it can cause discomfort and potential back pain, especially on long drives, and may slightly reduce resale value.
How much does it cost to fix a B1845 code? The cost varies depending on the cause and the mechanic's labor rates. A simple switch replacement might be relatively inexpensive, while a faulty control module could be significantly more costly.
Conclusion
The B1845 code indicates a problem with the driver's seat lumbar down switch circuit, potentially caused by a faulty switch, damaged wiring, or a malfunctioning motor. Thorough diagnostics and proper repairs are essential to restore lumbar support functionality and driver comfort.