B1955 Seat Front Up/Down Potentiometer Feedback Circuit Open

Introduction:

The B1955 diagnostic trouble code (DTC) indicates an issue within the feedback circuit of the seat's front up/down potentiometer. This potentiometer is a crucial component of the power seat system, providing the seat control module with information about the seat's position. When this circuit is open, the module loses the ability to accurately determine the seat's height, potentially leading to malfunctioning seat adjustments. This article will explore the causes, symptoms, diagnosis, and repair of the B1955 code.

Topic	Description	Potential Impact
Code Definition	B1955: Seat Front Up/Down Potentiometer Feedback Circuit Open	Malfunctioning seat adjustments, inability to save seat positions (if equipped), potential passenger discomfort.
Potentiometer Function	Variable resistor that changes resistance based on seat height; sends a voltage signal to the seat control module	Inaccurate seat position data, preventing the seat control module from precisely controlling the seat motors.
Circuit Components	Potentiometer, wiring harness, connectors, seat control module	Failure in any of these components can trigger the B1955 code.
Common Causes	Open circuit in wiring, corroded connectors, faulty potentiometer, damaged seat control module.	Interrupted signal transmission, incorrect resistance readings, preventing proper seat function.
Symptoms	Seat not moving up or down, intermittent seat movement, inability to save seat positions, DTC B1955 present.	Frustration for the driver and passengers, potential safety concerns related to seat position.
Diagnostic Tools	Multimeter, scan tool, wiring diagrams	Essential for testing circuit continuity, identifying faulty components, and confirming the repair.
Diagnostic Procedure	Visual inspection, circuit testing (voltage, resistance, continuity), potentiometer testing, module testing.	Systematic approach to isolate the root cause of the problem.
Repair Procedures	Wiring repair (splicing, replacement), connector cleaning/replacement, potentiometer replacement, module replacement.	Restoring the integrity of the circuit and replacing faulty components.
Related DTCs	B1954 (Short to Ground), B1956 (Short to Voltage), other seat-related DTCs.	May indicate related issues within the seat control system.
Affected Vehicle Systems	Power seat system, body control module (BCM), seat control module.	Interconnected systems that rely on accurate seat position information.
Safety Precautions	Disconnect battery, be careful when working with electrical components, consult the vehicle's service manual.	Preventing electrical shock and damage to vehicle components.
Calibration/Programming Needs	Possible seat control module programming after replacement.	Ensuring the new module functions correctly with the vehicle's other systems.
Wiring Harness Inspection	Check for chafing, kinks, or damage to the wiring harness leading to the potentiometer.	Prevent further shorts or open circuits in the future.
Connector Corrosion	Check for corrosion at the connectors of the potentiometer and the seat control module.	Clean or replace corroded connectors to ensure proper signal transmission.
Potentiometer Resistance Range	Refer to the vehicle's service manual for the correct resistance range for the potentiometer.	Ensure the potentiometer is functioning within the specified parameters.
Ground Circuit Integrity	Verify the ground circuit for the seat control module is intact and providing a good ground connection.	A faulty ground can cause a variety of electrical problems, including the B1955 code.
Seat Motor Function	While addressing B1955, confirm the seat motor itself is functioning correctly.	A faulty motor can sometimes mimic the symptoms of a potentiometer issue.
Aftermarket Accessories	Aftermarket seat heaters or other modifications can interfere with the seat's electrical system.	Consider these modifications as a potential source of the problem.
Environmental Factors	Exposure to moisture or extreme temperatures can damage electrical components.	Protect the seat control system from environmental damage.
Diagnostic Flowchart	Use a diagnostic flowchart from the vehicle's service manual to guide the troubleshooting process.	A structured approach can help to identify the root cause of the problem more efficiently.

Detailed Explanations

Code Definition: The B1955 code specifically refers to an open circuit in the feedback loop of the seat's front up/down potentiometer. This means the seat control module is not receiving the expected signal from the potentiometer, indicating a break in the electrical circuit.

Potentiometer Function: A potentiometer is a variable resistor. In the context of a power seat, it changes its resistance as the seat moves up or down. This varying resistance translates into a varying voltage signal, which is sent to the seat control module. The module uses this information to determine the seat's precise position.

Circuit Components: The circuit consists of the potentiometer itself, the wiring harness connecting the potentiometer to the seat control module, the connectors at each end of the wiring, and the seat control module. Any of these components can fail, leading to an open circuit.

Common Causes: The most common causes include broken or damaged wires in the wiring harness, corroded or loose connectors, a faulty potentiometer (internally open circuit), and, less frequently, a damaged seat control module. Physical damage to the wiring is often caused by seat movement over time.

Symptoms: The primary symptom is the seat's inability to move up or down, or intermittent movement. In vehicles with memory seat functions, the system may be unable to save or recall seat positions. The B1955 DTC will also be present when scanned with a compatible scan tool.

Diagnostic Tools: A multimeter is essential for testing circuit continuity, voltage, and resistance. A scan tool is needed to read the DTC and clear it after the repair. Wiring diagrams are crucial for identifying the correct wires and connectors to test.

Diagnostic Procedure:

Visual Inspection: Start by visually inspecting the wiring harness and connectors for any obvious signs of damage, such as frayed wires, corrosion, or loose connections.
Circuit Testing: Use a multimeter to check for continuity in the wiring between the potentiometer and the seat control module. An open circuit will indicate a break in the wiring. Also check voltage at the potentiometer connector to confirm power and ground.
Potentiometer Testing: Disconnect the potentiometer and use a multimeter to measure its resistance. As you manually move the seat mechanism, the resistance should change smoothly and within the specifications outlined in the vehicle's service manual. If the resistance is infinite (open circuit) or does not change, the potentiometer is likely faulty.
Module Testing: If the wiring and potentiometer test good, the seat control module may be the issue. This requires specialized testing equipment or replacement with a known good module for testing purposes.

Repair Procedures:

Wiring Repair: If a broken wire is found, it can be repaired by splicing the wire back together and insulating the connection properly. Consider replacing the entire section of wiring if the damage is extensive.
Connector Cleaning/Replacement: Clean corroded connectors with electrical contact cleaner. If the connector is severely damaged, it should be replaced.
Potentiometer Replacement: If the potentiometer is faulty, it must be replaced. Ensure the replacement potentiometer is compatible with the vehicle.
Module Replacement: If the seat control module is faulty, it may need to be replaced and programmed.

Related DTCs: Other DTCs related to the seat system, such as B1954 (Seat Front Up/Down Potentiometer Circuit Short to Ground) or B1956 (Seat Front Up/Down Potentiometer Circuit Short to Battery), can indicate related issues within the seat control system. Addressing these codes in conjunction with B1955 may be necessary.

Affected Vehicle Systems: The power seat system is directly affected. The body control module (BCM) may also be involved, as it often communicates with the seat control module. The seat control module is the central component responsible for controlling the seat's movement.

Safety Precautions: Always disconnect the vehicle's battery before working on the electrical system. Be careful when working with electrical components to avoid electrical shock. Consult the vehicle's service manual for specific safety instructions.

Calibration/Programming Needs: After replacing the seat control module, it may need to be programmed or calibrated to the vehicle's specific configuration. This ensures that the module functions correctly with the other systems in the vehicle.

Wiring Harness Inspection: A thorough wiring harness inspection is crucial. Look for areas where the harness may be rubbing against the seat frame or other components, as this can lead to chafing and eventual wire breakage.

Connector Corrosion: Corrosion on the potentiometer and seat control module connectors can impede signal transmission. Clean the connectors with electrical contact cleaner and ensure they are securely fastened.

Potentiometer Resistance Range: The vehicle's service manual will specify the correct resistance range for the potentiometer. Use a multimeter to verify that the potentiometer's resistance falls within this range as the seat is moved.

Ground Circuit Integrity: A poor ground connection for the seat control module can cause a variety of electrical problems, including the B1955 code. Verify that the ground circuit is intact and providing a good ground connection.

Seat Motor Function: While diagnosing the B1955 code, confirm that the seat motor itself is functioning correctly. A faulty motor can sometimes mimic the symptoms of a potentiometer issue.

Aftermarket Accessories: Aftermarket seat heaters or other modifications can interfere with the seat's electrical system. Consider these modifications as a potential source of the problem. Disconnect them to test if they are causing the issue.

Environmental Factors: Exposure to moisture or extreme temperatures can damage electrical components. Protect the seat control system from environmental damage.

Diagnostic Flowchart: Using a diagnostic flowchart from the vehicle's service manual can help to guide the troubleshooting process. This structured approach can help to identify the root cause of the problem more efficiently.

Frequently Asked Questions

What does the B1955 code mean? The B1955 code indicates an open circuit in the feedback circuit of the seat's front up/down potentiometer. This means the seat control module is not receiving the expected signal.
What are the symptoms of a B1955 code? Common symptoms include the seat not moving up or down, intermittent seat movement, and the inability to save seat positions.
Can I fix the B1955 code myself? With the right tools, knowledge, and the vehicle's service manual, it is possible to diagnose and repair the issue yourself. However, if you are not comfortable working with electrical systems, it is best to consult a qualified technician.
What tools are needed to diagnose a B1955 code? A multimeter, scan tool, and wiring diagrams are essential for diagnosing the B1955 code.
How do I test the potentiometer? Disconnect the potentiometer and use a multimeter to measure its resistance. As you manually move the seat mechanism, the resistance should change smoothly and within the specifications outlined in the vehicle's service manual.

Conclusion

The B1955 DTC points to an open circuit within the front seat's height adjustment potentiometer feedback loop. A systematic diagnostic approach, including visual inspection, circuit testing, and component verification, is crucial for identifying and resolving the issue. Repairing or replacing faulty wiring, connectors, or the potentiometer itself will restore proper seat functionality.