U01EF87 - U01EF87 SWS Signal Invalid (SWS Signal Value Invalid Fault)

meaning the receiver cannot parse a physical location or operation command data flow conforming to logical definitions. This definition not only points to single signal loss but also covers data integrity check failures, i.e., under preset voltage and communication protocols, the control unit cannot confirm that commands sent by steering wheel switches are in an effective working window. The appearance of U01EF87 indicates that input data received by the controller from the SWS port exceeds the predefined logical value range or signal quality does not meet system thresholds.

Common Fault Symptoms

When this fault code is recorded and trigger conditions are met, drivers may perceive the following system status abnormalities:

• Multi-Function Video Controller Function Failure: Multimedia control originally integrated on the steering wheel, volume adjustment, or voice command response function modules may become unable to execute or enter sleep state.
• Steering Wheel Switch Signal Interruption: The instrument cluster or central screen may no longer display operation feedback from steering wheel buttons, such as phone answer confirmation or cruise control status update stagnation.
• Vehicle Auxiliary Feature Limitation: Driving assistance systems involving SWS signals (such as temporary setting of adaptive cruise) may enter conservative mode, prompting function unavailability but vehicle power not affected.

Core Fault Cause Analysis

Based on logical deduction from existing data, the formation of U01EF87 mainly stems from abnormalities in the following three technical dimensions:

• Hardware Component Dimension (Steering Wheel Switch): Multi-function buttons on the steering wheel themselves have poor contact, internal wiring breakage, or unstable signal source chip operation, leading to inability to generate effective pulse signals.
• Wiring and Connector Dimension: The physical link between MFVC controller and steering wheel switch may experience excessive impedance, ground short circuit, or power short circuit, causing voltage drop or interference during signal transmission process.
• Controller Logic Dimension (MFVC/ECU): Signal processing module inside the control unit failed to correctly identify timing or amplitude of input signals, leading to logical operation level judgment that this data stream is "Invalid Value", even if hardware is not damaged, may report code due to parameter configuration mismatch.

Technical Monitoring and Trigger Logic

Fault monitoring algorithms strictly follow specific electrical environments and time windows for determination. Specific trigger logic includes the following hard indicators:

• Electrical Environment Constraint: Detection only takes effect when controller supply voltage is within a specific range, i.e., $9V$~$16V$. Below this lower limit or exceeding this upper limit will pause detection requests for this DTC to avoid low-battery noise interference.
• Initialization Time Window: System needs at least $3s$ after power-on completion initialization before starting monitoring, ensuring internal Self-Test process has ended and entering dynamic work mode.
• Operation Status Dependency: Start switch must be in ON position, vehicle is in powered run or D/S/N/R gear activated state.
• Communication Network Status: Public CAN not entered busoff status, meaning underlying communication link remains connected and possesses data sending capability, excluding signal loss caused by total line routing paralysis.
• Re-enable Protection: If ECU was in Re-enable stage of DTC detection request, system will lock fault code generation logic within subsequent $3s$ to prevent repeated reporting due to instantaneous interference.

Cause Analysis Based on logical deduction from existing data, the formation of U01EF87 mainly stems from abnormalities in the following three technical dimensions:

• Hardware Component Dimension (Steering Wheel Switch): Multi-function buttons on the steering wheel themselves have poor contact, internal wiring breakage, or unstable signal source chip operation, leading to inability to generate effective pulse signals.
• Wiring and Connector Dimension: The physical link between MFVC controller and steering wheel switch may experience excessive impedance, ground short circuit, or power short circuit, causing voltage drop or interference during signal transmission process.
• Controller Logic Dimension (MFVC/ECU): Signal processing module inside the control unit failed to correctly identify timing or amplitude of input signals, leading to logical operation level judgment that this data stream is "Invalid Value", even if hardware is not damaged, may report code due to parameter configuration mismatch.

Technical Monitoring and Trigger Logic

Fault monitoring algorithms strictly follow specific electrical environments and time windows for determination. Specific trigger logic includes the following hard indicators:

• Electrical Environment Constraint: Detection only takes effect when controller supply voltage is within a specific range, i.e., $9V$~$16V$. Below this lower limit or exceeding this upper limit will pause detection requests for this DTC to avoid low-battery noise interference.
• Initialization Time Window: System needs at least $3s$ after power-on completion initialization before starting monitoring, ensuring internal Self-Test process has ended and entering dynamic work mode.
• Operation Status Dependency: Start switch must be in ON position, vehicle is in powered run or D/S/N/R gear activated state.
• Communication Network Status: Public CAN not entered busoff status, meaning underlying communication link remains connected and possesses data sending capability, excluding signal loss caused by total line routing paralysis.
• Re-enable Protection: If ECU was in Re-enable stage of DTC detection request, system will lock fault code generation logic within subsequent $3s$ to prevent repeated reporting due to instantaneous interference.