C059100 - C059100 Brake Booster Motor Supply Current Low

C059100 Brake Booster Motor Supply Current Too Low - Fault Description Document

### Fault Depth Definition

The DTC C059100 is defined as "Brake Booster Motor Supply Current Too Low", where this code plays a core role in the safety monitoring logic of the Intelligent Power Braking System. This fault code reflects the ECU's real-time assessment results for actuator drive circuits. In automotive electrical and electronic architecture, the brake booster motor serves as a key executive component to increase pedal vacuum pressure or provide active assistive thrust; its supply current is an important physical quantity to judge load status. This fault indicates that the control unit (ECU/Controller) confirms through monitoring feedback loop that the actual current supplied to the motor has not reached the preset normal threshold range, which directly relates to the output stability of braking system assist force and the integrity of electronic hydraulic regulation function.

### Common Fault Symptoms

When the diagnostic system determines that this fault condition is met, the vehicle may exhibit the following perceivable operating characteristics:

• Intelligent Power Braking System Partial Function Failure: Drivers will perceive changes in brake pedal feedback characteristics or restrictions on active braking assist functions, leading to insufficient braking force output under emergency conditions.
• Instrument Panel Warning Lights On: A braking system fault indicator light (ABS/ESP or dedicated electronic brake light) may stay illuminated on the vehicle's central information display screen or dashboard, prompting the driver to check the system.
• Assist Response Delay: At the instant of startup or pressing the brake pedal, the motor drive signal may fail to establish a normal operating status, leading to an extended build-up time for assistance.
• System Enters Protection Mode: To ensure driving safety, control strategies may restrict maximum output current to prevent electrical overload, resulting in reduced actual braking torque.

### Core Fault Cause Analysis

According to diagnostic data mapping, this fault is primarily triggered by potential abnormalities in the following three dimensions:

1. Hardware Components (Power Protection Devices): The most direct hardware failure form is a blown fuse. This usually means there is a short circuit risk at the rear of the circuit or a current peak exceeding the melting body design capacity, causing the main power supply loop to physically disconnect.
2. Wiring and Connectors (Physical Connection Layer): Wiring harness or connector fault is the main reason for abnormal increase in resistance. This may manifest as pin withdrawal from plugs, contact terminal corrosion, wire insulation layer damage grounding, or virtual connection inside connectors, leading to attenuation of effective current transmitted to motor ports.
3. Controller Unit (Logic Operation and Drive Level): Intelligent Power Brake Controller Internal Fault involves damage to control strategy chips or power drive level electronic components. If there is a deviation in the sampling circuit inside the controller, even if the motor supplies power normally, its internal algorithm may incorrectly calculate "current too low", which belongs to false reporting or hardware aging at the controller self-check logic level.

### Technical Monitoring and Trigger Logic

The setting of this fault code follows strict temporal logic and electrical parameter determination rules:

• Monitoring Target: The system continuously monitors brake booster motor supply current. This parameter needs real-time collection for comparison against standard curves to ensure the motor can obtain sufficient power support in an activated state.
• Numerical Judgment Range: When the actual collected current value is lower than the controller calibration threshold (defined as too low), the judgment logic is triggered. Fault determination does not rely on fixed voltage values but on the integrity of the current signal.
• Specific Operating Conditions Requirement: This monitoring is valid only when the start switch is placed in ON gear. The control unit begins collecting data after power-on self-check or entering running mode; low current signals are only marked as a fault code when ignition power is connected and the system is in an active state. If the vehicle is turned off, the monitoring program pauses, and such records will not be generated.
• Trigger Condition Explanation: Once it is confirmed that the supply current continuously falls below the expected baseline, the system generates C059100 fault code and turns on the corresponding indicator light to maintain the vehicle's safety redundancy status.