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C051000

DTC C051000 indicates the IPB (Integrated Intelligent Braking System) detected an abnormally low-resistance path between the left rear wheel speed sensor power supply circuit (typically a 5V or 12V reference voltage) and the vehicle main power supply (B+, battery voltage) — Seal U

Braking System

DTC C051000 indicates the IPB (Integrated Intelligent Braking System) detected an abnormally low-resistance path between the left rear wheel speed sensor power supply circuit (typically a 5V or 12V reference voltage) and the vehicle main power supply (B+, battery voltage).

In automotive electronic diagnostics, "Short to Battery" means the signal wire or power supply wire shorted to the positive 12V power supply.

This fault causes the sensor supply voltage to rise abnormally above the rated 5V/12V to the 13-14V battery voltage range, triggering the overvoltage protection mechanism in the IPB control unit.

Because the wheel speed signal is a core input parameter for the ABS, ESC, EBD, and Autonomous Emergency Braking (AEB) systems, this fault causes these safety systems to enter a degraded mode or fail completely, posing a severe driving safety hazard.

Potential causes include physical damage to the wiring harness, electronic component breakdown inside the sensor, water ingress and corrosion in the connector, or a power management chip failure inside the IPB control unit.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i Multiple System Warnings After Water Ingress — Repair Case

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A 2021 Song PLUS DM-i with 23,000 km. The owner reported that after driving through standing water during a heavy rainstorm, the dashboard simultaneously lit the ABS, ESP, tire pressure, and automatic emergency braking warning lights. A VDS scan pulled codes C051000 (left rear wheel speed sensor supply circuit short to battery) and C051500 (left rear wheel speed sensor fault). Inspection found obvious water staining and copper oxide inside the left rear wheel harness connector (located above the steering knuckle), with insulation resistance between terminals at just 0.8 Ω. Taking the connector apart revealed the seal ring had degraded and was missing, letting rainwater in. Fix: Cleaned the terminals thoroughly with electronic cleaner, replaced the waterproof connector assembly, re-wrapped the harness, and added sealant. No recurrence after 3 months of follow-up.
BYD DTC AI Analysis

Wiring harness chafed through and shorted to tail light power wire

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2022 Song Pro DM, 48,000 km. Owner reported the instrument cluster occasionally showed brake system fault warnings during hard braking. Historical DTCs showed intermittent C051000. Inspection found the left rear wheel speed sensor harness retaining clip had come loose where it passes through the sheet metal hole between the C-pillar and rear fender, letting the harness rub against the rear taillight 12V power harness. The insulation wore through, exposing the copper and creating an intermittent short. Bumpy roads or body twist triggered the fault. Repaired the damaged harness section (~15 cm) with double-layer heat shrink tubing, re-secured the routing, fitted an abrasion protection sleeve, and ensured 50 mm+ separation from the power harness.
BYD DTC AI Analysis

IPB Control Unit Internal Power Module Failure Case

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2021 Song Plus EV. After accident repairs (rear bumper and left rear suspension replacement), DTC C051000 persisted and would not clear. Replaced left rear wheel speed sensor and harness; fault remained. Measured 13.2V at IPB control unit output terminal to ground (abnormal). Disconnected external harness; control unit no-load output still showed battery voltage. Diagnosis: IPB internal 5V regulator module breakdown. Root cause: battery not disconnected during repairs; surge current from welding rear suspension damaged IPB. Solution: Replaced IPB integrated intelligent braking system assembly, performed online coding and ESC calibration, and executed zero-point calibration of longitudinal and lateral acceleration sensors.
BYD DTC AI Analysis

Sensor internal breakdown causing short circuit

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Song MAX DM-i, 60,000 km. ABS warning light stayed on during service. Diagnostic tool showed C051000. Left rear wheel speed sensor supply voltage measured 12.4V (should be 5V). Disconnected the sensor plug; harness side measured 5V, confirming an internal short. Disassembled the faulty sensor and found obvious burn marks on the Hall chip from electrical breakdown. Traced the cause to previous use of a non-genuine jack under the left rear suspension, likely causing mechanical shock to the sensor. Replaced with a genuine wheel speed sensor (installation torque 8±2Nm, tone ring air gap 0.8mm). Fault cleared.
BYD DTC AI Analysis

Aftermarket reversing sensors causing power supply crosstalk

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BYD Song Plus DM-i 2021. Owner installed aftermarket reversing sensors, tapping into the left rear tail light circuit for power. One week later the instrument cluster displayed a braking system fault; scan read DTC C051000. Inspection found the modified wiring had loose insulation tape. The 12V supply line for the reversing sensors rubbed against the wheel speed sensor harness inside the C-pillar, causing intermittent shorts over bumps. More critically, the modification drew unfused direct power, creating a fire hazard. Repair: Removed the non-compliant wiring, restored original harness routing, repaired insulation damage on the wheel speed sensor harness, and advised the owner to use BYD genuine accessories or professional shops for future installations.
Other Seal U Fault Codes
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.