AU
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) — Atto 8

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.

The C051000 fault code on the Atto 8 indicates a short to battery in the left rear wheel speed sensor power supply circuit. Severity is high because it can affect ABS, ESC, EBD, and AEB operation. Common causes include damaged sensor wiring insulation or an internal wheel speed sensor short. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Damaged left rear wheel speed sensor wiring harness insulation, particularly in the corrugated conduit section routed between the body and suspension, shorting to an adjacent 12V power wire (such as the tail light or fuel pump power wire).
  • 2Wheel speed sensor internal Hall element or capacitor breakdown causes abnormally low impedance between the power supply and signal pins, creating an internal short circuit.
  • 3Faulty IPB control unit internal voltage regulation module (LDO or DC-DC) shorts the power supply output terminal directly to the internal battery power supply.
  • 4After vehicle wading or high-pressure washing, the left rear wheel wiring harness connector seal (usually located near the steering knuckle) fails, allowing conductive electrolyte to create a short-circuit path between the terminals.
  • 5After chassis bottoming out or accident repairs, loose wiring harness retaining clips cause the harness to rub against high-temperature or moving parts, such as the exhaust pipe or suspension bracket, damaging the insulation and shorting to a constant live circuit.
What To Do
  • 1
    Use the VDS2000 or VDS3000 diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, throttle opening, and ambient temperature when the fault occurred. Confirm whether the fault is static (code sets at key ON) or dynamic (code sets at a specific vehicle speed).
  • 2
    Raise the vehicle and remove the left rear tyre. Visually inspect the entire wheel speed sensor wiring harness, focusing on the corrugated conduit entry and exit points, the body sheet metal pass-throughs, and the area near the rear differential. Check for signs of harness abrasion, scorching, or discolouration.
  • 3
    Disconnect the IPB control unit (located near the engine compartment firewall) and left rear wheel speed sensor connectors. Use a multimeter to measure the resistance between the sensor power supply pin (usually pin 1) and body ground: if the resistance is less than 10 Ω, this confirms a short to power; if infinite, suspect an internal control unit fault.
  • 4
    Section-by-section troubleshooting: Locate the left rear wheel wiring harness intermediate connector (usually inside the C-pillar trim panel or under the rear seat). Disconnect the connector and measure the continuity of the front and rear wiring harness sections separately to pinpoint the short circuit location.
  • 5
    Measure the sensor body resistance: normal Hall-effect sensor resistance is 1.5-2.5 kΩ. If the measured value is below 1 kΩ or shows continuity, replace the left rear wheel speed sensor (use a BYD-specific Hall-effect sensor and verify the tone ring air gap is 0.3-1.2 mm).
  • 6
    If the wiring harness and sensor are normal, measure the output voltage at the corresponding pin of the IPB control unit. With the key in the ON position, if the pin outputs a 12-14V battery voltage instead of the standard 5V reference voltage, this indicates an internal IPB fault. Replace the Integrated Intelligent Braking System assembly (use a dedicated diagnostic tool for programming and matching).
  • 7
    Repair the wiring harness: insulate damaged sections using double-layer heat-shrink tubing, or replace the entire wiring harness if necessary. Restore the connector seal and apply an appropriate amount of conductive paste (not insulating silicone grease). Secure the wiring harness and maintain a clearance of at least 150 mm from high-temperature components.
  • 8
    Clear the fault code and perform dynamic self-learning: drive in a straight line at 20-40 km/h and observe the diagnostic tool data stream to verify the left rear wheel speed signal synchronizes with the other three wheels; perform the ABS/ESC dynamic test to confirm normal system operation.
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 Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.