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 3

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 3 indicates a short to battery in the left rear wheel speed sensor power supply circuit, causing abnormal voltage to the IPB braking control system. Severity is high because ABS, ESC, EBD, and AEB may be reduced or disabled. Common causes include damaged sensor wiring insulation or an internal sensor short. 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 3
  • 1Damaged left rear wheel speed sensor harness insulation, especially in the corrugated conduit between the body and suspension, shorting to an adjacent 12V power wire (such as the tail light or fuel pump power wire).
  • 2Breakdown of the internal Hall element or capacitor in the wheel speed sensor abnormally reduces impedance between the power supply and signal pins, creating an internal short circuit.
  • 3Internal power regulator module (LDO or DC-DC) failure in the IPB control unit, shorting the power supply output terminal directly to the internal battery power supply.
  • 4After driving through water or high-pressure washing, the left rear wheel wiring harness connector seal (usually located near the steering knuckle) fails, allowing conductive electrolyte to form a short circuit 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. Damaged insulation then shorts 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 at the time of the fault. Confirm whether it is a static fault (code sets at ignition ON) or a dynamic fault (code sets at a specific vehicle speed).
  • 2
    Raise the vehicle and remove the left rear tyre. Visually inspect the entire length of the wheel speed sensor wiring harness. Focus on the corrugated conduit entry and exit points, body panel pass-throughs, and the area near the rear differential. Look 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, the fault may be internal to the control unit.
  • 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 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 (typically a BYD-specific Hall-effect sensor; 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 ignition ON, 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 areas with double-layer heat-shrink tubing; replace the entire harness section if necessary. Restore the connector seal and apply an appropriate amount of conductive paste (not insulating silicone grease). Fasten the wiring harness securely and maintain a minimum clearance of 150mm 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 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 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.