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) — 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.

The C051000 fault code on the Seal U indicates a high-severity short to battery in the left rear wheel speed sensor power supply circuit. This can disrupt ABS, ESC, EBD, and AEB functions. Common causes include damaged sensor wiring near the rear suspension or an internal short in the wheel speed sensor. Stop driving if warning lights appear and visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged left rear wheel speed sensor wiring harness insulation, especially in the corrugated conduit section passing between the body and suspension, shorting to an adjacent 12V power wire (such as the tail light power wire or fuel pump power wire).
  • 2Breakdown of the wheel speed sensor internal Hall element or capacitor abnormally lowers impedance between the power supply and signal pins, causing an internal short circuit.
  • 3IPB control unit internal power regulation module (LDO or DC-DC) fault, shorting 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 (usually located near the steering knuckle) seal fails, and conductive fluid creates a short-circuit path between the terminals.
  • 5After chassis bottoming out or accident repairs, wiring harness retaining clips loosen, causing the harness to rub against high-temperature or moving parts such as the exhaust pipe or suspension brackets. The damaged insulation then shorts to a constant power 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 if the fault is static (sets the code at key ON) or dynamic (sets the code at a specific vehicle speed).
  • 2
    Raise the vehicle and remove the left rear tyre. Visually inspect the entire wheel speed sensor wiring harness. Focus on the corrugated conduit entry and exit points, body sheet metal pass-throughs, and the area near the rear differential. Check for signs of harness abrasion, scorching, or discolouration.
  • 3
    Disconnect the connectors for the IPB control unit (located near the engine compartment firewall) and the left rear wheel speed sensor. 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 10Ω, a short to power exists; 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 separately measure the continuity of the front and rear harness sections to pinpoint the short circuit location.
  • 5
    Measure sensor body resistance: Normal Hall-effect sensor resistance is 1.5-2.5 kΩ. If the reading is below 1 kΩ or shows continuity, replace the left rear wheel speed sensor (requires a BYD-specific Hall 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 reading shows 12-14V battery voltage instead of the standard 5V reference voltage, diagnose an internal IPB fault and replace the integrated intelligent braking system assembly (use a dedicated diagnostic tool for programming and matching).
  • 7
    Repair the wiring harness: insulate damaged sections with double-layer heat-shrink tubing; replace the entire wiring harness if necessary. Restore the connector seal and apply an appropriate amount of conductive paste (not insulating silicone grease). Securely fasten the wiring harness and maintain a distance 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 Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.