AU
C051600

DTC C051600 indicates the IPB (Intelligent Integrated Braking System) detects an intermittent abnormality or insufficient plausibility in the right rear wheel speed sensor signal — Seal U

Braking System

DTC C051600 indicates the IPB (Intelligent Integrated Braking System) detects an intermittent abnormality or insufficient plausibility in the right rear wheel speed sensor signal.

Unlike a direct open or short circuit fault, 'indirect uncertainty' means the sensor still returns a signal, but under specific operating conditions (such as a specific vehicle speed range, steering maneuver, or road input), the signal spikes, drifts, or illogically contrasts with the other wheel signals.

The IPB system algorithm compares the four-wheel speed differential, longitudinal acceleration, and yaw rate signals.

The system triggers this fault when the right rear wheel speed signal duration or amplitude exceeds the plausible confidence interval but has not yet reached the hard fault threshold.

This condition typically indicates dynamic sensor-to-tone ring gap variation, electromagnetic signal interference, or an intermittent voltage drop in the sensor power supply or ground, which can cause ABS/ESC function degradation or false activation.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Ferromagnetic debris or brake dust adhering to the right rear wheel speed sensor tip changes the air gap effective magnetic permeability, causing unstable signal amplitude.
  • 2Right rear wheel hub bearing wear causes axial/radial play to exceed tolerance, dynamically changing the relative position between the sensor and tone ring (common on vehicles with mileage > 50,000 km).
  • 3Repeated bending of the sensor wiring harness in the transition area between the body and rear wheel (such as inside the sill trim panel or near the rear suspension) causes hidden breaks in the internal wires, resulting in intermittent increases in contact resistance.
  • 4Scratches, deformation, or localized missing teeth on the surface of the right rear wheel speed sensor tone ring (magnetic ring) cause abnormal Hall signal pulses.
  • 5Performance drift in the sampling resistor or filter capacitor of the IPB system internal signal processing circuit for the right rear wheel speed channel causes an abnormal signal interpretation threshold.
What To Do
  • 1
    Connect the VDS diagnostic tool, enter the IPB system, and read the live data stream. Monitor the right rear wheel speed signal for erratic fluctuations, negative values, or a difference >3 km/h compared to the other three wheels during stationary, accelerating, constant speed, and steering conditions.
  • 2
    Raise the vehicle. Visually check if the right rear wheel speed sensor is loose in its mounting hole, and inspect the sensor head for oil or metal swarf. Clean the sensor end face and use a feeler gauge to measure the clearance to the tone ring (standard: 0.3-1.2 mm; Song PLUS DMi standard value: approximately 0.8 mm).
  • 3
    Disconnect the IPB wiring harness from the right rear wheel speed sensor connector. Measure the resistance on the sensor side (magnetic type: approx. 1.0–1.5 kΩ; Hall type: supply power and measure the signal voltage). Measure the harness continuity, focusing on the resistance stability from the main body harness to the wheel end while bending the harness.
  • 4
    Check the right rear wheel hub bearing axial play: Hold the tyre at the 6 o'clock and 12 o'clock positions with both hands. Push and pull to check for obvious free play. If the play is >0.5 mm, replace the wheel hub bearing assembly to restore sensor air gap stability.
  • 5
    If the hardware check reveals no faults, upgrade the IPB system software (some early Song PLUS DMi versions have a wheel speed signal filtering algorithm defect and require an upgrade to V2.5 or later) and complete the zero-point calibration for the yaw rate sensor and wheel speed sensors.
  • 6
    Clear the fault code and perform a road test. Verify right rear wheel speed signal continuity under ABS activation conditions (such as braking on a low-traction surface). Confirm the fault code does not recur before returning the vehicle.
Real-World Cases
BYD DTC AI Analysis

Iron filings contaminated the right rear wheel speed sensor, causing intermittent signal loss.

✓
A 2021 Song PLUS DMi with 42,000 km developed an intermittent ABS warning light; the fault occurred more frequently after high-speed driving over speed bumps. Diagnosis revealed history fault C051600; live data showed the right rear wheel speed intermittently dropping to zero around 60 km/h. Inspection found the sensor head heavily contaminated with brake dust and metal debris from worn right rear brake pads. Cleaning restored normal gap measurements, but magnetic contamination had compromised the Hall element. Replacing the right rear wheel speed sensor (Part No.: 3630100-XX) resolved the fault.
BYD DTC AI Analysis

Concealed open circuit in boot wiring harness at flex point

✓
After driving through water, the right rear wheel speed signal became intermittent, with DTCs C051600 and C051100 (right front wheel) appearing simultaneously. Inspection revealed the vehicle had been fitted with aftermarket parking sensors; the wiring harness routed through the right rear sill compromised the factory waterproofing. Focused inspection of the body-to-rear-door transition harness found the right rear wheel speed sensor signal wire had strands broken but not completely severed inside the rubber boot. Resistance jumped between 0.5–5 Ω when flexing the harness. Repaired the harness and resealed the waterproofing. Fault resolved.
BYD DTC AI Analysis

Worn wheel hub bearing caused dynamic air gap to exceed tolerance

✓
2022 Song PLUS DMi at 80,000 km. DTC C051600 only triggered when turning right at 40-60 km/h. Live data showed the right rear wheel speed dropped 5-8 km/h below the other wheels during these events. Inspection found the right rear wheel hub bearing had developed 0.8 mm radial play (standard <0.3 mm). When turning right, body roll changed the tyre camber angle, causing the gap between the sensor and tone ring to momentarily exceed the Hall sensor's effective detection range. Replaced the wheel hub bearing assembly (including tone ring); the fault has not recurred.
BYD DTC AI Analysis

IPB system software false positive (phantom fault)

✓
New vehicle, 2000 km. ESC warning light triggered after high-speed driving in wet conditions, storing DTC C051600. Checked sensors, wiring harness and tone rings—found no physical damage. All four wheel speed signals normal under static and dynamic conditions. TSB indicates this batch of IPB controllers (version V1.8) has an overly sensitive filtering algorithm when wheel speed signals fluctuate rapidly (e.g., sudden tyre slip rate changes after driving through water), causing false intermittent faults. Upgraded IPB software to version V2.6 and flashed calibration data. Resolved.
BYD DTC AI Analysis

Heat-warped tone ring causes erratic signal when hot

✓
Vehicle started normally from cold. Dashboard warning triggered after one hour of continuous driving. With the vehicle hot, live data showed periodic fluctuation in the right rear wheel speed signal (synchronised with tyre rotation). After cooling, inspection found localised heat discolouration on the tone ring from previous brake dragging. Thermal expansion caused the tone ring to exceed out-of-roundness tolerance. Replaced the right rear brake disc (with integrated tone ring) and fixed the brake caliper return issue. Fault eliminated.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.