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B16E300

DTC B16E300 indicates a current monitoring anomaly or communication error in the Electronic Parking Brake (EPB) left rear wheel actuator (motor) — Seal U

Safety System

DTC B16E300 indicates a current monitoring anomaly or communication error in the Electronic Parking Brake (EPB) left rear wheel actuator (motor).

The EPB control module sets this fault when it detects the left rear parking motor operating current exceeds the calibrated threshold (normal range approximately 8-15 A) or fails to establish valid communication with the left rear motor.

Possible causes include an internal motor short or open circuit, mechanical binding, poor wiring connections, or a control module fault.

When this fault triggers, the system enters a safety protection mode.

This mode may prevent the electronic parking brake from releasing or applying, disable the Auto Hold function, and illuminate an instrument cluster warning.

Extreme cases immobilize the vehicle or create a rollaway risk.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Excessive wear of the internal carbon brushes or commutator ablation in the left rear EPB motor abnormally increases contact resistance, causing the operating current to deviate from the standard value.
  • 2Oxidation, corrosion from water ingress, or backed-out pins at the motor wiring harness connector, causing excessive contact resistance or interrupted signal transmission.
  • 3Mechanical binding or incomplete return of the left rear brake caliper causes excessive motor load and triggers overcurrent protection.
  • 4Chassis wiring harness chafes against body or suspension components, damaging the insulation and causing an intermittent short or open circuit.
  • 5Outdated EPB control module software or a hardware fault in the current monitoring circuit triggers a false code.
What To Do
  • 1
    Use the VDS2000/VDS3.0 diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether B16E300 is a current or history fault, and record the specific abnormal current monitoring values.
  • 2
    Raise the vehicle and visually inspect the condition of the left rear wheel EPB motor wiring harness connector. Check the sealing ring for aging. Measure the supply voltage at the connector (should be 12V constant power) and verify proper ground.
  • 3
    Disconnect the connector and measure the static resistance of the left rear EPB motor (normal value: 0.8-1.2 Ω). Compare it with the right rear wheel. Perform an actuation test and check the motor for smooth operation, abnormal noise, or binding.
  • 4
    Inspect the wiring harness routing along the chassis, focusing on interference points with the rear suspension and body. Check the corrugated conduit for damage. Repair any damaged wiring and re-secure the harness routing.
  • 5
    If motor resistance is abnormal, operation binds, or internal water ingress is present, replace the left rear electronic parking brake assembly (including motor). If the fault is limited to the wiring harness, repair the wiring harness and apply conductive paste.
  • 6
    After replacement or repair, use the diagnostic tool to perform the EPB system initialization procedure, including "Parking Brake Bedding-in", "Clearance Self-learning", and "Current Calibration".
  • 7
    Clear the fault code and perform a road test: test the parking brake apply/release and Auto Hold activation/deactivation functions on level ground and slopes, and confirm the left and right wheel motor operating currents are consistent (12-13A).
Real-World Cases
BYD DTC AI Analysis

BYD Han EV electronic parking brake system intermittent failure

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Symptoms: Instrument cluster intermittently displayed "Check Electronic Parking System" warning. Electronic parking brake failed intermittently. Diagnosis: VDS read code B16E300 (Left Motor Current Monitoring Circuit Abnormal). EPB control unit power supply: normal. Found oxidation and corrosion inside the left parking brake motor wiring harness connector. Motor resistance measured 1.2Ω (above normal). Determined a slight internal short circuit in the motor. Solution: Replaced the left parking brake motor assembly. Cleaned the wiring harness connector and applied conductive grease. Performed the EPB initialisation calibration procedure. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM electronic parking brake system fault, vehicle unable to drive

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Symptoms: While driving, the dashboard displayed "Electronic Parking System Fault". After parking, the electronic handbrake would not release and the vehicle could not move. Diagnosis: Read DTCs B16E300 (Left Rear EPB Motor Current Abnormal) and C100601 (CAN Signal Timeout). The left rear EPB motor supply voltage measured 12.4V (normal), but the motor did not respond during actuator testing. Disassembly found the motor waterproof sealing ring had perished, allowing rainwater ingress that seized the motor and caused current draw to exceed the threshold. Solution: Replaced the left rear electronic parking brake assembly (including motor), replaced the waterproof sealing ring, updated the control module software, and cleared the fault codes. Road test normal.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro EV electronic parking brake malfunction after driving in rain

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Symptoms: After driving in rain, at the next day's start-up the electronic parking brake (EPB) warning light stayed on. Releasing the parking brake required multiple attempts, with an audible alarm sounding. Diagnosis: Retrieved DTC B16E300 (Left EPB Actuator Current Monitoring Fault). Inspection found the left rear wheel speed sensor harness and the EPB motor harness had chafed through their insulation at the underbody, with rainwater causing an intermittent short circuit. Measured motor stall current: 18 A (normal: below 15 A). Repair: Repaired the damaged wires, re-secured the harness routing, added corrugated tubing for protection, and replaced the left EPB motor (worn from sustained overload). Fault cleared after system calibration.
Original source ↗
BYD DTC AI Analysis

BYD Seal Auto Hold failure when parking on a slope.

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Symptoms: After parking on a slope, the electronic parking brake auto-apply function failed, requiring manual button operation. No warning light appeared on the instrument cluster, but the system stored fault codes. Diagnosis: VDS3.0 retrieved historic fault code B16E300, pinpointing the left rear EPB motor current monitoring circuit. Simulated slope load testing revealed abnormal motor operating current fluctuation (10-16A). Disassembling the motor exposed severely worn carbon brushes and burnt commutator surfaces; increased contact resistance caused current monitoring values to exceed limits. Resolution: Replaced the genuine left rear electronic parking brake motor and performed the 'parking brake bedding-in' and 'clearance self-learning' procedures. The automatic parking brake function returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Yuan Plus electronic parking brake abnormal noise after collision repair

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Symptoms: After collision repairs replacing the rear bumper and left rear knuckle, the electronic parking brake released slowly and made abnormal noise, and the instrument cluster displayed a "Check Parking System" warning. Diagnosis: Scanning showed codes B16E300 (Left Motor Current Abnormal) and B16E400 (Right Motor Current Abnormal). Inspection found the left rear EPB motor connector had not been fully seated during the collision repairs, with terminals backed out. The newly fitted left rear brake caliper also had a seized motor connection mechanism, causing the left motor to sustain a current draw of 17A (excessive). Solution: Repaired the harness connector and replaced the left rear brake caliper assembly (internal mechanism deformed). Performed current calibration and position learning on both EPB motors. After clearing the fault codes, current tested normal at 12-13A.
Original source ↗
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.