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P056216

P056216 is a BYD IPB (Intelligent Power Brake) extended fault code — Seal 6 EV

Braking System

P056216 is a BYD IPB (Intelligent Power Brake) extended fault code.

It indicates the IPB control module detects its supply voltage remaining continuously below the internal threshold (typically 9V-10V; normal operating voltage is 12V±0.5V).

As the core brake-by-wire component, the IPB provides electro-hydraulic brake assist, coordinates energy recovery, and controls ESC and ABS functions.

Insufficient supply voltage reduces brake assist motor torque, causing a stiff brake pedal and extended braking distances.

This condition can also degrade or deactivate ESC and ABS functions, severely compromising driving safety.

This fault code typically triggers the IPB warning light, the ABS warning light, and a "Please check the braking system" message.

The P056216 fault code on the Seal 6 EV indicates the IPB brake control module is seeing supply voltage stay too low, usually below 9–10V. Severity is medium because brake assist may be reduced, with possible ABS or ESC warnings. Common causes include an aging or discharged 12V battery, or poor contact in the IPB power supply circuit. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Low-voltage battery aging or depletion: The 12V battery used in BYD hybrid/pure electric models (mostly AGM or EFB type) reaches the end of its service life or experiences deep discharge, causing voltage to drop below 9V during cold starts or high electrical loads.
  • 2Poor contact in the IPB power supply circuit: Backed-out terminals or loose connections at the power supply connector from the front compartment power distribution box to the IPB module (usually located near the firewall), or fuse holder oxidation increasing contact resistance and causing a voltage drop.
  • 3Front compartment power distribution box internal fault: Burnt relay contacts or a broken internal copper busbar inside the distribution box cause unstable output voltage at the IPB power supply terminal.
  • 4Poor earth point: IPB module earth point (usually G301, G302, or left front chassis rail earth point) is loose, oxidised, or has residual paint, increasing circuit resistance.
  • 5DC-DC converter fault (new energy vehicles): The on-board DC-DC converter produces an abnormal output when converting high voltage to 12V low voltage, or the low-voltage charging strategy fails, causing the system voltage to remain continuously low.
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS or a dedicated diagnostic tool to read the fault code. View the freeze frame data and note the specific voltage value when the fault occurred (e.g., Battery Voltage: 8.2V). Confirm conditions such as vehicle speed and mileage at the time of the fault to distinguish between a static battery discharge and a dynamic power supply fault.
  • 2
    Low-voltage battery condition check: Measure the battery static voltage (should be ≥12.4V), perform an internal resistance test (CCA value should be ≥70% of the rated value), and check the battery terminals for oxidation or looseness. If the voltage is below 12V or the internal resistance is too high, replace with a genuine AGM battery first.
  • 3
    IPB power supply circuit static inspection: Inspect the IPB-related fuses in the front compartment power distribution box (usually F4/9, F4/10, or 30A/40A fuses marked "IPB" or "ESC") for blown elements or oxidation. Inspect the IPB wiring harness connectors (connector A is a large 26-pin connector, connector B is a small 12-pin connector) for backed-out pins and signs of water ingress or corrosion.
  • 4
    Dynamic voltage measurement: Turn the key to the ON position (do not press the brake pedal). Use a multimeter to measure the voltage to ground at IPB connector pin 1 (constant power 30) and pin 14 (ignition power 15). Voltage should be ≥11.5V. Measure the voltage drop between the IPB ground point (usually connected to the left front chassis rail) and the battery negative terminal. Voltage drop should be ＜0.1V. An excessive voltage drop indicates high circuit resistance.
  • 5
    Power distribution box output test: If the power distribution box input voltage is normal (battery voltage) but the output voltage to the IPB is low, disassemble the power distribution box and inspect the internal relay contacts for burning. Replace the front compartment power distribution box assembly if necessary.
  • 6
    Clean and tighten the ground points: Remove the IPB ground points (G301/G302). Sand the contact surfaces to bare metal. Apply conductive grease and tighten to the standard torque (usually 8-10 N·m). Check the body ground stud for stripped threads.
  • 7
    DC-DC function verification (new energy vehicles): With the vehicle in READY mode, measure the charging voltage across the battery terminals. The voltage must be 13.8V-14.5V. If the voltage remains below 13V, check the DC-DC low-voltage output circuit. If necessary, flash the DC-DC control software or replace the DC-DC assembly.
  • 8
    Fault repair and function verification: After repairing or replacing the faulty component, clear the fault codes and perform the IPB system bleeding procedure (use a diagnostic tool to execute the "Electro-hydraulic Brake System Bleeding" process). Road test the vehicle to confirm normal brake pedal effort and no illuminated warning lights. Read the fault codes again to confirm P056216 does not return.
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i IPB power supply connector pin backed out causing intermittent brake fault

✓
While driving, the instrument cluster intermittently displayed "Brake System Fault". Both the IPB and ABS warning lights came on together and the brake pedal went hard. Scanned with a diagnostic tool and retrieved codes P056216 (System Voltage Low) and C123456 (IPB Power Supply Abnormal). Freeze frame data showed 8.1V at the time of the fault. Measured voltage at IPB connector pin A-1 (constant power) and found it swinging between 8V-12V while wiggling the wiring harness. Disassembled the IPB connector and found pin 1 (thick red wire) had backed out—the internal latch had broken, allowing the pin to retract. Fix: Used a special pin removal tool to re-crimp the pin. Replaced the IPB wiring harness connector (Part No.: GJ-XXX-XXXX) and seated the pin fully. Voltage stabilized and the fault cleared.
Original source ↗
BYD DTC AI Analysis

Burnt relay contacts inside the front compartment power distribution box caused IPB undervoltage

✓
After parking overnight, the owner reported a brake system fault and DTC P056216 on morning startup; the warning light cleared after driving. The low voltage battery voltage was normal but dropped to 9.8V during startup. Voltage at the IPB fuse output measured only 10.2V with the key ON, while the distribution box input (B+) showed 12.4V—a 2.2V drop. Inspection of the front compartment distribution box revealed severely burnt and blackened contacts on the IPB power relay, with contact resistance of 0.8Ω. Replaced the front compartment distribution box assembly (part number: SA-XXX-XXXX) and checked the IPB module for internal shorts causing excessive current. Post-replacement voltage at the IPB measured 12.3V; fault resolved.
Original source ↗
BYD DTC AI Analysis

Degraded low-voltage AGM battery triggers P056216 during cold start

✓
2021 Song PLUS DM-i. Two years in, the dash threw "Check Brake System" on cold starts. Scanned P056216. Fault appeared whenever ambient temp dropped below 10°C and cleared once warm. Static battery voltage measured 12.1V (low). CCA down to 45% of rated, SOH 60%. Cranking crashed voltage to 8.5V—below IPB threshold. Root cause: owner only took short trips with Battery Intelligent Charging off, so the battery sulfated from chronic undercharge. Fix: Replaced with genuine 60Ah AGM (E6A-XXX-XXXX), turned on Battery Intelligent Charging via the scan tool, and advised the owner to fully charge every two weeks. Cold start voltage now holds above 11.2V. Fault hasn't returned.
Original source ↗
BYD DTC AI Analysis

Oxidized body ground point caused intermittent IPB undervoltage

✓
When driving on rough roads, the instrument cluster intermittently flashed the brake warning light. The scanner showed P056216 as an intermittent fault. IPB supply voltage was normal, but checking the ground circuit revealed a 0.3V drop between the IPB housing and battery negative terminal, with unstable resistance. Found the G302 ground point on the left front longitudinal member had a loose ground wire bolt, plus white oxide and paint residue on the contact surface. Repair: Removed the ground wire, sanded the contact surface to bare metal with 80-grit sandpaper, applied conductive paste (not grease), and torqued the bolt to 9N·m. Also inspected the IPB housing ground wire (black heavy-gauge cable) ring terminal for cracks. After repair, ground voltage drop measured under 0.05V. Road-tested 50 km with no fault recurrence.
Original source ↗
BYD DTC AI Analysis

Unstable DC-DC converter output caused low system voltage while driving

✓
Driving in EV mode with headlights and A/C on, the instrument cluster showed a brake system fault. DTCs P056216 and U01A987 (IPB communication fault) appeared simultaneously. Battery voltage dropped instantly from 13.8V to 9.5V when high-power loads came on, fluctuating constantly. At the DC-DC low-voltage output terminals, voltage was unstable, oscillating between 12V and 14V. The scan tool showed a history of 'low-side overcurrent protection' in the DC-DC data stream. Inspection found an internal loose connection in the positive harness from the DC-DC converter to the battery (runs through the front compartment fuse box). Fix: Replaced the harness from the DC-DC to the fuse box (including fuse) and flashed the DC-DC control software to V2.3.5 or above. Post-repair load testing confirmed voltage stable at 13.5V±0.2V. Fault resolved.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV 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.