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P056216

P056216 is a BYD IPB (Intelligent Power Brake) extended fault code — Qin Plus

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.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Low-voltage battery aging or depletion: The 12V battery in BYD hybrid/pure electric models (typically AGM or EFB) reaches the end of its service life or suffers 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 terminal or loose connection at the power supply connector from the front compartment 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 causes unstable output voltage at the IPB power supply terminal.
  • 4Poor ground point: The IPB module ground point (typically G301, G302, or the left front longitudinal beam ground point) is loose, oxidized, or has paint residue, increasing circuit resistance.
  • 5DC-DC converter fault (new energy vehicles): The on-board DC-DC converter produces abnormal output when converting high voltage to 12V low voltage, or the low-voltage charging strategy fails, causing 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. Check the freeze frame data to record the exact voltage value when the fault occurred (e.g., Battery Voltage: 8.2V). Confirm the vehicle speed, mileage, and other conditions at the time of the fault to distinguish between a static power loss and a dynamic power supply fault.
  • 2
    Low-voltage battery status check: Measure battery static voltage (must be ≥12.4V), perform an internal resistance test (CCA value must be ≥70% of rated value), and check battery terminals for oxidation or looseness. If voltage is below 12V or internal resistance is excessive, replace with an OEM AGM battery first.
  • 3
    IPB power supply circuit static check: Check if the IPB-related fuses in the front compartment power distribution box (usually F4/9, F4/10, or 30A/40A fuses marked "IPB" or "ESC") are blown or oxidized. Check the IPB wiring harness connectors (Connector A is a large 26-pin connector; Connector B is a small 12-pin connector) for backed-out terminals, 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 must be ≥11.5V. Measure the voltage drop between the IPB ground point (usually connected to the left front longitudinal beam) and the battery negative terminal. Voltage drop must be ＜0.1V. An excessive voltage difference indicates high resistance in the circuit.
  • 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 ground points: Remove IPB ground points (G301/G302). Sand the contact surfaces to bare metal. Apply conductive grease and tighten to the standard torque (usually 8-10N·m). Inspect the body ground stud for stripped threads.
  • 7
    DC-DC function check (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, reflash 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 the diagnostic tool to execute the "Electro-hydraulic Brake System Bleeding" process). Road test the vehicle to confirm normal brake pedal effort and verify no warning lights illuminate. 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 Qin Plus 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.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.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.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.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 Qin Plus →Qin Plus 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.