AU
P056200

The BYD IPB (Intelligent Power Brake) system logs DTC P056200 for abnormal supply voltage — Atto 8

Braking System

The BYD IPB (Intelligent Power Brake) system logs DTC P056200 for abnormal supply voltage.

This code is a manufacturer-specific extension of P0562.

The fault indicates the IPB control module detects the 12V system voltage remaining below the normal operating threshold (typically 9.5V-10V, depending on the software version).

Because the IPB system uses electro-hydraulic servo braking technology, its motor pump, solenoid valves, and ECU require highly stable voltage.

Insufficient voltage causes key safety functions, including the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), and Autonomous Emergency Braking (AEB), to fail or degrade.

In DM-i hybrid models, this fault typically relates to an abnormal DC-DC converter (which supplies the 12V system from the high-voltage battery), rather than a traditional alternator failure.

This is a safety-critical fault.

When triggered, the IPB enters degraded mode and illuminates multiple system warning lights on the instrument cluster.

The P056200 fault code on the Atto 8 indicates abnormal low 12V supply voltage to the IPB braking system. This is a medium-severity fault because ABS, ESC, AEB, and brake assist functions may be reduced. Common causes include a weak or discharged 12V battery, or a faulty DC-DC converter not charging correctly. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 112V low-voltage battery is aged, discharged, or has increased internal resistance, and cannot maintain stable IPB voltage under high-load conditions (especially during automatic emergency braking or frequent braking).
  • 2DC-DC converter fault or low output voltage preventing the high-voltage system from properly charging the 12V battery (specific to new energy vehicles; output must remain at 13.8V-14.5V).
  • 3Poor connection in the IPB module power supply circuit, oxidized fuse holder, or burnt relay contacts, causing excessive voltage drop under high-current operating conditions.
  • 4IPB module ground point (usually G601 or main body ground point) is loose, oxidized, or making poor contact, causing increased circuit resistance.
  • 5Fault in the IPB control module internal power management circuit or voltage sampling circuit, causing false faults or failure to adapt to low-voltage operating conditions.
What To Do
  • 1
    Use the VDS2000/3000 diagnostic tool to read the complete fault codes and freeze frame data. Specifically record the system voltage value, vehicle speed, and brake pedal status when the fault occurred. Confirm whether the fault is persistent or intermittent.
  • 2
    Measure the 12V battery static voltage (should be ≥12.4V) and dynamic load voltage (≥11.5V with headlights and air conditioning on). Use a battery tester to measure the CCA value and internal resistance to determine the battery state of health. Replace the battery if SOH < 70%.
  • 3
    With the vehicle powered on and in READY mode, measure the voltage across the battery positive and negative terminals and check the DC-DC converter output (normal range: 13.5V-14.8V; if below 13V, check the DC-DC converter and related high-voltage connections).
  • 4
    Disconnect the IPB module connector (usually located near the firewall in the engine bay). Check the pins for backing out, corrosion, or water ingress. Measure the B+ terminal to ground voltage (must match battery voltage, voltage difference <0.3V) and the ground resistance (must be <1Ω).
  • 5
    Inspect the IPB main power supply fuse (usually a 40A-60A high-current fuse) and the engine compartment power distribution box base for signs of burning or melting. If necessary, sand the fuse terminals and apply conductive grease.
  • 6
    Check the IPB module body ground point, sand off the oxidation layer, and tighten to the specified torque (typically 8-10 N·m). Add an auxiliary ground wire if necessary.
  • 7
    If circuit measurements are normal, power-cycle the IPB module (disconnect the 12V battery negative terminal for at least 5 minutes). Clear the fault code and perform a road test. If the fault recurs, replace the IPB integrated electro-hydraulic brake assembly.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i: IPB Low Voltage Warning Caused by Battery Aging

✓
A 2021 Song Plus DM-i at 32,000 km showed an intermittent ABS/ESC warning light during cold starts. Scan tool read P056200. Measured static battery voltage at 12.1V, dropping to 10.8V under load test; internal resistance was 8.5mΩ (spec <5mΩ). Replaced the AGM start-stop battery. IPB supply voltage stable at 13.8V; fault resolved. The DM-i's frequent start-stop operation caused deep cycle aging of the 12V battery.
BYD DTC AI Analysis

Insufficient DC-DC converter output caused brake system fault

✓
The brake system warning light suddenly illuminated while driving, disabling automatic emergency braking. Read DTC P056200; measured DC-DC output at only 12.3V (normal approximately 14V). Inspected the high-voltage distribution box DC-DC high-voltage input connector and found the interlock pin backed out, limiting DC-DC output. Repaired the connector; DC-DC output returned to normal. Cleared the fault code and the issue did not reoccur.
BYD DTC AI Analysis

Oxidized ground point on IPB module caused intermittent low voltage

✓
When driving over speed humps or rough roads, the brake system warning light occasionally illuminated. Inspection found obvious oxidation and looseness at IPB module ground point G601 on the left front side member. Fastening torque measured only 3 N·m (standard 9 N·m). Ground circuit resistance jumped from 0.5 Ω to 12 Ω when wiggling the wiring harness. After cleaning the ground surface and retightening, the fault did not recur during a continuous 50 km road test.
BYD DTC AI Analysis

Burnt engine bay fuse holder causing voltage drop

✓
After extended use, the vehicle set code P056200. Battery voltage tested normal, but B+ voltage at the IPB connector dropped from 13.8V to 9.2V under braking. The IPB power supply fuse (60A) holder in the engine compartment fuse box had burnt and carbonized, increasing contact resistance. Replaced the fuse box assembly and main harness connector. Fault cleared.
BYD DTC AI Analysis

Low temperatures degraded battery performance, triggering fault

✓
At -15°C in a Northern winter, the vehicle logged P056200 immediately on startup after overnight parking. Testing revealed the battery cold cranking amps (CCA) had degraded to 60% of the rated value. High current demand during IPB self-check caused voltage to momentarily drop below 9V. Replaced the battery with an AGM unit offering better low-temperature performance and advised the customer to connect a battery maintainer during extended storage. Issue resolved.
Other Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.