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P229900

P229900 is a BYD-specific fault code for the IPB (Intelligent Integrated Braking System) — Atto 8

Braking System

P229900 is a BYD-specific fault code for the IPB (Intelligent Integrated Braking System).

It indicates a signal logic mismatch between the brake pedal stroke sensor (BPS) and the accelerator pedal stroke sensor (APS), specifically an abnormal zero-point calibration (failure to return to zero).

In the IPB system, these two sensor signals must meet interlock logic: when the vehicle is stationary without pedal application, both sensors must simultaneously read zero; during operation, they must meet "brake priority" or "one-pedal" logic.

This fault indicates the IPB-ECU detects a non-zero output from the BPS or APS under expected zero-position conditions, or a mismatch in their signal change rates.

This fault triggers a safety protection mechanism, potentially causing regenerative braking failure, false Automatic Emergency Braking (AEB) activation, or limited power output (limp mode), severely compromising driving safety.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i False P229900 and Regenerative Braking Failure

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Vehicle: 2021 Song Plus DM-i, 32,000 km. Dashboard showed "Braking System Fault". Fault code P229900. Live data: BPS voltage 0.2V (below normal 0.5V), APS 0%. Found negative zero-point drift of brake pedal sensor. Internal BPS circuit fault in IPB assembly. Replaced IPB assembly (with ECU) and performed zero-point calibration. Resolved. Note: After IPB replacement, run bleed and calibration procedures with a diagnostic tool, or brake pedal travel increases.
BYD DTC AI Analysis

APS zero point lost after battery disconnect, causing adaptation failure

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Owner reported multiple warning lights on the dash after jump-starting a flat battery. Scanned P229900. Data stream showed BPS normal at 0.5V, but the APS main signal read 8% with the pedal released. Battery disconnect had erased the APS zero-point calibration. Fix: Connected a scan tool, entered the IPB system, and ran "Sensor Zero-Point Learning". Released both pedals fully, then floored each one per the prompts. Cleared codes. Road-tested 20 km with no recurrence. Repair shops should perform this calibration proactively after replacing or disconnecting the battery.
BYD DTC AI Analysis

Intermittent fault caused by IPB software version defect

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2021 Song PLUS DM-i intermittently triggered DTC P229900. When the fault occurred, the vehicle automatically exited energy regeneration, but it disappeared after a restart. Data stream showed normal BPS and APS signals; determined an IPB-ECU software logic error. Technical bulletins indicate early software versions (V1.0x) have a pedal signal sampling filter algorithm defect. Solution: Upgraded IPB software to V2.15 or higher, reconfigured vehicle parameters (VIN write), and performed sensor calibration. No recurrence after one month of monitoring.
BYD DTC AI Analysis

Internal fault in accelerator pedal sensor caused dual-sensor mismatch

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Sudden power loss while driving; vehicle limited to 40 km/h. Dashboard showed "Power System Fault" and "Brake System Fault". DTCs: P229900 and U0146 (lost communication with IPB). Checked APS data stream: APP1 read 15%, APP2 read 0%. Dual-channel signals were out of sync (normally proportional). Disassembled the accelerator pedal assembly; internal sliding resistor was worn, causing signal drift. Replaced the accelerator pedal assembly; signals synchronized at 0%/0%. Performed IPB and ECU matching procedure; fault cleared.
BYD DTC AI Analysis

Poor wiring harness contact causing intermittent signal fault

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Vehicle intermittently threw P229900 on rough roads; normal on smooth surfaces. Pin 16 (BPS signal line) of the BPS connector (24-pin black plug) on the IPB assembly had a loose connection—voltage fluctuated between 0.2V and 1.2V when moving the harness. The terminal clip failed. Repaired the harness terminal, applied conductive adhesive, and wrapped with waterproof tape. Checked floor harness retaining clips to prevent chafing. Continuous speed bump testing after repair showed no recurrence.
Other Atto 8 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.