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P229900

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

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
5
Causes
Likely Causes — Qin Plus
  • 1Brake Pedal Position Sensor (BPS) zero-point drift or internal potentiometer wear causes a non-zero voltage output signal with the pedal released (normal reference value is approximately 0.5V).
  • 2Accelerator pedal position sensor (APS) main and secondary signal channels (APP1/APP2) synchronization deviation, or loss of zero-point calibration data; commonly occurs after disconnecting the battery without performing the reset procedure.
  • 3Internal ECU sampling circuit fault in the IPB electro-hydraulic module causing BPS signal A/D conversion errors, or abnormal software logic evaluation.
  • 4Poor contact, water ingress, or oxidation at the sensor wiring harness connector, or a damaged shielding layer, causing electromagnetic interference in the signal wires (typically analog voltage for BPS and dual-channel PWM for APS).
  • 5Mechanical binding in the pedal mechanism, return spring fatigue, or loose mounting bolts, preventing the pedal from fully returning to its mechanical zero position.
What To Do
  • 1
    Connect the VDS2000/VDS3000 diagnostic tool, enter the IPB system, and read the freeze frame data. Record the BPS voltage (normal range 0.4-0.6V) and APS percentage (should be <5%) at the time of the fault to confirm which sensor deviated from the zero position.
  • 2
    Perform the 'IPB Sensor Zero Point Calibration' function (path: IPB System → Special Functions → Sensor Zero Point Learning). Follow the prompts to complete the brake pedal and accelerator pedal zero point self-learning, and observe whether the data stream returns to normal.
  • 3
    If calibration fails, disconnect the 12V battery negative terminal for 5 minutes, restore power, and repeat the calibration procedure. Check the IPB system software version. If an update is available (e.g., early Song PLUS DM-i versions had a P229900 false positive bug), upgrade to the latest version.
  • 4
    Inspect the connector pins of the BPS sensor (located on the brake master cylinder/IPB assembly) and the APS sensor (located on the accelerator pedal assembly) for back-out or corrosion. Measure the BPS signal wire (usually yellow/green) voltage to ground to verify it is within 0.5V±0.1V.
  • 5
    If wiring is normal but the signal remains abnormal, replace the corresponding sensor: for BPS, replace the IPB assembly (integrated design) or the pedal position sensor (some models allow separate replacement); for APS, replace the accelerator pedal assembly. After replacement, perform a zero-point calibration and verify with a road test.
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 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.