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B2A4E13

DTC B2A4E13 indicates an open control circuit fault in the left front (driver side) seat belt pretensioner — Qin Plus

Thermal Management System

DTC B2A4E13 indicates an open control circuit fault in the left front (driver side) seat belt pretensioner.

It belongs to the body safety system (SRS), not the thermal management system.

DTC structure breakdown: 'B' represents the Body system, '2A4E' designates the left front seat belt pretensioner control circuit, and '13' indicates an open circuit.

The Airbag Control Unit (ACU) triggers this fault upon detecting abnormal resistance (open circuit or excessive resistance) in the pretensioner circuit, which prevents the formation of an effective monitoring circuit.

This fault continuously illuminates the instrument cluster SRS warning light and forces the airbag system into a degraded mode.

In extreme cases, it prevents the pretensioner from deploying during a collision, posing a severe safety risk.

Note: Unofficial sources sometimes incorrectly label this code as a high-voltage line pressure sensor fault; it strictly indicates a seat belt pretensioner circuit fault.

The B2A4E13 fault code on the Qin Plus indicates an open circuit in the left front driver seat belt pretensioner control circuit. This is a high-severity SRS safety fault because the pretensioner may not work in a crash and the airbag system may enter degraded mode. Common causes include a loose under-seat connector or damaged wiring near the seat track. Visit an authorised dealer for inspection and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Loose or incompletely locked seat belt pretensioner connector plug under the left front seat, or oxidized or corroded terminals, causing excessive contact resistance or an open circuit.
  • 2During fore-and-aft seat movement, repeated bending in the wiring harness transition area between the vehicle floor and the seat, especially near the seat track, breaks the internal wires.
  • 3Vehicle wading or damp environments caused water ingress and oxidation at the pretensioner connector, or a damaged wiring harness sheath caused terminal corrosion.
  • 4Open circuit in the seat belt pretensioner unit internal resistance wire (normal resistance: 2-5Ω; reads infinite when faulty)
  • 5Airbag Control Unit (ACU) internal monitoring circuit fault, or connector pins backed out or deformed
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the airbag system and prevent accidental deployment.
  • 2
    Visual inspection: Remove the left front seat (leave the wiring harness connected). Verify the yellow plug (pretensioner connector) under the seat is fully locked. Inspect for signs of water ingress, oxidation, or burn marks.
  • 3
    Resistance measurement: Use a multimeter to measure the resistance between the pretensioner connector terminals. Standard value: 2-5 Ω. If the reading is infinite or greater than 10 Ω, this indicates an open circuit in the pretensioner body or wiring.
  • 4
    Wiring harness inspection: Inspect the harness transition area from the body floor to the seat, especially the bend at the seat slide rail. Peel back the protective sleeve to inspect the wires for wear or breaks. Check for missing harness retaining clips causing movement.
  • 5
    Continuity test: Disconnect the ACU connector. Measure wiring continuity between the pretensioner and the corresponding ACU pin to verify there is no open circuit or poor connection.
  • 6
    Component replacement: If the wiring harness is damaged, repair or replace the seat wiring harness assembly. If the pretensioner body resistance is abnormal, replace the pretensioner (Note: The pretensioner is an explosive device; never use brute force to remove it).
  • 7
    System reset: Reconnect all connectors and confirm they are locked. Connect the battery. Use the BYD VDS or ED-400 diagnostic tool to clear the fault codes. Perform an SRS system self-check. Confirm the warning light turns off and no current fault codes remain.
Real-World Cases
BYD DTC AI Analysis

Worn seat rail wiring harness caused intermittent open circuit on Song Pro DM-i

✓
2019 Song Pro DM-i. Instrument cluster intermittently displayed 'SRS System Fault'. Retrieved DTC B2A4E13. Found the wiring harness beneath the left front seat had chafed at the seat rail from repeated fore-aft movement, wearing through the insulation. The yellow/black wire inside was nearly severed, causing intermittent poor contact. Replaced the seat wiring harness assembly, rerouted and secured it, added anti-chafe sleeving and retaining clips to prevent strain during seat movement. Cleared the DTC and monitored for one week with no recurrence.
Original source ↗
BYD DTC AI Analysis

New Qin L DM-i pretensioner plug improperly installed.

✓
After delivery of a new 2024 Qin L DM-i, the instrument cluster intermittently displayed an airbag fault. DTC B2A4E13 cleared but returned repeatedly. Removing the left front seat revealed the seatbelt pretensioner connector was not fully locked (production line assembly defect); the missing wiring harness retaining clip allowed the connector to vibrate while driving, causing poor contact. Solution: Reconnected the connector and confirmed positive locking, installed the missing wiring harness retaining clip, and secured the harness routing with cable ties.
Original source ↗
BYD DTC AI Analysis

Sudden airbag warning on Song DM after driving on rough roads

✓
A 2019 BYD Song DM owner reported the dashboard suddenly displayed an airbag fault after driving over a bumpy road. The dealership's initial inspection found no issues. The owner used a diagnostic scanner to retrieve code B2A4E13, then reproduced the fault by wiggling the seat wiring harness. Inspection revealed multiple terminals inside the connector between the floor pan and seat (the large plug beneath the seat) had loose connections, with the yellow/black pretensioner control wire terminal almost completely backed out. Fix: Removed the terminals using a special terminal removal tool, re-crimped them, applied conductive anti-corrosion grease, and secured all seat-related connectors.
Original source ↗
BYD DTC AI Analysis

Multiple models: Oxidized pretensioner connector after water wading

✓
Applies to Song, Qin, Han and related model ranges. DTC B2A4E13 present with related codes including B1890. Vehicle has water wading history. Diagnosis: Pretensioner connector showed obvious water ingress and oxidation; resistance readings unstable. Repair: Clean connector terminals and apply conductive paste. Replace connector if oxidation is severe. Check harness boot seal and replace seat harness assembly if necessary. If water entered the pretensioner body, replace pretensioner assembly and check ACU.
Original source ↗
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.