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B2A4E13

DTC B2A4E13 indicates an open control circuit fault in the left front (driver side) seat belt pretensioner — Seal 6 EV

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.

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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Seat belt pretensioner connector plug under the left front seat is loose, not fully locked, or has oxidized/corroded terminals, causing excessive contact resistance or an open circuit.
  • 2Repeated bending during fore-and-aft seat movement breaks internal wires in the wiring harness transition area between the vehicle floor and the seat (especially near the seat slide rail).
  • 3Vehicle wading or damp environments cause water ingress and oxidation at the pretensioner connector, or a damaged wiring harness sleeve causes terminal corrosion.
  • 4Open circuit in the seat belt pretensioner internal resistance wire (normal resistance: 2-5 Ω; displays infinity when faulty).
  • 5Airbag Control Unit (ACU) internal monitoring circuit fault, or connector pins backed out or deformed.
What To Do
  • 1
    Safety preparation: Set the vehicle to 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 under the seat (pretensioner connector) is fully locked. Inspect for 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 shows infinity or is greater than 10 Ω, the pretensioner body or wiring has an open circuit.
  • 4
    Wiring harness inspection: Focus on the wiring harness transition area from the vehicle floor to the seat (especially the bend at the seat slide rail). Peel back the protective sleeve and inspect the wires for wear or breakage. Check for missing wiring harness retaining clips causing movement.
  • 5
    Continuity test: Disconnect the ACU connector and measure wiring continuity from the pretensioner to the corresponding ACU pins. Verify there are no open circuits or poor connections.
  • 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 during removal.)
  • 7
    System reset: Reconnect all connectors and verify they lock. 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 Seal 6 EV 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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.