AU
B2A4E13

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

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
5
Causes
Likely Causes — Seal U
  • 1Seat belt pretensioner connector under the left front seat loose or not fully locked, or terminals oxidized or corroded, causing excessive contact resistance or an open circuit.
  • 2Repeated bending during fore-and-aft seat movement breaks internal wires in the harness transition area between the vehicle floor and the seat (especially near the seat track).
  • 3Vehicle wading or damp environments cause water ingress and oxidation in the pretensioner connector, or a damaged wiring harness sleeve causes terminal corrosion.
  • 4Open circuit in the internal resistance wire of the seat belt pretensioner assembly (normal resistance: 2-5 Ω; displays infinity when faulty)
  • 5Airbag Control Unit (ACU) internal monitoring circuit fault, or backed-out or deformed connector pins
What To Do
  • 1
    Safety preparation: Turn 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 (keep the wiring harness connected). Verify the yellow plug (pretensioner connector) under the seat 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: 2-5Ω. A reading of infinity or greater than 10Ω indicates an open circuit in the pretensioner body or wiring.
  • 4
    Wiring harness inspection: Closely inspect the wiring harness transition area from the vehicle floor to the seat (especially the bend at the seat slide rail). Strip back the protective sleeve and inspect the wires for wear or breaks. Check for missing wiring harness retaining clips allowing harness movement.
  • 5
    Continuity test: Disconnect the ACU connector. Measure wiring continuity between the pretensioner and the corresponding ACU pins. 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 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. Verify the warning light turns off and no current fault codes exist.
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 U Fault Codes
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.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.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.