AU
B1792-00

This fault code indicates the driver-side second stage seat belt pretensioner ignition circuit resistance falls below the normal threshold set by the SRS control unit (ACU) (typically 2 — Seal U

Safety System

This fault code indicates the driver-side second stage seat belt pretensioner ignition circuit resistance falls below the normal threshold set by the SRS control unit (ACU) (typically 2.0-4.0Ω; actual detected value below 1.5Ω or close to 0Ω).

The second stage pretensioner is part of the dual-stage gas generator system, providing progressive restraint force during a severe collision.

Low resistance typically indicates an internal squib short circuit, a wiring harness short to ground, or internal connector bridging.

This fault causes the ACU to disable the pretensioner function.

In extreme cases, the pretensioner may fail to deploy during a collision, or false fault detection during driving may continuously illuminate the SRS warning light, compromising the overall occupant restraint system protection strategy.

The B1792-00 fault code on the Seal U indicates low resistance in the driver-side second stage seat belt pretensioner ignition circuit. Severity is medium because the SRS control unit may disable the pretensioner, reducing protection in a crash and keeping the SRS warning light on. Common causes include an internal pretensioner squib short or water/corrosion damage in the seat or B-pillar wiring connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Pretensioner squib internal short circuit: Long-term exposure to heat and humidity, manufacturing defects, or chemical corrosion dampens the pyrotechnic charge, reducing insulation resistance between the two terminals.
  • 2Wiring harness connector fault: Water ingress in connectors under the driver's seat or near the B-pillar, bent/backed-out pins, terminal bridging, or corrosion causing the signal wire to short to ground or power.
  • 3Mechanical damage: Repeated friction from the seat track adjustment mechanism, improper seat removal/installation, or foreign object compression damages the pretensioner wiring harness insulation, causing a short to ground.
  • 4Seat belt retractor assembly fault: Internal short circuit in the pretensioner body, or contact between the retractor metal parts and the ignition terminal creating a low-resistance path.
  • 5ACU detection circuit misjudgment: A fault in the airbag control unit internal sampling resistor or A/D conversion circuit causes the system to misread a normal resistance value (less common, but requires inspection).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS backup power supply and prevent accidental airbag deployment.
  • 2
    Initial diagnosis: Use BYD VDS or Launch X431 to read all DTCs and freeze frame data, confirm whether B1792-00 is a Current Code or a History Code, and check for other SRS-related fault codes.
  • 3
    Circuit isolation: Remove the driver-side B-pillar trim, locate the seat belt pretensioner connector (usually a yellow waterproof plug), and disconnect the connector to isolate the pretensioner from the wiring harness.
  • 4
    Resistance measurement: Use a digital multimeter (low current range, <1mA) to measure the resistance directly across the pretensioner unit terminals. The standard value is 2.0-4.0 Ω. If the reading is below 1.5 Ω or close to 0 Ω, the pretensioner unit is short-circuited. Replace the seat belt retractor assembly.
  • 5
    Wiring harness inspection: Measure the resistance between the harness-side connector terminal and ground (should be >10MΩ) and the resistance between terminals (should be open circuit). Check for a short to ground or a short between wires. Carefully inspect the wiring harness insulation for wear near the seat rail.
  • 6
    Connector inspection: Inspect connector pins for backing out, bending, or green corrosion. Clean with electrical contact cleaner and verify the locking tab is intact. If the connector shows signs of water ingress, identify the source (e.g., poor window sealing).
  • 7
    ACU verification: If the pretensioner and wiring harness are normal, check the ACU connector pins for oxidation and measure continuity between the ACU and the pretensioner. If necessary, use an oscilloscope to check the ACU output detection pulse waveform.
  • 8
    Repair verification: After replacing the faulty component, reconnect all connectors, restore battery power, and clear the fault codes. Perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times). Verify the fault code does not return and the SRS warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 pretensioner shorted after driving through water

✓
A 2017 BYD Qin EV300 came in with the SRS warning light on after driving through flood water. Retrieved DTC B1792-00. Found water in the wiring harness connector beneath the driver's seat; resistance between the pretensioner terminals measured 0.8Ω. Disassembly revealed the connector seal had deteriorated, allowing water ingress that caused a micro-short between the terminals. Repair: Replaced the seat belt retractor assembly (pretensioner had shorted and failed), fitted a new waterproof connector with insulation treatment, and cleared the drainage holes beneath the seat. Fault cleared.
BYD DTC AI Analysis

Seat modification damaged the wiring harness

✓
One week after installing racing seats in their 2018 BYD Qin EV450, the owner saw DTC B1792-00. The technician found the pretensioner harness unsecured during the modification. The seat rail bracket had pinched the harness repeatedly, wearing through the insulation and shorting the core wire to ground. Repair: Cut out the damaged section, soldered the joint and insulated it with heat-shrink tubing. Re-secured the harness along the standard routing path with adequate clearance from moving parts. Cleared the code; operation normal.
BYD DTC AI Analysis

Pretensioner internal resistance drift due to ageing

✓
2017 Qin 100, 120,000 km. Intermittent DTC B1792-00: present when cold, clearing when hot. Pretensioner resistance dropped to 1.2Ω in cold conditions, returning to 2.5Ω when warm. Diagnosis: Moisture ingress and aging of the internal igniter propellant caused abnormal temperature coefficient. Fix: Replaced OEM driver's side seat belt retractor assembly. Fault eliminated. Note: Verify soft faults with multiple measurements across different temperature environments.
BYD DTC AI Analysis

Connector pin backed out causing short circuit

✓
Following accident repairs, the vehicle set DTC B1792-00. Inspection found the B-pillar pretensioner connector had been misaligned during reinstallation, causing one terminal to back out and bend, contacting the adjacent terminal and creating a short circuit. Repaired the pin, reinstalled it using a dedicated terminal removal tool, applied conductive paste to ensure good contact, and relocked the connector. Fault cleared.
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.