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B1795-00

DTC B1795-00 indicates the airbag control module (SRS ECU) detects an abnormal short to vehicle power (B+) in the driver-side seat belt pretensioner drive circuit (second-stage firing circuit) — Qin Plus

Safety System

DTC B1795-00 indicates the airbag control module (SRS ECU) detects an abnormal short to vehicle power (B+) in the driver-side seat belt pretensioner drive circuit (second-stage firing circuit).

In a dual-stage pretensioner system, the second stage further tightens the seat belt during a severe collision.

Normally, this circuit remains open or low.

When the ECU detects the pretensioner circuit voltage continuously exceeding the threshold (near the 12V battery voltage), it registers a short to power.

This fault causes the ECU to immediately disable the pretensioner circuit and illuminate the airbag warning light.

In extreme cases, the pretensioner may fail to deploy or deploy abnormally during a collision.

This severe fault compromises occupant safety.

The B1795-00 fault code on the Qin Plus indicates a high-severity short to battery power in the driver-side seat belt pretensioner second-stage firing circuit. This can disable the pretensioner and turn on the airbag warning light, reducing crash protection. Common causes include damaged wiring under the driver’s seat or B-pillar trim, and corroded or deformed pretensioner connector terminals. 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 — Qin Plus
  • 1Long-term chafing and wear of the wiring harness under the driver's seat or inside the B-pillar trim panel damages the insulation, shorting the pretensioner wiring harness to the constant power supply wire (B+).
  • 2Water ingress, oxidation, or deformed terminals at the seat belt pretensioner connector (under the seat or in the B-pillar), causing a short circuit between the ignition circuit terminal and the power supply terminal.
  • 3SRS ECU internal drive transistor breakdown or control circuit fault causes the output terminal to continuously output high-level voltage.
  • 4Pretensioner internal squib shorts to the power supply, or squib resistance drops abnormally (below 1.5Ω).
  • 5During accident repairs, seat cover installation, or vehicle modifications, screws or brackets pinch the wiring harness, or incorrect connections cause a short to power in the pretensioner circuit.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes (or the time specified in the repair manual) to fully discharge the SRS capacitor and ensure the system is in a safe state.
  • 2
    Fault confirmation: Connect the diagnostic tool to read fault codes, confirm B1795-00 is active, record freeze frame data, and check for accompanying SRS fault codes.
  • 3
    Visual inspection: Remove the driver-side B-pillar lower trim panel and seat. Inspect the pretensioner wiring harness (section from the floor harness to the B-pillar/seat connector) for wear, crushing, water stains, or modifications. Focus on the harness fixing points near the seat slide rails.
  • 4
    Open circuit test: Disconnect the driver pretensioner connector. Use a multimeter to measure the voltage from both harness-side terminals to body ground and to the power supply. Normal voltage is 0V. Measure the resistance to ground. Normal resistance is infinite.
  • 5
    Pretensioner unit inspection: Measure the resistance between the two terminals of the pretensioner unit. The standard value is typically 2.0-3.0 Ω (refer to the specific vehicle repair manual). If the resistance is too low or continuity exists between the terminals and the housing, replace the pretensioner assembly.
  • 6
    Harness insulation check: Use a megohmmeter or multimeter high-resistance range to measure the insulation resistance between the pretensioner drive circuit (SRS ECU to pretensioner) and the vehicle body power harness. Resistance must be greater than 1MΩ; otherwise, repair or replace the harness.
  • 7
    ECU Diagnosis: If the wiring harness and pretensioner are normal, check the SRS ECU connector terminals for corrosion or backed-out pins. If necessary, use an oscilloscope to monitor the ECU output waveform to check for an internal ECU short circuit. Replace the SRS ECU and perform coding configuration if necessary.
  • 8
    Repair verification: After repairing or replacing the faulty component, reconnect all connectors and the battery, clear the fault code, perform an SRS system self-check (ignition switch ON; indicator should turn off), and simulate a crash test (use a dedicated test resistor in place of the pretensioner) to confirm normal system operation.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV300 seat track wiring harness chafed and shorted

✓
Airbag warning light stayed on. Diagnostic scan retrieved DTC B1795-00 (Driver Second Stage Seatbelt Pretensioner Short to Power). Inspection found the wiring harness under the driver's seat had chafed against the fore-aft adjustment rails over time, damaging the insulation and causing the pretensioner power wire to short to constant B+. Repaired the damaged wiring, rerouted the harness away from moving components, and secured it with dedicated cable clips. Cleared the fault codes; system returned to normal.
Original source ↗
BYD DTC AI Analysis

After accident repairs on the Qin 80, misaligned connector terminals caused a short circuit.

✓
A Qin 80 had its driver seat belt assembly replaced at a non-authorised repairer after a collision. The airbag warning light came on the day after delivery. Techs retrieved DTC B1795-00. Inspection found the pretensioner connector terminals installed incorrectly, causing the second-stage ignition circuit terminal to short against the power terminal. Reinstalling the terminals correctly and confirming the lock tabs engaged cleared the fault.
BYD DTC AI Analysis

BYD Qin EV450 – Water ingress into floor wiring harness after wading

✓
After driving through water, water entered the driver's side carpet and the airbag warning light stayed on with DTC B1795-00 stored. Inspection revealed the floor harness connector seal under the driver's seat had failed. Water ingress caused electrolytic oxidation between the terminals, dropping the insulation resistance between the pretensioner drive circuit and power supply circuit to 0.5Ω. Thoroughly cleaned and dried the connector, applied conductive protectant, and replaced the seal to clear the fault.
BYD DTC AI Analysis

Qin Pro SRS ECU internal driver circuit fault

✓
No accident history. Airbag warning light suddenly illuminated while driving. DTC B1795-00. Checked pretensioner wiring harness insulation and connectors—good. Pretensioner resistance measured 2.3Ω (normal). Disconnected pretensioner; ECU-side output terminals still outputting constant 12V. SRS ECU internal drive transistor shorted. Replaced SRS control unit, performed VIN coding and system configuration. Fault resolved.
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.