AU
B1695-00

DTC B1695-00 indicates the airbag control unit (SRS ECU) detected its operating supply voltage exceeds the system safety threshold (typically >16V) — Qin Plus

Safety System

DTC B1695-00 indicates the airbag control unit (SRS ECU) detected its operating supply voltage exceeds the system safety threshold (typically >16V).

On BYD new energy vehicles, this fault means the 12V low-voltage system supply voltage rose abnormally, exceeding the tolerance range of the SRS ECU internal circuits.

The SRS system is highly sensitive to voltage.

Excessive voltage can cause reference voltage drift in the internal A/D converter, capacitor breakdown, or unintended airbag deployment.

As a safety mechanism, the ECU illuminates the airbag warning lamp, stores the fault code, and enters a fail-safe mode.

This mode disables the airbags and seat belt pretensioners, preventing abnormal voltage from causing unintended deployment or failure during a collision.

The B1695-00 fault code on the Qin Plus indicates the airbag control unit has detected excessive voltage (over 16V) in the 12V system, forcing the SRS system into fail-safe mode and disabling the airbags and seat belt pretensioners. Severity is medium. This is typically caused by a faulty DC-DC converter or a failing 12V battery. You should visit an authorised dealer for diagnosis and repair. Typical repair cost data is available based on 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1DC-DC converter (high-voltage to low-voltage) fault or regulator failure causes output voltage to exceed 16V and prevents stabilization within the normal 13.5-14.5V range.
  • 212V battery aging, sulfation, or internal short circuit reduces charge acceptance, causing the terminal voltage to spike to an abnormally high level at the start of charging.
  • 3An intermittent short circuit between the SRS ECU power supply circuit and the high-voltage circuit, or poor contact in the ground circuit (GND) causing reference voltage drift, results in the ECU detecting a falsely high voltage.
  • 4Alternator regulator fault (when engine is running on hybrid models), causing excessive charging system output voltage (>15.5V).
  • 5Unauthorized vehicle modification with a high-power inverter, in-vehicle power amplifier, or additional charging equipment causes sudden power system load changes; the delayed voltage regulator response generates instantaneous high-voltage spikes.
What To Do
  • 1
    Use VDS2000 or the BYD dedicated diagnostic tool to read the DTC freeze frame data. Record the exact voltage, vehicle speed, timestamp, and system load status when the fault occurred to determine whether it is a persistent or intermittent fault.
  • 2
    Measure the current 12V battery static voltage (should be 12.4-12.8V with the vehicle off). Enter Ready mode or start the engine and measure the dynamic charging voltage. Verify if the voltage continuously exceeds 15.5V or exhibits fluctuation spikes.
  • 3
    For EV models, check the DC-DC converter output voltage; for hybrid/ICE models, check the alternator output voltage and regulator operating status to determine if the voltage regulation component has failed.
  • 4
    Disconnect the battery negative terminal, wait 3 minutes, then remove the SRS ECU. Check the voltage drop and circuit resistance at the ECU B+ (constant power), IG (ignition power), and GND (ground) terminals. Verify the ground circuit resistance is < 1Ω and the power supply wiring shows no damage or burn marks.
  • 5
    Perform a 12V battery health check (internal resistance test, cold cranking amps (CCA) test, charge and discharge curve test). Replace the battery if the internal resistance is >10mΩ or the CCA value is below 60% of the rated value.
  • 6
    Replace the faulty component (DC-DC converter, alternator regulator, battery, or wiring harness) based on the test results. After repair, use the diagnostic tool to clear the fault code and perform 3 complete ignition cycles (OFF→ON→START→ON→OFF) for a self-test.
  • 7
    Use the diagnostic tool to perform an SRS system function test and read the circuit resistance of the airbags, side curtain airbags, and seat belt pretensioners (normal: 1.5-3.0Ω). Confirm no new fault codes before returning the vehicle.
Real-World Cases
BYD DTC AI Analysis

BYD S6 alternator regulator fault causing SRS high voltage

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Symptoms: The airbag warning light stayed on constantly. A diagnostic scanner retrieved DTC B1695-00. The vehicle started and drove normally, but the SRS system was in a warning state. Diagnosis: Connected the diagnostic scanner and confirmed fault code B1695-00 (Power Supply Voltage Too High). According to the BYD S6 workshop manual, this code belongs to the SRS (Supplemental Restraint System) and indicates power supply voltage too high. Measured the SRS ECU supply voltage — it reached 16.8V, exceeding the normal range (10-14V). Checked the alternator output and found excessive voltage (reaching 16.5V), confirming alternator regulator failure. Inspected the battery and found signs of electrolyte boiling. Resolution: Replaced the alternator regulator assembly and the overcharged 12V battery. Repaired the charging system to restore output voltage to the normal range (13.5-14.5V). Cleared the fault codes, and the issue was resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV300 DC-DC converter output voltage abnormal

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Symptoms: While driving, the instrument cluster suddenly displayed 'Please check SRS system', and the 12V battery sight glass turned black. Diagnosis: Using the diagnostic tool, retrieved DTC B1695-00; freeze frame data showed system voltage was 17.2V when the fault occurred. Measured the DC-DC output voltage, which stabilised at 16.5V in Ready mode—significantly exceeding the normal range (13.8-14.2V). Inspected the DC-DC low-voltage output wiring harness and found no damage, but noticed a burnt smell from the DC-DC converter cooling vent. Measured the DC-DC internal power transistor drive signal and identified abnormal PWM duty cycle. Confirmed an internal DC-DC voltage feedback circuit fault. Solution: Replaced the DC-DC converter assembly (part number: EA-2202000) and the damaged 12V battery. Recalibrated the low-voltage system, which eliminated the fault.
BYD DTC AI Analysis

BYD E1: Loose SRS ECU power connector causes intermittent high voltage warning

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Symptoms: The airbag warning light occasionally illuminates when driving on rough roads and goes out after stopping and restarting. Frequency: about 1–2 times per week. Diagnosis: DTC B1695-00 retrieved, status: historical/intermittent. Static voltage readings normal, but shaking the wiring harness produced a 16.5V transient spike at the SRS ECU power terminal. Inspection found the SRS ECU power connector (black 24-pin) below the left A-pillar had oxidized pins and a loose lock, causing increased contact resistance (measured 2.3Ω). Resolution: Cleaned the connector pins with electronic cleaner, applied conductive protective grease, and replaced the connector retaining clip for a secure connection. After clearing the DTC, monitored for one month with no recurrence.
BYD DTC AI Analysis

BYD Qin 80 battery sulfation causing excessive charging voltage

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After sitting for three days, the vehicle displayed an SRS fault on startup. The 12V battery was frequently flat, but voltage rose very quickly when charging. Retrieved active DTC B1695-00. Charging voltage measured 15.8V. Battery test showed severe internal plate sulphation: internal resistance 18mΩ (normal <6mΩ), CCA only 40% of rated value. Battery ageing caused poor charge acceptance; the DC-DC converter or alternator compensated for the flat battery by charging at high current continuously, causing terminal voltage to spike rapidly and trigger SRS overvoltage protection. Replaced the AGM stop-start battery (12V 60Ah), performed battery registration, and cleared fault codes. System returned to normal.
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.