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) — Atto 3

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 Atto 3 indicates the airbag control unit has detected excessive voltage (over 16V) in the 12V system, triggering a fail-safe mode that disables airbags and seatbelt pretensioners. Severity is medium. Common causes include a faulty DC-DC converter or voltage regulator, or a degraded 12V battery causing voltage spikes. The recommended fix is visiting an authorised dealer. Typical repair cost data is available based on 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1DC-DC converter (high-to-low voltage) fault or regulator failure causes output voltage to exceed 16V and fail to stabilize within the normal 13.5-14.5V range.
  • 212V battery aging, sulfation, or internal short circuit reduces charge acceptance, causing terminal voltage to spike to an abnormally high level during initial charging.
  • 3Intermittent short circuit between the SRS ECU power supply circuit and the high-voltage circuit, or poor contact in the ground circuit (GND), causes reference voltage drift, resulting in the ECU detecting a falsely high voltage.
  • 4Alternator regulator fault (with engine running on hybrid models), causing excessive charging system output voltage (>15.5V).
  • 5Unauthorized vehicle modification with a high-power inverter, audio amplifier, or additional charging equipment causes sudden power system load changes, resulting in a delayed voltage regulator response that generates instantaneous high-voltage spikes.
What To Do
  • 1
    Use the VDS2000 or BYD dedicated diagnostic tool to read the DTC freeze frame data. Record the exact voltage value, vehicle speed, timestamp, and system load status when the fault occurred to determine whether the fault is persistent or intermittent.
  • 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. Check if the voltage continuously exceeds 15.5V or shows fluctuation spikes.
  • 3
    For new energy vehicles, check the DC-DC converter output voltage. For hybrid/ICE vehicles, check the alternator output voltage and regulator operating status, and verify if the voltage regulation component has failed.
  • 4
    Disconnect the battery negative terminal, wait 3 minutes, and 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 burning.
  • 5
    Perform a 12V battery health check (internal resistance test, CCA cold cranking current test, charge/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 inspection results. After repair, use the diagnostic tool to clear the fault code and perform 3 complete ignition cycles (OFF→ON→START→ON→OFF) to run a self-test.
  • 7
    Use the diagnostic tool to perform the SRS system function test. Read the circuit resistance of the airbags, side curtain airbags, and seat belt pretensioners (normal: 1.5-3.0 Ω). Confirm no new fault codes exist 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 Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.