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 8

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 8 indicates the airbag control unit has detected excessive voltage (over 16V) in the 12V system, triggering a fail-safe mode that disables the airbags and seat belt pretensioners. Severity is medium. Common causes include a faulty DC-DC converter or a degraded 12V battery. 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 — Atto 8
  • 1DC-DC converter (high voltage to low voltage) fault or regulator failure causing 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 the 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 ground circuit (GND) contact causing reference voltage drift, resulting in the ECU detecting a falsely high voltage.
  • 4Alternator regulator fault (during engine operation 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, delaying the voltage regulator response and generating instantaneous high-voltage spikes.
What To Do
  • 1
    Use the VDS2000 or a dedicated BYD diagnostic tool to read the DTC freeze frame data. Record the exact voltage, vehicle speed, timestamp, and system load status when the fault occurred. Determine whether the fault is persistent or intermittent.
  • 2
    Measure the current 12V battery static voltage (12.4-12.8V with ignition off). Enter Ready mode or start the engine and measure the dynamic charging voltage. Verify 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 condition to verify 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/discharge curve test). Replace the battery if the internal resistance is >10mΩ or the CCA value is below 60% of the rated value.
  • 6
    Based on the inspection results, replace the faulty component (DC-DC converter, alternator regulator, battery, or wiring harness). 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. Read the circuit resistance of the airbag, side curtain airbag, and seat belt pretensioner (normal: 1.5-3.0Ω). Confirm no new fault codes are present 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 8 Fault Codes
B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.