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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.

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Cases Logged
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.
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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.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.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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.