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B1694-00

The SRS (airbag system) control unit records DTC B1694-00 when it detects its operating supply voltage falls below the calibrated threshold (typically 9 — Atto 8

Safety System

The SRS (airbag system) control unit records DTC B1694-00 when it detects its operating supply voltage falls below the calibrated threshold (typically 9.0V-10.5V, depending on specific vehicle calibration).

This fault indicates a voltage drop in the airbag ECU constant power or IGN supply circuit, which may prevent the airbag system from deploying properly during a collision or cause unintentional deployment while driving.

This fault triggers a safety system degraded mode.

The ECU illuminates the airbag fault warning lamp and stores the fault code.

On some models, this condition also limits functions such as the seat belt pretensioners and airbag backup power supply.

3
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Qin EV450 airbag warning light stays on after starting (B1694-00)

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Symptoms: After starting the vehicle, the airbag warning light stayed on constantly. The diagnostic scanner retrieved code B1694-00 (Supply Voltage Low). Diagnostic Process: Measured battery voltage at 12.2V (low), but the charging system worked normally. Checked the G36 connector and found the G36-35 ground terminal loose. Measured resistance to ground at 3.2Ω (exceeded specification). Cleaned the ground point and tightened the connection, reducing resistance to 0.3Ω. Cleared the fault code and the system returned to normal. Resolution: Tightened the SRS system ground point. Advised the owner to check battery health (4 years old, replacement recommended).
Original source ↗
BYD DTC AI Analysis

BYD S6 intermittently logs B1694-00 fault

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Symptoms: Airbag light would intermittently come on while driving, then clear after stopping and restarting. Historical DTC B1694-00 stored. Diagnosis: Checked battery and alternator – both normal. Found slight burning on the IG1 main relay (K2-1) contacts in the instrument panel fuse box. Measured resistance between relay pins 3-5; it was unstable, sometimes exceeding 20Ω. Replaced the relay and road tested; voltage at terminal G2C-3 stayed stable and the fault did not recur. Fix: Replaced IG1 main relay; inspected fuse box base – no signs of burning.
Original source ↗
BYD DTC AI Analysis

E1 EV low voltage with multiple system faults

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Symptoms: E1 model instrument cluster displayed the airbag warning light and system fault light simultaneously. Scanned the SRS system, retrieved DTC B1694-00. Diagnosis: Inspection found an aftermarket dashcam fitted with non-standard power tapping causing voltage drop. Measured G10-1 terminal voltage dropped to 9.8V with headlights switched on. Restored factory wiring and separately checked the SRS power supply circuit. Found G2C-3 terminal pin backed out, causing poor contact. Solution: Repaired the backed-out terminal pin, eliminated the non-standard power tapping, and confirmed voltage stable above 12.5V under load.
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Other Atto 8 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.