AU
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.

The B1694-00 fault code on the Atto 8 indicates the airbag control unit has detected low operating voltage (below 9.0V–10.5V), potentially preventing proper airbag deployment or causing unintentional deployment. This medium severity issue triggers a safety warning light and degraded mode. Common causes include a weak battery, charging system faults, or corroded ground connections at the SRS ECU. Due to recorded cases, typical repair cost data is available. Visit an authorised dealer immediately for diagnosis and repair.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Battery aging, low charge, or charging system fault: Battery voltage is below 11V, or generator output voltage is unstable, causing a voltage drop during startup or high-current load operation.
  • 2Ground point loose or oxidized: Loose or corroded SRS ECU housing ground and G10/G36 connector ground points (G10-28, G10-35, G36-35) increase circuit resistance (>1Ω).
  • 3Instrument panel junction box power supply fault: Abnormal output voltage at terminal G2C-3, or burnt IG1 main relay contacts or coil fault, causing insufficient power supply in the ON position.
  • 4Poor wiring harness connector contact: Terminal back-out, oxidation, or water ingress at key connectors such as G10, G36, and G2C, or open or short circuit within the power wiring harness.
  • 5SRS ECU internal fault: A damaged ECU internal power management module causes a false low-voltage report (confirm only after ruling out external circuits).
What To Do
  • 1
    Basic check: Measure battery static voltage (should be ≥12.4V) and startup/charging voltage (should be 13.5-14.5V). Check battery terminals for tightness and oxidation. Charge or replace battery if necessary.
  • 2
    Fuse check: Check if the SRS-related fuses in the instrument panel power distribution box (such as F2/17) are blown or have poor contact. Measure the voltage drop across the fuse holder.
  • 3
    Ground point check: Disconnect the negative battery terminal. Check the tightening torque of the ground bolts for the SRS ECU housing and G10-28/G10-35 (or G36-35) (normally 8-10 N·m). Clean off any oxidation. Measure the resistance between the ground points and the vehicle body (should be <1 Ω).
  • 4
    Power distribution box and relay check: Measure the voltage at terminal G2C-3 with the ignition ON (should be 11-14V). Remove the IG1 main relay (K2-1) and test it. Apply power to pins 1-2: pins 3-5 should have continuity (<10Ω). Remove power: pins 3-5 should be open circuit (>10KΩ). If abnormal, replace the relay or power distribution box.
  • 5
    Wiring harness continuity test: Disconnect connectors G10/G36. Measure the voltage to ground of the harness-side power wires (e.g., G10-1, G36-36) (11-14V with ignition ON). Measure the resistance to ground of the ground wires (<1Ω). Measure the continuity resistance from the harness side to the power distribution box (<1Ω).
  • 6
    ECU replacement verification: If all above checks are normal, disconnect all loads and retain only the basic power supply. If the fault code persists, replace the airbag ECU (Note: Perform coding and system calibration after replacement).
Real-World Cases
BYD DTC AI Analysis

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

✓
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

✓
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

✓
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.
Original source ↗
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.