AU
B17A600

DTC B17A600 indicates the Airbag Control Unit (ACU) detects a triggered front impact sensor circuit or an abnormal signal — Seal U

Safety System

DTC B17A600 indicates the Airbag Control Unit (ACU) detects a triggered front impact sensor circuit or an abnormal signal.

This event-type DTC typically indicates the SRS system recorded a front collision event (regardless of severity), or the Front Impact Sensor (FIS) and its wiring harness have an electrical fault (such as a short circuit, open circuit, or abnormal impedance).

On BYD Qin PRO models, the front impact sensors typically mount on both sides of the front longitudinal rails or radiator support frame to detect front-end acceleration changes.

The ACU sets this code when it detects a sensor signal exceeding the threshold (>2.5g for a specific duration) or abnormal sensor circuit resistance (normally approx. 2.0-3.0kΩ).

This fault may prevent airbag deployment or cause accidental deployment.

Repair the vehicle immediately.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1The vehicle sustained a front-end collision (whether a minor scrape or a severe accident), the SRS module recorded the collision event, and the Collision Data Reset (CDR) procedure was not performed.
  • 2Front crash sensor internal fault (piezoelectric element aging, internal circuit short or open), causing it to send an incorrect acceleration signal to the ACU.
  • 3Poor contact, oxidation due to water ingress, or pin corrosion at the front collision sensor wiring harness connector causes abnormal circuit resistance (>10kΩ or <500Ω).
  • 4Airbag Control Unit (ACU) internal algorithm error or memory fault causing a false collision signal (often occurs with other SRS fault codes such as B17A100).
  • 5Front-end modifications (such as installing aftermarket radar or modifying headlights) accidentally damage the sensor wiring harness, causing a damaged shielding layer or a signal wire short to ground.
What To Do
  • 1
    Connect the VDS2000/BYD dedicated diagnostic tool, read all DTCs and Freeze Frame data, record the acceleration value (Delta-V) and trigger time at the moment of impact, and verify if this is a genuine collision record.
  • 2
    Perform a full vehicle DTC scan and check for related codes such as B17A100 (ACU internal fault), B17B100 (front left sensor fault), or B17B200 (front right sensor fault) to locate the specific fault side.
  • 3
    After disconnecting the battery negative terminal for 3 minutes, visually inspect the front crash sensor (located on the inner panel of the front longitudinal beam) for physical damage, cracks, or loose mounting. Verify the wiring harness connector seal is intact and check for signs of water ingress (green corrosion).
  • 4
    Use a multimeter to measure the front crash sensor circuit resistance (disconnect the ACU connector and measure at the wiring harness side). Normal resistance is 2.0-3.5 kΩ. If the resistance is 0 Ω (short circuit) or infinite (open circuit), inspect the wiring harness in sections. If the resistance is normal, replace the sensor.
  • 5
    After confirming a genuine collision and repairing the body damage, execute the 'Crash Data Reset' function (path: SRS system → Special Functions → Crash Data Reset) and re-perform 'Coding & Calibration'.
  • 6
    After clearing the DTC, perform an SRS system self-check (approx. 6 seconds) and confirm DTC B17A600 does not return. Perform a simulated crash test (use the dedicated diagnostic tool to trigger the sensor test mode; do not strike the sensor with a hammer) to verify the ACU receives the front sensor signal normally and the fault light turns off.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: SRS warning light stays on after low-speed rear-end collision

✓
2019 Qin Pro DM, 32,000 km. Rear-ended the vehicle ahead at approximately 15 km/h in urban driving. Front bumper slightly deformed but airbags did not deploy. VDS reported DTC B17A600 (Front Collision) and B17B100 (Front Left Collision Sensor Fault). Disassembly revealed a slightly deformed front left collision sensor mounting bracket and damaged internal piezoelectric element. Replaced the front left collision sensor, cleared collision data, and performed system calibration. Fault resolved. Key point: Impact can damage sensors even when airbags do not deploy.
BYD DTC AI Analysis

SRS false front collision fault after water ingress

✓
2018 Qin PRO fuel variant. After driving through floodwater in heavy rain, the dashboard showed "Check SRS System." DTC B17A600. Found water in the front impact sensor connector. Resistance between pin 1 (signal wire) and pin 2 (ground) measured 200Ω (normal: 2.8kΩ). Cleaned the connector, applied conductive anti-corrosion grease, and dried the harness with a heat gun—resistance returned to normal. Cleared the codes and spray-tested for leaks. Fault did not recur.
BYD DTC AI Analysis

Crash data not reset after accident repair caused residual fault codes.

✓
2019 BYD Qin Pro DM. After an outside shop replaced the front bumper and left front rail, VDS showed B17A600 continuously with no clear. The shop replaced only the damaged sensor without performing a crash data reset. Used BYD VDS to access SRS special functions, executed 'Clear Crash Memory', and completed VIN coding and sensor configuration. Fault code cleared and SRS warning light went out.
BYD DTC AI Analysis

ACU software error causes intermittent false warnings

✓
2018 Qin PRO petrol. SRS warning light illuminated intermittently while driving. Diagnostic tool showed B17A600 (current fault). Checked front and rear impact sensors and wiring harness; all normal. Measured sensor output voltage waveform and found intermittent spike interference. Upgraded ACU software to latest version (from V2.1 to V2.4), optimizing collision threshold algorithm and filtering logic. Tracked 500km after upgrade; fault did not recur.
Other Seal U 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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.