UK
AU
B174C1B

This fault code indicates the Airbag Control Module (ACM) detects the squib circuit resistance of the left rear side airbag (typically integrated into the left rear seat backrest side or C-pillar trim panel) exceeds the calibrated upper limit — Atto 3

Safety System

This fault code indicates the Airbag Control Module (ACM) detects the squib circuit resistance of the left rear side airbag (typically integrated into the left rear seat backrest side or C-pillar trim panel) exceeds the calibrated upper limit.

Normal airbag squib resistance ranges from 1.5Ω to 3.0Ω.

The ACM logs a 'high resistance' fault when it detects the value continuously exceeding the threshold (typically above 4.5Ω).

This active safety system functional fault means the airbag may deploy abnormally, deploy late, or fail to deploy completely during a side-impact collision, disabling side protection for the left rear passenger.

An abnormal drop in squib circuit conductivity causes this fault.

Increased contact resistance, a partial open circuit, or an aging internal squib spiral coil can trigger this condition.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM seat rail wiring harness wear caused resistance drift

✓
A 2019 Qin Pro DM with 32,000 km had an intermittent SRS warning light on the instrument cluster. Retrieved DTC B174C1B (current). Inspection found that when adjusting the left rear seat, the harness beneath the seat chafed against the metal edge of the seat rail, causing one copper wire to break 90% of the way through without fully severing, creating a high-resistance condition (measured at 6.8Ω). Repair: Cut and re-soldered the damaged wire, insulated it with double-layer heat shrink tubing, and repositioned the harness retaining clips to prevent further chafing. Cleared the fault code and monitored for one week; no recurrence.
BYD DTC AI Analysis

Water-wading vehicle airbag connector oxidation fault

✓
2018 BYD Qin Pro (petrol). Water entered the cabin, reaching seat height. Afterwards, the vehicle logged DTC B174C1B. Removed the left rear seat and found water stains and green copper corrosion inside the airbag harness connector (located on the left side of the seat frame). Surface oxidation on the pins increased contact resistance to 5.2 Ω. Repair: cleaned the male and female terminals thoroughly with precision electronic cleaner, lightly sanded the pins with fine sandpaper until metallic luster was restored, applied special conductive grease, and reconnected. Inspected other airbag harnesses on the same side—no abnormalities found. Reassembled the components and the fault was eliminated.
BYD DTC AI Analysis

Open circuit inside left rear side airbag

✓
2019 Qin Pro DM collision repair. After replacing the left rear side airbag, DTC B174C1B set. Measured the new airbag resistance: infinite. Diagnosed an open in the internal igniter, possibly due to improper transport or storage. Installed a second airbag assembly; resistance 2.1 Ω, normal. However, the fault returned after installation. Further inspection found the airbag control module connector had been jarred loose in the accident, causing pin 14 (left rear side airbag circuit) to back out. Repaired the pin; fault resolved.
BYD DTC AI Analysis

False fault - ACM internal detection circuit malfunction

✓
A 2018 BYD Qin Pro had DTC B174C1B, but the left rear side airbag resistance measured 2.0Ω (normal) and the wiring harness showed good continuity with no damage. Tried replacing the airbag assembly; the fault remained. Checked the ACM diagnostic pulse waveform with an oscilloscope and found it abnormal. Diagnosed an internal constant current source circuit fault in the SRS control module. Replaced the SRS control module (requires VIN matching and coding configuration), after which the fault code cleared and the system returned to normal.
BYD DTC AI Analysis

Poor connector contact in low-temperature conditions

✓
A 2019 Qin Pro DM owner in a cold northern region reported the SRS warning light coming on during winter morning startups and going out after driving for some time. The vehicle stored historical fault code B174C1B. Inspection found no oxidation on the airbag connector under the left rear seat, but at low temperatures (-15°C), thermal expansion and contraction created a micro-gap between the plug and socket, increasing contact resistance to 4.2Ω (threshold). Repair: Adjusted the connector locking tab to ensure full engagement, applied conductive grease rated for low-temperature performance to the pin surfaces, and added wiring harness securing points to relieve stress. Follow-up low-temperature testing confirmed the fault did not return.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.