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B178E-00

This DTC indicates the airbag control unit (SRS ECU) detects a short to vehicle power (12V/B+) in the front passenger airbag Stage 2 inflator circuit — Atto 3

Safety System

This DTC indicates the airbag control unit (SRS ECU) detects a short to vehicle power (12V/B+) in the front passenger airbag Stage 2 inflator circuit.

Dual-stage airbags feature two independent inflators for different crash severities: Stage 1 provides cushioning in minor collisions, and Stage 2 provides additional protection in severe collisions.

A short to power indicates an abnormal electrical connection between the inflator wiring and the battery positive terminal.

This fault causes the SRS system to enter fail-safe mode, illuminates the airbag warning light, and disables the front passenger airbag Stage 2 deployment function.

In extreme cases, it causes unintended airbag deployment or prevents normal deployment during a collision, creating a severe safety risk.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Clock spring internal short caused intermittent fault

✓
A 2018 BYD Qin EV450 intermittently illuminated the airbag warning light on the instrument cluster. DTC B178E-00 was retrieved. The fault appeared randomly, increasing in frequency when turning the steering wheel. The technician disconnected the airbag module and measured the harness from the clock spring to the SRS ECU, finding a short to power. Disassembling the clock spring revealed that at full steering lock, the second-stage igniter line in the internal flat cable was contacting the power supply line. After replacing the clock spring, the technician tested steering at full lock left and right; no recurrence.
BYD DTC AI Analysis

Dashboard modification pinched wiring harness, causing short circuit

✓
2017 BYD Qin 100. Owner reported constant airbag warning light, DTC B178E-00. Vehicle recently had a large centre console screen installed at an aftermarket shop. Technician found passenger-side dashboard bracket mounting screws were too long, piercing the SRS wiring harness sheath and causing a short between the second-stage igniter power and signal lines. Repaired harness damage (rewrapped with insulation), replaced damaged harness section, adjusted screw length. Cleared the fault. Advised owner to use professional repair shops for dashboard disassembly and reassembly.
BYD DTC AI Analysis

Connector corrosion and short circuit after water ingress

✓
A Qin EV300's airbag warning light illuminated after driving through deep flood water. Code B178E-00 stored and would not clear. Checked the passenger airbag connector (behind the glovebox) and found water staining and copper corrosion inside; degraded insulation between the terminals caused a short to power. Cleaned the connector with electronic contact cleaner, dried it with compressed air, and applied conductive anti-corrosion grease. Insulation resistance returned to normal. Cleared the code and the system returned to normal. Recommend checking the vehicle's water ingress sealing.
BYD DTC AI Analysis

SRS ECU internal driver chip failure

✓
2017 BYD Qin 80, no accident history. SRS warning light suddenly illuminated. Scan tool retrieved DTC B178E-00. Measured passenger airbag second stage igniter circuit to ECU — no external short. Disconnected ECU connector and measured harness side — normal. Reconnected ECU and fault returned. Disassembled SRS ECU and found internal igniter driver ASIC chip burnt out, causing internal short to power at second stage igniter output. Replaced SRS ECU, programmed and matched — fault resolved. Old ECU failed due to internal component ageing.
BYD DTC AI Analysis

Internal squib short circuit in airbag module

✓
During routine maintenance at a 4S dealership, a technician noticed the airbag warning light on in a Qin EV450 and retrieved DTC B178E-00. Measuring at the passenger airbag module connector revealed the second stage squib was shorted between both pins and to power. They disconnected the module and checked the squib pins on the module side: 0.5Ω with continuity to the housing, confirming an internal short in the second stage squib to the housing (ground/power reference). They replaced the passenger airbag assembly (including the module). The new module measured 2.1Ω and showed no continuity to the housing. Installation cleared the fault.
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.