UK
AU
B164B-00

DTC B164B-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path (typically <1Ω) from the front passenger seat belt pretensioner ignition circuit to body ground — Atto 3

Safety System

DTC B164B-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path (typically <1Ω) from the front passenger seat belt pretensioner ignition circuit to body ground.

The pretensioner is a pyrotechnic safety device containing an igniter and a gas generator, with a normal resistance of approximately 2.0-3.0Ω.

A short to ground indicates damaged insulation on at least one of the two ignition circuit wires contacting vehicle body metal, or an internal short circuit within the pretensioner igniter.

The system classifies this fault as severe because: 1) the short circuit can cause unintentional pretensioner deployment, injuring the occupant; 2) it can prevent pretensioner deployment during a collision, causing a loss of restraint protection; 3) the SRS system enters fail-safe mode, which can disable the front airbags.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Seat adjustment chafed the wiring harness, causing a short circuit.

✓
A 2017 BYD Qin EV300, 80,000 km. The owner reported the airbag warning light stayed on constantly. Scanned DTC B164B-00. Found that with the passenger seat adjusted fully rearward, the pretensioner wiring harness beneath the seat was rubbing against the metal edge of the seat rail. Long-term friction had worn through the yellow corrugated tubing, allowing the copper wires to short directly to the seat frame. Repositioned the harness, wrapped the damaged section with three layers of heat-resistant insulating tape, secured it with an additional plastic protective sleeve, and rerouted the wiring to avoid interference with moving parts. Fault resolved.
BYD DTC AI Analysis

Connectors on the water-damaged vehicle oxidised and short-circuited

✓
A 2018 Qin EV450. Poor front windscreen sealing allowed rainwater to leak into the passenger side A‑pillar interior trim and travel along the wiring harness into the pretensioner connector. Disassembly revealed severely oxidised (green) terminals inside the connector, causing a short circuit between the terminals and the connector metal housing. The warning light illuminated in wet weather and occasionally cleared when dry. Replaced the pretensioner wiring harness connector by cutting off the old plug, soldering on the new plug, and waterproofing the joint. Applied waterproof silicone grease to the pretensioner socket. Repaired the windscreen seal. The fault has not returned.
BYD DTC AI Analysis

Internal damage to pretensioner after accident repair

✓
Replaced the front passenger seatbelt assembly (including pretensioner) on a 2017 BYD Qin 100 following front collision repairs, but the airbag warning light stayed on. Could not clear DTC B164B-00. Measured the new pretensioner resistance at 0.8Ω (abnormally low), indicating a parts quality defect or internal igniter short caused by impact during transport. Fitted a brand new genuine pretensioner, and resistance returned to normal at 2.3Ω. Cleared the DTC, and the system returned to normal. Caution: Pretensioners are explosive devices; avoid dropping during transport and storage.
BYD DTC AI Analysis

Aftermarket seat heater installation pierced the wiring harness.

✓
The owner of a 2017 Qin 80 had a passenger seat heating pad installed at an auto parts market. The installer used self-tapping screws that were too long when securing the heating pad. The screws penetrated the seat foam and punctured the pretensioner wiring harness, causing a short to ground. The fault appeared the next day when the airbag light came on. Inspection found two unauthorised screws beneath the seat. One had pierced straight through the yellow pretensioner harness. Repair: removed the screws, replaced the entire pretensioner harness (replaced the whole harness for safety), rerouted the wiring away from the aftermarket parts, and cleared the fault codes.
BYD DTC AI Analysis

SRS ECU internal drive circuit fault

✓
A 2017 Qin EV300 repeatedly logged DTC B164B-00, with the fault returning within days after each clear. Replaced the pretensioner and wiring harness without success. In-depth inspection revealed the passenger-side pretensioner driver chip inside the SRS ECU had shorted to ground, causing the ECU to continuously detect a false short-to-ground condition. Such faults typically result from previous voltage instability, such as reverse polarity or voltage surges during jump-starting. Replaced the airbag control unit and used a dedicated diagnostic scanner to write the VIN and configure the system. This completely resolved 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.