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B161C-00

DTC B161C-00 indicates the Supplemental Restraint System (SRS) control unit detected the front passenger airbag (PAB) ignition circuit resistance exceeds the normal upper limit — Atto 8

Safety System

DTC B161C-00 indicates the Supplemental Restraint System (SRS) control unit detected the front passenger airbag (PAB) ignition circuit resistance exceeds the normal upper limit.

In BYD SRS systems, the control unit continuously monitors each airbag squib resistance via a low-current detection circuit.

The normal range is typically 2.0-3.0Ω.

If the resistance exceeds approximately 6.0Ω (high-resistance threshold), the control unit logs a 'high resistance' fault.

During a collision, this fault may prevent or delay front passenger airbag deployment, severely compromising occupant passive safety.

High resistance in the ignition circuit causes this fault.

Potential root causes include poor contact, oxidized wiring, loose connectors, or an aging squib inside the airbag module.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

Worn clock spring carbon brushes caused intermittent high resistance

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A 2018 Qin EV450's instrument cluster airbag warning light illuminated intermittently, logging DTC B161C-00. The fault appeared on cold starts and occasionally cleared when warm. Technicians measured the passenger airbag circuit resistance and found it fluctuating between 8-15Ω when cold, returning to normal once warm. Removing the steering wheel to inspect the clock spring, they found black carbon dust buildup on the internal slip rings and severe carbon brush wear. After replacing the clock spring (part number: K9HS-3463100), resistance returned to 2.3Ω and the fault cleared. The clock spring grease had dried out after prolonged use, causing poor contact between the carbon brushes and slip rings and resistance drift.
BYD DTC AI Analysis

Airbag connector terminal oxidation increased contact resistance.

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2017 BYD Qin 100. After driving through water, the airbag warning light remained on and logged DTC B161C-00. Inspection found visible water stains inside the passenger side airbag connector (located on the right side of the dashboard), with terminals showing green oxidation. After cleaning the connector with electronic cleaner and sanding the terminals with fine sandpaper, the resistance still measured 5.8Ω. Replacing the airbag harness connector with a new one (with waterproof seal) cleared the fault. Check the A-pillar drain holes for blockages to prevent further water ingress.
BYD DTC AI Analysis

Passenger airbag module internal squib aging

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2017 Qin EV300. Airbag warning light on at 80,000 km, DTC B161C-00. Measured airbag circuit resistance: infinite (open circuit). Resistance intermittently returned to normal after shaking the airbag module. Disconnected the clock spring and measured directly at the airbag module connector; resistance was unstable. Diagnosed as a dry solder joint on the internal igniter pins or moisture in the propellant. Replaced the passenger airbag module (part number: K9HS-5334100) and completed configuration coding; the system returned to normal. Dispose of the old airbag module according to dangerous goods recycling procedures.
BYD DTC AI Analysis

Worn wiring harness behind the dashboard causing high resistance

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After accident repairs, DTC B161C-00 appeared. Inspection found improper dashboard removal and installation during the crash repair had trapped the passenger airbag harness against the dashboard metal bracket. The insulation chafed through and copper wires partially fractured, leaving only 2–3 strands connected. This ‘nearly broken’ state increased circuit resistance to 12 ohms. Repaired the damaged harness using 0.5mm² high-temperature wire, soldered joints, and double-layer heat-shrink insulation. Rerouted and secured the harness to maintain over 20mm clearance from metal edges. Fault cleared.
Other Atto 8 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.