AU
B161C

DTC B161C indicates the SRS (Supplemental Restraint System) ECU detects the front passenger frontal airbag ignition circuit resistance exceeds the calibrated upper limit (typically >5Ω) — Atto 3

Safety System

DTC B161C indicates the SRS (Supplemental Restraint System) ECU detects the front passenger frontal airbag ignition circuit resistance exceeds the calibrated upper limit (typically >5Ω).

Normal airbag igniter resistance is between 2.0Ω and 3.0Ω.

Excessive resistance indicates high resistance or an open circuit risk in the ignition circuit.

This prevents the ECU from supplying sufficient ignition current (typically 1.2A or higher) during a collision, causing the front passenger airbag to fail to deploy and severely compromising passive safety.

This is a hard fault.

The system illuminates the airbag warning lamp and disables the front passenger airbag.

Inspect and repair immediately.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Poor contact at pins 1 and 2 of front passenger airbag module connector X246 (located on the right side of the instrument panel crossmember), or black locating clip not fully seated (standard requirement: the top of the clip must sit below the terminal mating face).
  • 2A poor connection, oxidation, terminal back-out, or spread terminals in the wiring between the instrument panel wiring harness and the airbag module cause increased contact resistance.
  • 3Aging, moisture ingress, or an internal open circuit in the front passenger airbag module squib causes increased resistance.
  • 4Prolonged parking in a high-humidity environment or driving through water caused internal connector corrosion, forming an oxide layer.
  • 5SRS ECU internal sampling resistor or A/D conversion circuit fault (intermittent incorrect resistance reading; rule out through cross-validation).
What To Do
  • 1
    Safety preparation: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the passenger-side lower dashboard trim panel and glove box. Locate airbag module connector X246. Check if the black locking tab sits lower than the terminal (flush or higher indicates incorrect installation). Confirm no looseness, backed-out pins, or signs of water ingress.
  • 3
    Resistance measurement: Disconnect connector X246. Use a digital multimeter to measure the resistance between the terminals on the airbag module side. The standard value is 2.0Ω-3.0Ω. If the resistance is >5Ω or infinite, the airbag module has an internal fault. Replace the airbag module.
  • 4
    Circuit continuity test: Measure continuity between harness side X246-1 and the corresponding SRS ECU pin, and between X246-2 and ground. Circuit resistance must be <1Ω. Gently shake the harness to check for intermittent open circuits.
  • 5
    Connector repair: If poor contact exists, clean the pins with electrical contact cleaner and apply conductive grease. Use the dedicated terminal release tool to repair the terminal retaining spring. Reinstall the connector. Verify the locking tab engages fully and the insertion/withdrawal force is >50N.
  • 6
    System verification: Connect the battery, use the VDS or ED300 diagnostic tool to clear the fault code, and perform an SRS system self-check (3 key cycles or a drive cycle). Confirm B161C does not return and the warning lamp turns off. Read the data stream to confirm the front passenger airbag resistance is 2.0-3.0 Ω.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin: Poor contact at the X246 connector caused fault code B161C

✓
Symptoms: Airbag warning light stayed on after 3000 km, displaying a flash code: 5 seconds on, 7 flashes. Diagnosis: Connected the ED300 diagnostic tool and retrieved DTCs B161C (passenger airbag resistance too high) and B1610 (passenger airbag not connected). Isolated the fault to the passenger airbag module wiring harness, connector, or SRS ECU. Inspection: Checked the connection between the passenger airbag module pigtail and the instrument panel harness. Found poor contact at pins 1 and 2 of connector X246; the black retaining clip did not seat properly (the clip must sit below the terminal—flush or protruding indicates incorrect installation). Solution: Reassembled and secured pins 1 and 2 at X246, ensuring the black retaining clip seated properly below the terminal. Road tested after reassembly and the fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Standard Diagnostic Procedure for SRS High Resistance – BYD Qin/Song/Yuan

✓
Symptoms: Dashboard airbag warning light stays on. DTC B161C-00 (front passenger airbag resistance high). Diagnosis: Per BYD Qin sedan workshop manual, B161C-00 indicates front passenger airbag resistance high. Diagnostic procedure: 1. Inspect front passenger airbag module and wiring harness connections. 2. Check connector X246 between the instrument panel harness and the airbag module (located on the instrument panel crossmember behind the glovebox). 3. Measure airbag module resistance. Normal resistance falls within specification (typically 2–5 ohms). High resistance indicates poor circuit connection or an internal airbag module fault. 4. Inspect connector pins for oxidation, looseness, or backing out. Repair: 1. Disconnect and reconnect the front passenger airbag module connector; secure it and ensure proper pin contact. 2. If the connector checks out okay but resistance remains high, replace the front passenger airbag module. 3. Clear fault codes and road test to verify.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Yuan EV front passenger airbag module internal igniter aging

✓
Symptoms: Intermittent airbag warning light on a 2019 Yuan EV at 50,000 km. Scanned DTC B161C (resistance too high). Diagnosis: Checked X246 connector; visually normal and secure. Measured wiring harness continuity at less than 0.5 Ω. Disconnected the airbag module and measured 8.5 Ω internal resistance, exceeding the 2–3 Ω specification. Determined the airbag module's internal igniter had aged, causing resistance drift. Fix: Replaced the genuine front passenger airbag module (part number varies by configuration). Post-replacement resistance 2.3 Ω. Reassembled components, cleared the fault code, and performed a crash simulation test with a resistive load substitute to confirm normal system operation.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM dashboard wiring harness pin backed out fault

✓
Symptoms: The airbag warning light on the 2021 Tang DM illuminates intermittently on rough roads and extinguishes when stationary. Retrieved historical DTC B161C. Diagnosis: Found intermittent fault. Removed the glovebox and inspected X246 connector. Pin 2 slightly backed out (~1 mm). Vehicle vibration caused poor contact with transient high resistance. Multimeter read normal resistance at rest, but the reading jumped above 10 Ω when moving the harness. Resolution: Used special terminal removal tool M101 to extract the terminal, repaired the contact spring tension, and reinserted it until an audible click confirmed lock. Measured mating force >50 N, meeting standard. Fault completely resolved.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself. Sources: [1]