AU
U1005

DTC U1005 indicates the vehicle SRS (Supplemental Restraint System/airbag system) control module detects a short circuit between its CAN communication bus (including CAN-H and/or CAN-L lines) and the vehicle positive power supply (12V battery voltage or high-voltage system power supply) — Atto 8

Safety System

DTC U1005 indicates the vehicle SRS (Supplemental Restraint System/airbag system) control module detects a short circuit between its CAN communication bus (including CAN-H and/or CAN-L lines) and the vehicle positive power supply (12V battery voltage or high-voltage system power supply).

Normally, the CAN bus voltage to ground measures approximately 2.5V (recessive state) and 3.5V/1.5V (dominant state).

A short to power pulls the CAN bus voltage up to 12V, completely interrupting communication between the SRS system and the vehicle Powertrain CAN or Body CAN.

Because safety-critical subsystems (airbag system, seat belt pretensioners, crash sensors, and seat occupancy detection) rely on the CAN bus for data exchange and trigger command transmission, this fault prevents the airbag system from deploying normally during a collision.

This constitutes a Level 1 severe fault affecting occupant life safety.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Worn or split insulation on the SRS control module wiring harness causes the CAN-H or CAN-L wire to short directly to a power wire (constant or ignition power). This commonly occurs below the steering column, near the seat slide rails, or at bends in the sill wiring harness.
  • 2Vehicle wading, a blocked sunroof drain hose, or high-pressure washing of the interior caused water ingress at the SRS control module connector (usually located under the lower center console or beneath the center armrest box), resulting in an electrolytic short circuit between the pins.
  • 3During accident repairs or unauthorized aftermarket modifications (e.g., dash cams, seat heaters, audio systems), improperly securing the wiring harness allows the instrument panel bracket, seat mounting bolts, or metal trim edges to cut the harness, causing a short circuit to the vehicle power supply.
  • 4Damaged internal CAN transceiver integrated circuit in the SRS control module. An internal short circuit pulls the CAN line voltage high. Module overheating usually accompanies this fault.
  • 5Instrument panel or floor wiring harness insulation cracked due to long-term aging, contacting the power distribution box or fuse box metal bracket on rough roads and causing a short circuit.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000/3000) to read all fault codes and freeze frame data. Verify U1005 is a current fault (Active) that will not clear, and check for accompanying B1xxx series SRS sensor faults or U01xx communication faults.
  • 2
    Perform the high-voltage power-down procedure (for new energy vehicles) or disconnect the 12V battery negative terminal. Wait 3 minutes for the capacitors to discharge, then disconnect the SRS control module connector (typically under the center console or center tunnel). Use a multimeter to measure the resistance from connector terminals CAN-H (orange/black) and CAN-L (orange/brown) to the battery positive terminal. Normal resistance is greater than 1 MΩ. A resistance below 10 kΩ indicates a short circuit.
  • 3
    If resistance is abnormal, troubleshoot in sections: disconnect the airbag coil (clock spring) connector, the seat belt pretensioner connector under the seat, and the side impact sensor connector. Measure each section to isolate the short circuit. Focus inspection on the wiring harness bend below the steering column and the harness protective sleeve near the seat slide rail.
  • 4
    Check the SRS control module connector pins for push-out, corrosion, burn marks, or water ingress. Clean with electrical contact cleaner and blow dry. Replace the connector or repair the pins if necessary.
  • 5
    If the wiring harness appears normal and sectional testing shows no short circuits, reconnect the battery (do not connect the SRS module). Measure the CAN wire-to-ground voltage at the harness end. A 12V reading indicates a short circuit in the CAN transceiver inside the SRS control module. Replace the SRS control module and perform coding configuration.
  • 6
    After repairing the short circuit, wrap the damaged area with dual-wall heat-shrink tubing or insulating tape. Re-secure the wiring harness to maintain a clearance of more than 20mm from metal edges. Restore all connections. Clear the fault code and perform the SRS system self-check cycle (ignition switch ON-OFF three times) to confirm the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM SRS Light On, U1005 Fault After Driving Through Water

✓
2021 BYD Tang DM displayed "Please check SRS system" after wading through heavy rain. Retrieved DTC U1005. Inspection found water in the SRS module connector under the centre console. Disassembly revealed the sunroof drain hose had detached, letting water into the cabin. Electrolytic corrosion caused the CAN-H pin to short to the adjacent constant power pin. Cleared the standing water, cleaned the connector with electrical contact cleaner, repaired the corroded pins, reinstalled the drain hose. Resolved.
BYD DTC AI Analysis

Airbag warning light stays on after accident repair – Yuan EV

✓
After right-front collision repairs on a 2019 BYD Yuan EV, the SRS warning light stayed on. The scan tool showed U1005 CAN short to power. Inspection found the dashboard wiring harness replaced during the accident repair had been secured incorrectly; a right A-pillar trim clip crushed the harness insulation, causing the SRS CAN wire to short to the cigarette lighter power line. Technicians rewrapped the damaged harness, adjusted the routing to avoid the trim clips, and cleared the fault codes. The system returned to normal.
BYD DTC AI Analysis

Aftermarket heated seats caused CAN bus fault on Song MAX

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2019 Song MAX owner reported U1005 after installing front seat heaters at a non-authorised workshop. Inspection found the installer spliced into the SRS CAN bus when drawing power, and an internal fault in the heating pad controller backfed 12V into the CAN lines. Repair: Removed the illegal add-on wiring, restored insulation on the original harness, replaced the damaged CAN harness sections, and recalibrated the SRS module.
BYD DTC AI Analysis

Qin Pro SRS control module internal short circuit

✓
2020 Qin Pro: Intermittent SRS warning light while driving. Diagnostic tool retrieved DTC U1005, intermittent. Disconnected SRS module and measured harness resistance to power supply – normal. Measured inside module: intermittent short between CAN-H and power terminal. Disassembled module; found dry solder joint on CAN transceiver chip caused contact with power layer during thermal expansion and contraction. Repair: Replaced SRS control module (ECU), programmed vehicle VIN and configuration codes using dedicated equipment, and performed system calibration.
BYD DTC AI Analysis

Yuan Plus sill wiring harness chafed and shorted

✓
After three years of use, the vehicle threw a U1005 code. Inspection found the floor harness under the driver's seat had chafed through against the sill trim edge from repeated seat adjustments, exposing the CAN-L wire and shorting it to the seat motor power line. Fix: Repaired the damaged harness, added corrugated tubing at the sill, and repositioned the harness clips to clear moving parts.
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
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.