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) — Seal U

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 — Seal U
  • 1Worn or split SRS control module wiring harness insulation causes the CAN-H or CAN-L wire to short directly to a power wire (constant or ignition power). Common locations include under the steering column, near the seat slide rails, or at bends in the sill wiring harness.
  • 2Vehicle wading, a blocked sunroof drain tube, or washing the interior with a high-pressure washer causes water ingress into the SRS control module connector (usually located under the lower center console or beneath the center armrest), resulting in an electrolytic short circuit between pins.
  • 3Improper wiring harness routing during collision repairs or unauthorized aftermarket installations (such as dash cams, seat heaters, or audio systems) allows instrument panel brackets, seat mounting bolts, or metal trim edges to cut the harness, causing a short circuit to the body 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 bumpy 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. Confirm U1005 is a current fault (Active) and will not clear. 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 (usually located under the centre console or centre tunnel). Use a multimeter to measure the resistance from the connector's CAN-H (orange/black) and CAN-L (orange/brown) terminals to the battery positive terminal. Normal resistance is greater than 1 MΩ. A resistance below 10 kΩ confirms a short circuit.
  • 3
    If resistance is abnormal, troubleshoot in sections: disconnect the airbag coil (clock spring) connector, the seatbelt pretensioner connector under the seat, and the side impact sensor connector. Measure each section to isolate the short circuit. Carefully inspect the wiring harness bends below the steering column and the wiring harness protective sleeve near the seat slide rail.
  • 4
    Check the SRS control module connector pins for push-out, corrosion, burn marks, or signs of water ingress. Clean with electrical contact cleaner and blow dry. If necessary, replace the connector or repair the pins.
  • 5
    If the wiring harness appears normal and sectional measurements show no short circuits, reconnect the battery with the SRS module disconnected. Measure the voltage between the harness-side CAN wires and ground. A 12V reading indicates a shorted 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, maintaining a minimum 20 mm clearance from metal edges. Restore all connections, clear the fault code, and perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times) to verify 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

✓
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 Seal U 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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.