AU
U1005-00

DTC U1005-00 indicates a short circuit between the Supplemental Restraint System (SRS) Controller Area Network (CAN) communication line and vehicle power (+B) — Seal U

Safety System

DTC U1005-00 indicates a short circuit between the Supplemental Restraint System (SRS) Controller Area Network (CAN) communication line and vehicle power (+B).

In BYD Qin series models, the Airbag Control Module (ACM) communicates with the vehicle network via the CAN bus.

When the CAN-H or CAN-L line shorts to constant power or ignition power, the short pulls the bus voltage up to 12V (battery voltage), distorting the CAN signal and interrupting communication.

This prevents the airbag system from receiving crash sensor signals or triggering airbag deployment, and may affect safety-related functions such as the seat belt pretensioners and the airbag warning lamp.

Because the CAN bus uses differential signal transmission, a short to power disrupts communication across the entire CAN network segment (typically including the instrument cluster and BCM).

This serious fault endangers driving safety.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Engine compartment or cabin wiring harness wear damages the insulation, causing the CAN and power wires to contact each other, especially in high-wear areas such as the firewall pass-through and under the seat rails.
  • 2Airbag Control Module (ACM) internal transceiver circuit fault; CAN pin shorted to power. Internal module component breakdown usually causes this.
  • 3After vehicle wading or heavy rain, water ingress and corrosion in SRS system connectors (such as floor harness connectors and under-seat connectors) cause a short circuit between the CAN line pins and power supply pins.
  • 4Unauthorized modifications (such as installing a dash cam, large-screen navigation, or push-button start) that mistakenly connect the CAN line to the positive power supply, or pierce the wiring harness, causing the power supply to contact the CAN line.
  • 5Improper sheet metal repair during accident repairs caused the wiring harness retaining clip to detach, leading to a short circuit from prolonged vibration and chafing against a sharp edge.
What To Do
  • 1
    Use VDS2000 or a dedicated diagnostic tool to read all fault codes. Confirm U1005-00 is a current fault, not a history fault. Check for an accompanying U1004 (CAN short to ground) or other SRS communication fault codes.
  • 2
    Disconnect the battery negative terminal and wait 3 minutes. Perform the high-voltage power-down procedure (for EV models). Remove the airbag control module (located in the center tunnel or under the dashboard). Visually inspect the connector for signs of water ingress, corrosion, or burning.
  • 3
    Use a multimeter to measure the resistance from the wiring harness side CAN-H (orange/black) and CAN-L (orange/brown) to body ground. Normal resistance is greater than 1 MΩ. Measure the resistance to +B (constant power). Normal resistance is infinite. If the resistance is less than 10 kΩ, confirm a short circuit in the wiring harness.
  • 4
    If the wiring harness insulation is normal, reconnect the battery (do not disconnect the ACM connector), turn on the ignition switch, and measure the CAN line voltage: normal CAN-H is approximately 2.5-3.5V, and CAN-L is approximately 1.5-2.5V. If the voltage is close to 12V, this indicates an internal short circuit in the ACM. Replace and recode the airbag control module.
  • 5
    If confirming a wiring harness fault, use a sectional troubleshooting method: start from the ACM connector and inspect along the floor wiring harness toward the instrument panel and crash sensor. Focus on wear-prone areas such as the firewall pass-through, under the seat slide rails, inside the A-pillar trim panel, and inside the sill wiring harness sleeve.
  • 6
    After locating the damage, repair the wiring harness (cut out the damaged section, solder, and insulate with heat-shrink tubing; do not simply wrap the repair). Check adjacent wires for damage and replace the entire wiring harness if necessary.
  • 7
    After repair, measure the CAN bus terminating resistance (Qin series SRS terminating resistance is typically 120Ω, and approximately 60Ω with the bus in parallel). Verify no short circuit exists, then reinstall all components.
  • 8
    Clear the fault code and perform an ignition cycle test. Confirm the SRS warning lamp turns off after a normal self-check. Use the diagnostic tool to confirm communication with the ACM is restored. Perform an airbag system function test.
Real-World Cases
BYD DTC AI Analysis

Qin EV300: Worn floor harness caused CAN short to power

✓
A 2017 Qin EV300 with 80,000 km displayed "Check SRS System" on the instrument cluster and the airbag warning light remained on. The scanner read DTC U1005-00. Inspection found the floor harness retaining clip beneath the driver's seat rail had detached. The harness had chafed against the seat rail, wearing through the CAN-H line insulation and shorting it to the seat heater power line (+B). Repair: Cut out the 20 cm damaged section, re-soldered and double-insulated the joint, replaced the retaining clip, and rerouted the harness clear of moving parts. This cleared the fault and restored normal communication.
BYD DTC AI Analysis

Qin 80: Airbag control module connector corroded after driving through water

✓
2017 BYD Qin 80 set DTC U1005-00 after wading through heavy floodwater, with a damp musty odour inside. Inspection found water had reached sill height. The airbag control module (ACM) connector seal under the centre console had degraded, letting water into the connector and causing electrolytic corrosion that shorted the CAN bus pins to constant power. Resolution: Disconnected the battery, thoroughly cleaned the connector terminals with precision instrument cleaner and ultrasonic cleaning, dried them with compressed air, applied conductive anti-corrosion grease, and replaced the waterproof seal. ACM internals were undamaged, so the module didn't need replacement. Also inspected and cleared the drain holes to prevent future water ingress.
BYD DTC AI Analysis

BYD Qin EV450: Aftermarket Large-Screen Navigation Triggered CAN Bus Fault

✓
A 2018 BYD Qin EV450 threw a U1005-00 code and the factory multi-function steering wheel stopped working after an aftermarket workshop fitted a third-party Android head unit. Inspection found the installer had tapped into the dashboard wiring harness CAN bus using insulation-piercing connectors to get a vehicle speed signal, but clamped the CAN-H line to the head unit's constant power (+12V), shorting the CAN bus to power. Repair: Removed the unauthorized wiring, cut out the damaged CAN section (approximately 15cm), resoldered the connections per factory wire order with proper insulation, and restored the original harness layout. Replaced the damaged CAN bus termination resistor (located in the dashboard harness). Restored the factory navigation system; fault cleared.
BYD DTC AI Analysis

Internal circuit breakdown in Qin 100 ACM caused short circuit

✓
A 2017 Qin 100 suddenly showed the airbag warning light during normal operation. Scanned U1005-00. Checked the harness—no damage or water ingress. Measured 12V on the CAN lines at the ACM connector. Disconnected the ACM and measured normal voltage (2.5V/2.3V) on the harness side. Confirmed the ACM’s internal transceiver circuit failed, shorting the CAN pins to internal power. The Qin 100’s ACM and airbag trigger IC are too highly integrated to allow separate circuit board repair. Replaced the OEM airbag control module (PN: BYD-3638100-X), coded and configured it using VDS2000, performed the airbag system calibration, and cleared the fault codes. System returned to normal.
BYD DTC AI Analysis

BYD Qin EV300: Wiring harness improperly secured after accident repair

✓
A Qin EV300 with front-end collision damage threw an intermittent U1005-00 code after dealership repairs. The crash repair replaced the instrument panel harness, but the firewall grommet was not installed correctly, letting the CAN harness contact the heater pipe bracket. Motor vibration rubbed the harness against the bracket, causing intermittent shorts to power (the bracket grounds to the body, but a nearby +12V wire had insulation damage). Fix: Reroute the instrument panel harness, secure with OEM clips, add a rubber grommet at the firewall, repair the damaged power wire insulation, and keep the harness 20mm clear of metal components. The fault has not returned.
Other Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.