AU
C080002

This DTC indicates the ABS (Anti-lock Braking System) electronic control unit detects an operating supply voltage outside the calibrated allowable range (typically 9 — Seal U

Braking System

This DTC indicates the ABS (Anti-lock Braking System) electronic control unit detects an operating supply voltage outside the calibrated allowable range (typically 9.5V-16V).

In the BYD E5, the 12V low-voltage system powers the ABS module.

The DC-DC converter steps down voltage from the high-voltage battery pack to provide this supply.

If the module detects voltage that is too high (>16V, risking internal ECU circuit damage) or too low (<9V, reducing control accuracy), it logs DTC C080002.

This condition may trigger system protection mechanisms, causing ABS, EBD, ESC, and Automatic Emergency Braking functions to fail or enter a degraded mode.

Troubleshoot this fault immediately, as it affects braking safety.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 112V low-voltage battery aging, sulfation, or internal short circuit causes voltage fluctuations or increased internal resistance, resulting in a sudden voltage drop during high-current loads such as ABS pump motor operation.
  • 2DC-DC converter fault: Output voltage regulation failure causes excessive (>15V) or unstable low-voltage system voltage.
  • 3Poor contact, oxidized or loose terminals, or a burned fuse holder in the ABS module power supply circuit (constant power B+, ignition power IG1), causing excessive circuit voltage drop.
  • 4Main body ground point (usually near the left front longitudinal rail or battery tray) corroded or loose, causing ABS module reference ground potential drift.
  • 5ABS hydraulic modulator internal power management circuit or voltage monitoring chip failure, causing false faults or failure to adapt to normal voltage fluctuations.
What To Do
  • 1
    Connect the diagnostic tool and read the DTC freeze frame data. Confirm the specific voltage value when the fault occurred (to determine if it is a high-voltage or low-voltage fault) and related information such as vehicle speed and ABS pump operating status.
  • 2
    Measure the 12V battery static voltage (standard 12.4V-12.6V) and load voltage (turn on headlights and air conditioning; must be >12.0V). Use a battery tester to check the CCA value and internal resistance to determine whether to replace the battery.
  • 3
    Check the DC-DC converter output voltage (standard 13.8V-14.2V). Use an oscilloscope to monitor voltage fluctuations and check for voltage spikes or drops.
  • 4
    Inspect the ABS module power connector (B25 plug) terminals for backed-out pins or burning. Measure the voltage drop at power terminals 1/32 (B+) and 31/16 (IG1) (should be <0.5V). Check the 30A ABS fuse and power relay.
  • 5
    Check the ABS module ground point (G106, usually located on the left front suspension strut tower or longitudinal beam). Remove the ground wire and sand the contact surface. Measure the ground resistance (should be <1Ω) to eliminate a poor connection.
  • 6
    Inspect the wiring harness insulation for damage to rule out a short to the body or an intermittent open circuit. Focus on the wiring harness protection in high-temperature areas of the engine compartment.
  • 7
    If wiring and power supply are normal, update the ABS module software (if an update is available). If ineffective, replace the ABS hydraulic modulator assembly with ECU, bleed the system, and calibrate the sensors.
Real-World Cases
BYD DTC AI Analysis

E5: ABS warning light intermittently on while driving; 12V battery aged

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Vehicle: 2018 BYD E5, 80,000 km. Symptoms: ABS warning light illuminates intermittently while driving. DTC C080002 (Voltage out of range). Freeze frame shows 11.2V at time of fault. Diagnosis: 12V battery static voltage measured 12.3V, dropping to 11.5V with AC on. Load test: CCA only 40% of rated value, internal resistance 8.5mΩ (excessive). DC-DC output reads 14.0V (normal). Aged battery causes voltage sag when ABS pump operates. Solution: Replaced 12V battery (12V 60Ah). Cleared fault codes; one month follow-up shows no recurrence.
BYD DTC AI Analysis

DC-DC converter output voltage too high caused C080002

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Vehicle: 2019 E5, post-accident repair. Symptoms: ABS and ESP lights on constantly after startup, DTC C080002. Diagnosis: Data stream showed ABS supply voltage at 16.8V, far above normal. DC-DC output also 16.8V; internal voltage regulation circuit fault, likely from accident damage. ABS module undamaged. Solution: Replaced DC-DC converter assembly (integrated with high-voltage distribution box), recalibrated low-voltage system, fault resolved.
BYD DTC AI Analysis

Loose connection at ABS module power connector caused intermittent fault

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Vehicle: 2018 E5, 120,000 km. Symptom: ABS warning light illuminates when driving on rough roads; normal on flat roads. Diagnosis: DTC C080002 stored as history code. Battery and DC-DC converter tested normal. Inspection of ABS module connector B25 revealed burn marks on terminal 1 (constant power B+) and internal looseness. Long-term vibration increased contact resistance, causing voltage drop under high current. Solution: Replaced ABS module power connector (repair kit), re-crimped terminals, applied conductive grease. Fault eliminated.
BYD DTC AI Analysis

Corrosion at body ground point caused voltage fault

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Vehicle: 2019 E5, coastal use. Symptom: ABS warning light on after rain or washing; DTC C080002. Diagnosis: ABS module power supply voltage normal, but resistance between module ground and body measured 3.2Ω (spec <1Ω). Found left front longitudinal beam ground point G106 severely corroded with loose bolt. Cause: Seawater corrosion caused poor ground and reference ground potential drift. Repair: Sanded ground point to bare metal, installed stainless steel ground bolt, retightened, and applied anti-rust paint. Fault cleared.
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.