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U058508

DTC U058508 indicates abnormal CAN communication data between the IPB (Intelligent Integrated Braking System) and the TCU (Transmission Control Unit) — Atto 3

Braking System

DTC U058508 indicates abnormal CAN communication data between the IPB (Intelligent Integrated Braking System) and the TCU (Transmission Control Unit).

Specifically, the TCU data frames received by the IPB contain checksum errors, implausible data logic, or communication timeouts.

This fault affects critical data exchange between the powertrain and braking systems.

The TCU cannot provide the IPB with accurate gear state, torque request, motor speed, or vehicle speed signals, preventing the braking system from coordinating the switching logic between energy recovery and hydraulic braking.

Potential causes include corrupted internal TCU EEPROM data, CAN bus physical layer interference, logic errors resulting from an abnormal TCU power supply, or parsing errors at the IPB receiver.

When triggered, this fault may limit vehicle power output, disable the energy recovery function, and illuminate the ABS/ESC warning light.

In severe cases, the vehicle enters Limp Home Mode.

3
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i: TCU data abnormality caused braking system warning

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Vehicle: 2021 Song Plus DM-i, 32,000 km. Symptoms: While driving, the instrument cluster suddenly displayed "Check Braking System" and "Check Transmission System". The ESC and ABS warning lights illuminated and the energy recovery function failed. Diagnosis: Scanned with VDS2000 and retrieved U058508 (TCU data corrupted) and U059508 (MG communication data abnormal). TCU power supply was normal. Measuring CAN line resistance revealed 2 MΩ between CAN-H and ground on the TCU-IPB circuit (abnormally low). Further inspection found a loose wiring harness clip at the firewall. The CAN-H line insulation had chafed through against a metal bracket, causing intermittent shorts to ground after driving in rain. This caused the IPB to fail validation of TCU data frames. Solution: Repaired the damaged CAN-H wiring, insulated it with double-layer heat-shrink tubing, and re-secured the harness routing to prevent contact with the body. Cleared the fault codes and test-drove 200 km with no recurrence.
BYD DTC AI Analysis

Qin Pro DM: TCU program error causing abnormal communication data

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Vehicle: 2019 BYD Qin Pro DM, 58,000 km. Symptoms: Cold start normal. After 15–20 minutes of driving, the instrument cluster displays "Transmission function limited" and sets DTC U058508. The vehicle enters limp mode and can only drive at low speed in pure EV mode. Diagnosis: The fault only appears after TCU temperature rises. Initially suspected TCU hardware. TCU power and ground tested normal. CAN waveform normal when cold, but showed intermittent noise when hot. Found BYD technical service bulletin (TSB-2020-03): this TCU batch has a software bug. Under high temperatures, EEPROM data reads incorrectly, causing transmitted gear signals to exceed valid ranges; the IPB flags this as data corruption. Solution: Upgraded TCU software to V2.3.5. After upgrading, conducted a continuous one-hour road test. No fault occurred even when TCU temperature exceeded 75°C. Fault resolved.
BYD DTC AI Analysis

Water ingress in Song DM TCU connector caused data communication error

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Vehicle: 2020 Song DM, 41,000 km, accident-damaged and repaired. Symptoms: After front-end repairs, multiple warning lights flashed on the instrument cluster at startup. Scan tool retrieved U058508 and multiple communication faults. Diagnosis: Found front compartment wiring harness damage from the accident. The TCU connector (located at the left front fender liner) had a broken seal cap latch. Recent rain exposure allowed water into the connector; pins 6 (CAN-H) and 7 (CAN-L) showed electrochemical corrosion, causing CAN signal impedance mismatch. The IPB could not correctly parse data frames from the TCU. Repair: Replaced the TCU connector assembly (includes wiring harness Repair Kit), wrapped it with specialized waterproof tape, replaced the damaged seal ring, cleaned the TCU socket with WD-40 Precision Electrical Cleaner, and cleared fault codes. Communication returned to normal.
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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.