AU
C108008

C108008 indicates the Hill Hold Control (HHC) system detects an abnormal clutch/start interlock signal — Atto 8

Braking System

C108008 indicates the Hill Hold Control (HHC) system detects an abnormal clutch/start interlock signal.

In the BYD E5 battery electric vehicle, this fault does not refer to a conventional mechanical clutch.

Instead, it indicates the ABS/ESP control unit fails to receive the correct brake pedal-gear interlock logic signal (the combined signal the system uses to determine if the vehicle is in a 'ready to move off' state).

The HHC system relies on the brake switch signal, gear position signal (P/R/N/D status), and wheel speed signals.

When the control unit detects a released brake pedal while the gear signal or brake interlock signal contradicts the hill hold release logic, it logs a clutch signal fault.

This fault disables the hill start assist function.

The vehicle may roll backward on a slope when the driver transitions from the brake pedal to the accelerator pedal.

The fault also illuminates the ABS/ESC fault warning lamp and compromises driving safety.

The C108008 fault code on the Atto 8 indicates a medium-severity Hill Hold Control fault caused by an abnormal brake/gear interlock signal. Hill start assist may be disabled, increasing rollback risk on slopes and triggering ABS/ESC warnings. Common causes include a faulty or misaligned brake pedal position sensor or an abnormal gear selector position signal. Have the vehicle checked by an authorised dealer. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Poor contact, burnt internal contacts, or misaligned installation of the brake pedal position sensor (brake switch), causing an intermittent signal or abnormal voltage.
  • 2Abnormal signal from the gear selector position sensor (especially the P-gear lock switch); fails to correctly indicate the Neutral/Drive position status.
  • 3Loose wiring harness connectors, oxidation due to water ingress, or backed-out pins between the ABS/ESP control unit and the brake switch or gear position sensor, interrupting signal transmission.
  • 4Internal signal processing circuit fault in the ABS pump assembly; fails to correctly interpret the brake and gear position logic combination signal.
  • 5Excessively low vehicle low-voltage battery voltage (below 11V) or power supply system fluctuations cause logic errors during control unit signal acquisition.
What To Do
  • 1
    Connect the BYD dedicated diagnostic tool (VDS or ED-400), read the freeze frame data for DTC C108008, and record the vehicle speed, brake pedal status, gear position, and longitudinal acceleration value when the fault occurred.
  • 2
    Visually inspect the brake pedal position sensor (brake light switch) mounting. Check the wiring harness connector for looseness or disconnection. Measure the switch continuity and voltage signal with the pedal pressed and released (voltage normally switches between 12V/B+ and 0V).
  • 3
    Check the gear position sensor connector below the gear selector mechanism. Measure the resistance and voltage of the P-gear lock signal and gear position signal. Verify the signal output in P, R, N, and D gears meets the workshop manual standard values.
  • 4
    Disconnect the ABS pump assembly connector (located on the right side of the engine compartment or near the front compartment power distribution box). Check the terminals for oxidation, water ingress, or deformation. Measure the continuity of the brake switch signal wire and gear position signal wire to the ABS control unit (should be less than 1Ω) and the insulation resistance to ground (should be greater than 10MΩ).
  • 5
    Check the vehicle low-voltage battery voltage and charging system. Verify the static voltage is not lower than 12.4V and the dynamic voltage is not lower than 13.5V to rule out low supply voltage as the cause of abnormal signal acquisition.
  • 6
    If circuit measurements are normal, perform an ABS/ESP control unit software update or parameter reset (if supported). If the fault persists, replace the ABS pump assembly (integrated ESP control unit).
  • 7
    After repairing or replacing the faulty component, clear the fault code and verify the HHC function on a slope greater than 3%: depress the brake pedal and shift to D, release the brake pedal, and confirm the vehicle remains stationary for 2-3 seconds without rolling backward and no fault light illuminates.
Real-World Cases
BYD DTC AI Analysis

E5: Oxidised brake switch contacts caused intermittent HHC failure

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2019 BYD E5, 42,000 km. Dash intermittently showed ABS and ESC warning lights. Read fault code C108008. Inspection found the brake pedal position sensor (four-wire brake switch) had slightly burnt internal contacts, causing 0.3–0.5 s signal dropouts on rough roads. Replaced the brake switch assembly. Read the brake pedal signal data stream; cycled the pedal 20 times with normal switching. Tested HHC hill-start assist on a slope; function restored. Fault resolved.
BYD DTC AI Analysis

E5 front compartment wiring harness chafed through, causing clutch signal short circuit

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2018 E5 taxi, 80,000 km, ABS warning light on continuously, DTC C108008 would not clear. Inspection found the wiring harness below the ABS pump connector rubbing against the front compartment bracket, with the brake switch signal wire insulation worn through and shorted to ground. This caused the ABS control unit to continuously receive an incorrect brake-applied signal. Repaired the damaged harness, re-wrapped and rerouted the wiring to eliminate interference, cleared the fault code, and restored normal operation.
BYD DTC AI Analysis

E5 Gear Position Sensor Drift Caused HHC Signal Fault

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A 2019 E5 rolled back during a hill start, with the dashboard displaying 'Check Braking System'. The scan tool read DTC C108008. Live data showed the gear position signal fluctuating between N and D when Drive was engaged. Disassembling the shift mechanism revealed the gear position sensor mounting screws had loosened, allowing the sensor to shift relative to the shift shaft. Recalibrating the sensor and tightening the screws stabilized the signal and resolved the fault.
BYD DTC AI Analysis

E5: Low-voltage battery discharge caused abnormal signal acquisition

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2018 E5 started after one week parked. Multiple warning lights illuminated: ABS, ESC, and powertrain system. Retrieved DTC C108008 and multiple communication fault codes. Low voltage battery measured 10.8V. Voltage returned to normal after charging. Cleared fault codes; C108008 did not reappear. Diagnosed as discharged battery causing ABS control unit voltage drop at startup, falsely detecting abnormal brake signal. Recommended owner replace the aging battery.
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.