Yaris HV Battery Cooling Fan Optimizer — CAN/OBD-II Telemetry
Native Android telemetry and ECU coding application developed in Kotlin and Jetpack Compose for the Toyota Yaris MK4 (XP210 series, M15A-FXE). Interfaces with vehicle ECUs via Bluetooth Low Energy (BLE) OBD-II adapters using ISO 15765-4 CAN 500k and UDS diagnostic protocols. Features automatic battery pack thermal derating prevention, manual Denso fan override (Level 6), Dragy 0-100 sprint timing, and customizable cabin/ADAS ECU codings.
Overview & Automotive Challenge
The Toyota Yaris MK4 Hybrid (XP210) employs a 4.3 Ah lithium-ion battery pack cooled by a dedicated Denso centrifugal blower fan. Under sustained highway climbs or hot summer conditions (>30°C ambient), battery cell temperatures routinely exceed 36°C–38°C, triggering OEM thermal protection routines that drastically throttle EV electric motor assistance and regenerative braking efficiency.
3-Tab Architectural Hierarchy
The application is structured into three dedicated functional modules operating over a background ForegroundService with zero telemetry starvation:
| Module | Core Technology | Automotive Capabilities |
|---|---|---|
| 🏁 Cockpit | Dragy Engine & High-Speed CAN | Large digital speedometer (PID 010D), ignition advance (PID 010E), engine load (PID 0104), and Dragy 0–50 / 0–100 km/h sprint timing with persistent PB storage. |
| 🌀 Fan Control | Denso UDS IO Control & ISO-TP | Continuous trigger threshold (28.0°C–42.0°C), hysteresis band (1.0°C–5.0°C), manual Level 6 MAX override, and 4-probe module array monitoring (PID 2228C1). |
| 🛠️ ECU Coding | Multi-ECU UDS Configuration | Customization of Toyota Touch 3 startup animations (GR / HSD), reverse single-beep comfort mode, speed-sensing central locking, and ADAS sensitivity. |
*Table 1: Yaris HV Fan Optimizer Application Architecture*
// Automated battery cooling fan IO control dispatch in Kotlin
suspend fun dispatchFanSpeedOverride(fanLevel: Int): Result<ByteArray> {
require(fanLevel in 0..6) { "Fan level must be between 0 and 6" }
// UDS Diagnostic Service 0x2F (InputOutputControlByIdentifier)
// Parameter: 0x5803 (Battery Blower Fan Control), Option: 0x03 (ShortTermAdjustment)
val udsPayload = byteArrayOf(0x2F.toByte(), 0x58.toByte(), 0x03.toByte(), fanLevel.toByte())
return obdController.sendRawEcuFrame(targetEcu = EcuAddress.BATTERY_7E2, payload = udsPayload)
}Standalone Diagnostic Bridge (:sniffer)
The project includes an integrated reverse-engineering utility (Yaris OBD Bridge) distributed as an independent APK. It binds a local TCP socket server on 127.0.0.1:35000, acting as a man-in-the-middle diagnostic sniffer for third-party tools (Dr. Prius, Car Scanner) with millisecond-accurate timestamp logging.
Automated Verification & Test Coverage
- 100% Passing Test Suite: Over 90 automated unit and integration tests across ISO-TP frame reassembly, ELM327 parser resilience, candidate cooldown state machines, and zero-starvation engine invariants.
- Supported Adapters: Vgate iCar Pro BLE 4.0+, vLinker MC+/FD+ (recommended for multi-frame ISO-TP), Veepeak OBDCheck BLE, and Carista OBD.