Live Data Guide
Live Data (Real-Time PIDs) is a continuous stream of readings from your car’s ECU. Unlike DTCs (which record a past fault), live data shows the current state right now. Knowing how to read it saves time and money on unnecessary repairs.
How to access live data
- Connect to your adapter (Bluetooth → select adapter → Connect)
- On the main screen tap Live Data or Gauges
- Pick PID parameters from the list (or use our presets: “Basics” / “Fuel System” / “Turbo”)
- Tap Start — readings update up to 5 times per second
You can save a session and review graphs later.
Key PIDs and their normal ranges
Engine and ignition
| PID | What it measures | Normal range (warm engine) |
|---|---|---|
| RPM | Engine speed | Idle: 700-900 RPM |
| ECT (Engine Coolant Temp) | Coolant temperature | 185-205°F / 85-95°C |
| IAT (Intake Air Temp) | Intake air temperature | Ambient ± 18°F / 10°C |
| Load (Calculated Engine Load) | Engine load percentage | Idle: 15-35%; WOT: 80-100% |
| TPS (Throttle Position) | Throttle opening | At rest: 0%; Pedal to floor: 100% |
Fuel system
| PID | What it measures | Normal range |
|---|---|---|
| STFT B1/B2 | Short Term Fuel Trim | −10% … +10% |
| LTFT B1/B2 | Long Term Fuel Trim | −10% … +10% |
| O2 S11 | Upstream O2 sensor voltage | Should oscillate 0.1-0.9V (closed loop) |
| MAF | Mass Airflow | Idle: ~3-7 g/s depending on displacement |
| MAP | Intake Manifold Pressure | Idle: ~25-45 kPa (atmosphere ~101 kPa) |
Reading fuel trim
LTFT > +10% — ECU is adding fuel persistently. Mixture is lean. Look for: vacuum leak, dirty MAF, weak fuel pump, failing O2 sensor.
LTFT < −10% — ECU is cutting fuel persistently. Mixture is rich. Look for: leaking injectors, excessive fuel pressure, stuck-open EVAP purge valve.
STFT swings ±15% — mixture is unstable. Sign of an intermittent vacuum leak or a dying O2 sensor.
Live data for specific systems
Turbocharger
- Boost Pressure (or MAP in positive pressure): normal under load depends on the car, typically 12-22 PSI / 0.8-1.5 bar gauge
- Wastegate Duty Cycle: percentage opening of the bypass valve
- Boost lower than spec at WOT → intercooler leak, worn actuator, or restricted VNT vanes
ABS and wheel sensors
- WSS FL/FR/RL/RR (Wheel Speed Sensors): all 4 should show identical speed on a straight; >1-2 mph deviation at constant speed = suspect worn wheel bearing or bad sensor
Automatic transmission
- ATF Temp: should stay under 190°F / 90°C in normal driving; above 230°F / 110°C is overheating
- Gear Position: shows the current gear
- TCC Status: torque converter lock-up clutch status
Tips for effective data logging
Log while driving, not parked. Most problems appear under load — pick a safe straight road where a passenger can monitor readings while you drive.
Use the Snapshot feature. If you see an anomaly — tap the Snapshot button in the app. All current values are saved with a timestamp.
Compare over time. A single reading tells you little. Compare readings a week apart, or before and after a repair — that’s where live data becomes powerful.
Don’t monitor more than 5-6 PIDs at once. Each parameter is a separate AT command to the adapter. More than 6-8 PIDs reduces the update rate and may overwhelm the adapter.