Guide

How to read OBD2 live data (PIDs)

OBD2 live data is the set of sensor values your car's engine computer reports in real time, requested with standard parameter IDs (PIDs). US rules require a core set, such as engine RPM, coolant temperature, calculated load, fuel trim, vehicle speed and throttle position, so any OBD2 scanner can read them.

Key facts

Key fact	Detail
What a PID is	A parameter ID used to request one value, defined in SAE J1979
Live data service	Service (mode) 01: current data
Freeze frame service	Service (mode) 02: the same PIDs, saved when a code was stored
Required by US rules	Coolant temperature, fuel system status, fuel trim, timing advance, intake air temperature, manifold pressure, air flow, RPM, throttle position, load, vehicle speed and more
Supported PIDs	Not every car supports every PID; the car reports which ones it has
Brand specific data	Manufacturers define extra, non standard PIDs

What are PIDs?

A PID is a code a scanner sends to ask the engine computer for one value, such as engine speed. The standard PIDs are defined in SAE J1979. Service 01 returns the current value; service 02 returns the same value from the freeze frame stored with a trouble code.

US regulations require OBD2 vehicles to make a standard set of engine data available through the diagnostic connector in standard units, which is why a generic adapter can read it on any compliant car.

Common PIDs and what they tell you

PID (hex)	Value	What it is useful for
04	Calculated engine load	How hard the engine is working, in percent
05	Engine coolant temperature	Whether the engine reaches and holds normal operating temperature
06, 07	Short and long term fuel trim, bank 1	Whether the computer is adding or removing fuel
0B	Intake manifold absolute pressure	Engine vacuum and load
0C	Engine RPM	Engine speed at idle and while driving
0D	Vehicle speed	Road speed as the computer sees it
0F	Intake air temperature	Temperature of the air entering the engine
10	Mass air flow rate	How much air the engine is taking in
11	Throttle position	How far the throttle is open
14 to 1B	Oxygen sensor voltage	Whether narrow band oxygen sensors switch between lean and rich
42	Control module voltage	Supply voltage seen by the engine computer

Why some values are missing

Cars only answer for the PIDs they support, and the car reports a list of supported PIDs, so a scanner asks for that list first. Not all vehicles support all PIDs. Values beyond the standard set, such as gearbox data on many cars, come from manufacturer specific PIDs.

Tips for reading live data

Let the engine reach full operating temperature before judging fuel trims or oxygen sensors.
Check the fuel system status: closed loop means the computer is using oxygen sensor feedback.
Compare readings at idle and at a steady higher rpm.
Record a short log while the problem happens, then compare it with the freeze frame of any stored code.

Live data in OBD Master Pro

OBD Master Pro shows standard OBD2 sensors such as RPM, speed, coolant temperature, load, throttle, intake air, MAF, MAP, fuel trims, O2 and battery voltage, plus brand data where your car's profile has it. You can place them on a dashboard, view live charts, record and play back logs and add custom PIDs.

Try it on your own car

OBD Master Pro turns your Android phone and a generic ELM327 adapter into a code reader: read and clear codes, view freeze frame and live data, and check emissions readiness.

Keep reading

Common codes: P0171 System Too Lean · P0420 Catalyst Efficiency · P0300 Random Misfire · P0455 EVAP Large Leak

All OBD2 guides · OBD2 by car brand · OBD2 trouble code guides

Sources

Published October 24, 2026. Updated October 24, 2026. General information only. Details generally vary by model, year and market, so always follow the owner's manual and service information for your vehicle.