Based on OBD II Standard PIDs

PID(hex) 11 Throttle Position value from 0~100%

How could we use this data to predict if there is going to be a problem?


  • What data do you have? What symptoms do you have? What car do you have? vtc as this is just a link...
    – Solar Mike
    Mar 17, 2020 at 7:11
  • I just wanna to create a general method to detect the relevant problems
    – Sean
    Mar 17, 2020 at 10:06
  • Welcome to Motor Vehicle Maintenance & Repair! Please take a moment to take The Tour as well as read through the Help Pages. Mar 17, 2020 at 11:52

1 Answer 1


By using OBD to get some key data, I developed a method to detect "throttle" related emission problems.

=== Background ===

The engine of the vehicle goes into the idle state (engine speed > 0, vehicle speed = 0) when waiting for the traffic lights. If the engine does not obtain enough air because of a throttle related problem (but not worse enough to flameout), then ECU will control to inject less fuel to maintain an Air/Fuel rate. The engine speed will drop (a small or big variation).

enter image description here

=== Method ===

  1. monitoring the "engine speed" —— to detect the abnormal variation
  2. check the changing rate of the "throttle position" —— to check if the throttle is getting stuck somehow

=== About the Maths ===

S - engine speed

T - target idle RPM

e - variation tolerance of engine speed during the idle state

if | S - T | > e, then the idling engine speed is not stable

p - throttle position

t - time

R - the changing rate of the "throttle position"

R = ΔP/Δt

if | R_max - R_median | > e during a period of time,

then we could say that R is not stable, which means, he throttle is getting stuck somehow

=== Data collected from OBD ===

  1. engine speed
  2. vehicle speed
  3. throttle position

=== welcome to post your thinking ===

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.