I am trying to to write an app which advises the driver to change gears and do some other driving quality assessments. For this purpose I need to determine the RPM and currently active gear in a manual transmission vehicle. I am working on a Ford Fiesta 1.6 Petrol and reading the information from OBD2 using CAN and I can read the RPM but there is no standard PID for gear. Does anyone know how to determine the currently engaged gear for a MT vehicle from OBD2 at least for Ford Fiesta if not generally.

Also I wanted to know if I can use the engine load value (PID 4, Mode 1) to determine of the engine is going to stall?

  • I don't know about your Fiesta, but mine already has a shift indicator. And it's annoying... Dec 20 '15 at 22:20

You can determine the gear by comparing the engine RPM and the vehicle speed. Most cars that have a shift light though do not actually know what gear they are in, they use engine RPM, engine load and throttle position.

A near stall could be determined by looking at engine load and RPM. Low RPM and high load will give it away.

  • There are several problems with this. 1. Can't determine reverse. 2. Can't determine if the car is in neutral and just rolling (under some circumstances) Dec 21 '15 at 13:03
  • 1
    @MohammedLokhandwala Reverse generally has an input to either the PCM or BCM. If the car is in neutral and rolling then engine RPM and engine load will be low compared to if in gear.
    – vini_i
    Dec 21 '15 at 13:09
  • PCM/BCM information for gear even reverse gear for Ford is what would help. It seems impossible to find any reliable source for the enhanced PID for Ford. Surprisingly the Fiesta does not seem to support the Mode 1 PID 1F for Engine On time, one more problem to figure out. Dec 21 '15 at 19:57
  • @vini_i I know this is a pretty old answer, but do you have an example of how the gear would be calculated? Sep 22 '19 at 13:32
  • @SelaliAdobor Compare the vehicle speed to engine rpm. You need to know the ratios, to begin with. For example, 5mph at 1700rpm is probably 1st gear, 80mph at 3000rpm is probably overdrive, and so on.
    – vini_i
    Sep 23 '19 at 15:23

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.