MR2 Check Engine

Shown here is the 1991 Toyota MR2. Thanks to the mechanical skills of a family enthusiast, it purrs, growls, and turbo whistles like a dream.
 
My hardware ability doesn't go much further than oil changes. Rather, my expertise is in software, and I wrote an Android App (iOS version is in progress) to diagnose the flashes of the check engine light.

This second generation MR2 predates the OBD2 connector, a standard used to diagnose engine, transmission, and emissions problems quickly and easily. Instead, we have a flashing check engine light which needs some deciphering, followed by a lookup in the service manual.

Basically, you count flashes to arrive at fault code number. A short pause (~1.5 seconds) indicates the start of the next digit. A medium pause (~2.5 seconds) indicates start of the next fault code. And a long pause (~4.5 seconds) means the sequence has ended and will repeat.

The video below corresponds to the codes 41 and 51.


Using the the MR2 Check app and selecting the 3S-GTE engine:



we learn that 41 indicates a problem in the throttle position sensor signal, and that 51 indicates a switch condition signal.

There are two ways to enter the codes. The first is to enter them (separated by a space) using the NUM PAD:


The second way is to use the BLINK PAD. Match the blinking pattern by first tapping START, followed by the BLINK button for every flash. You don't need to match the flashes precisely; rather you just need to match the rhythm.  Also, going through two sequences helps improve the accuracy.  Press STOP when you are done with the sequence.



As an Easter egg of sorts, use the NUM PAD and enter 100 to see all the codes for the selected engine.

MR2 piston heads already know that to get the flashing check engine light you need to jump two pins on the diagnostic port in the engine bay.  I've added photos to help new owners:


Diagnostic Port in Engine Bay


Jump pins TE1 and E1

As per Toyota, prior to jumping:
  • Battery voltage needs to be 11V or more
  • Throttle valve full closed (throttle position sensor IDL points closed)
  • Transmission in neutral position
  • Accessories switched OFF
  • Engine at normal operating temperature
Then turn the ignition switch ON, but do not start the engine. Now ready to jump pins.

For the bit heads, this app was written on a Mac, using Android Studio and Kotlin. The iOS version uses Xcode and Swift.

MR2 Check is currently available on Google Play for $1.99.  Think of it as buying me a cup of coffee. Or about a half gallon of gas.




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