2010 Impreza R - APP Sensor and TPS showing strange values via OBD2

May 26, 2023
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Hello everyone, this is my first post here :)

I recently bought a 2010 Impreza R (2.0 automatic) and I've been facing some strange accelerator behavior sometimes. There's a point in the accelerator pedal were it seems the car doesn't know what to do (engine seems to lose power for a short period and go back to normal again).
So, I bought a cheap OBD2 sensor and connected it to my phone to read the diagnostics of my car. No error codes were found but, the Accelerator Pedal Position Sensor never reached 50%, even when flooring it. And the TPS, when flooring, was showing 67% only. Is this correct? shouldn't it be 0~100% in both APP and TPS? Is there a way to test it with a multimeter?
BTW, the car was bought in Brazil (were I live)... I don't know if is there any difference related to that, but there you have it :)
Thanks in advance.
Pick a model and engine.


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Pick a model and engine.
None of those, unfortunately :(
Mine is a 2.0 (the engine is an EJ204) with automatic gearbox (4EAT)... it was not sold in USA market I believe. Maybe it shares the same parts with the WRX or the 2.5 GT but I'm not sure.
You have the incorrect scan tool to look at this model. Read this entry below. The examples, I use with a factory scan tool.
Free SSM 1.2.5 is PC based and working on older Subaru models without CAN, only K-Line.
Works with XP, Windows 7 and Windows 10. The application will access SSM full Engine and Transmission diagnostics.
Link: https://sourceforge.net/projects/freessm.berlios/files/latest/download
USB Cables used:
VAG-K + CAN USB (at times called KKL or K plus CAN)
Examples of operation:

Android Tools used:
JDMscan Application: https://play.google.com/store/apps/details?id=dksoft.jdmscan&gl=US
USB Cables used:
OR (FTDI) FT232BL USB with OTG cable if Android supported

ActiveOBD Application Android
Bluetooth OBDLink MX +

ActiveOBD Application iOS version
Requires high quality BlueTooth device such as Bluetooth OBDLink MX +

These tools mentioned are NOT OBD II, these applications are true SSM (Subaru Select Monitor)

I use these tools on these older generation vehicles because they are quick and easy.
With the PC or Android, the screen can be recorded for playback / reference. ie: PC > Camtasia and Android > AZ Recorder

I do this as a Professional Technician and having the latest Snap-On with SSM3 / SSM4 professional tools, they are not cheap.

The USB connections have a much faster refresh rate than BlueTooth but all work perfect for these older models.

Use what suites but these work.
The throttle pedal is a "two signal" potentiometer and each signal should "follow" each other.
View the example "Accelerator signal.jpg".

JDMscan will also graph.
The throttle body is controlled via Engine controller. The electronic motor will open or close via throttle pedal. At the same time, a feed back signal will be produced in ether voltage or percent from the throttle body, returning to the Engine controller.
Another example:
With any decent scan tool, the voltage or percent can be measured on the pedal or throttle body.
Potentiometers can not be repaired.

Not knowing the wiring (numbers and colors) on that model, this may help.


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01-Throttle Opening Angle (%)
02-Accelerator Pedal Travel (%)
03-Combination Throttle Pedal Travel (%) Throttle Opening Angle (%)
04-Live Data choices X6 test 1
05-Combination Sub-Throttle Sensor Voltage (V) Main-Throttle Sensor Voltage(V) (Slow-Held)
06-Combination Sub-Throttle Sensor Voltage (V) Main-Throttle Sensor Voltage(V) (Fast)
07-Combination Sub-Throttle Sensor Voltage (V) Main-Throttle Sensor Voltage(V) (Fast-Held)
08-Live Data choices X6 test 2

Key ON, Engine OFF (KOEO) test applying throttle.


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Ok, so, I'll try to first use the ActiveOBD iOS app you suggested and if that doesn't work, I'll try to get a proper tool to check this (I'm currently using a USCAN OBDII PRO, which I believe is made up here in Brazil). But if the accel pedal is using two pots, I think I can also test them using a multimeter... I would just need to know what values should I find in the correct pins. But thanks for the help here, I'm really interested in how everything works in my car and those schematics are really helpful, thanks for sharing it.
Read the earlier post again. JDMscan was used to capture the graphs with an Android.
JDMscan can also be used with an emulator via PC.
ActiveOBD can graph and should be able to use the identical protocol.
A meter is fine, the oscilloscope is much more accurate.

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