Did previous owners tune ECU?

 

UPDATE: It was either the APS or TPS.

So, after the mechanic guilt tripped me about my mods, I took it to another shop that does tunes to make sure the PCV was working properly. This new tech essentially said the PCV is fine, I have the correct map, etc. He came to the same conclusion as many on this board have, that the issue is likely with the APS or TPS. Just to be sure, I found a used SAI valve and undid the block off the previous owner did. This had a minor affect on this issue. I went back to the original shop (I have to go there since they're the only ones in the area with the Yamaha tool for calibrating the sensors) and had them replace both sensors, despite their lead tech basically saying I was wasting my money. I politely asked them to just do the repair anyway.

Well, after months of getting the run around, wasting money on troubleshooting at another shop, waiting on parts, etc. My XSR900 is finally running like it should. Feels better than when I bought it. Turns out that tech was just being a jerk, and for once the internet was right.

 

What exactly does the APS do? Is it the sensor for the throttle grip position? (sorry for the amateur question)

My '16 suffers from the exact same problem and my tech is providing the exact same advice.

 

What exactly does the APS do? Is it the sensor for the throttle grip position?

Yes.

 

Think of it as a 'fly-by-wire' control system.
The APS is the input you're asking the ECM to move the throttle, and the TPS is the feedback the ECM uses to see what the throttle butterflies are actually doing.

 

thanks for clearing that up 😅

the one thing about the XSR900 vs the FZ/MT09 that is kind of a problem, is that as far as I know, there's no way to calibrate those sensors since the XSR900 doesn't have a diag mode. So, an authorized dealer has to do the calibration, which is why I took it to a shop.

 

Yeah the first gen FZ's were great for that, the diagnostics were in the instrument panel and you could do basically anything you ever need to do without taking it to a dealer.
Starting with the Euro4 bikes (basically 2016 and up), that's been removed.

I imagine you can probe the APS/TPS connectors and measure the sensor voltages to get baselines, then when you install the replacement sensor, try to get the voltages as close to the baseline as possible and it should be good. Assuming the original sensor was giving valid readings at the measurement points (full closed and full open), lol