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Well I have an update. My engine is still running great, no misfires or coil failures. However, my transmission has intermittently started to shift strangely for no apparent reason. It sometimes upshifts very early while accelerating, then it downshifts and goes back and forth a few times making the car feel like it’s chugging before it straightens out. Engine runs well. It reminded me a lot of when my TPS went bad.
My first step was to put test lights on the shift solenoid wires to see if the ECU is commanding the shifts or if the trans is doing it on it’s own. I found that the ECU is in fact commanding the odd and erratic shifts, so I checked MAP and TPS signals on my Scangauge while it was acting up and they both looked good.
My next step was to swap my ECU with a known good spare. I have a JDM ECU and several spares, so swapping was easy since it doesn’t have an immobilizer. As soon as I swapped the ECU, the trans started to shift correctly again. I initially thought that the ECU went bad since it shifted correctly after I changed it, but then I remembered that the ECU I installed was older and wouldn’t work with my 05’s wideband o2 sensor, so I accidentally changed 2 variables. I put the other ECU back in, unplugged the o2 sensor, and it now shifts perfectly.
So I am wondering if a bad o2 sensor can cause shifting problems, or if the problem is more likely the ECU. I likely have another wideband JDM D17 ECU in my bin, so if I do I will throw that in and see if it still does the same thing with the o2 sensor plugged in.
Maybe the ECU was damaged by interference over a period of several months? Is that possible? Thanks
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