2007 Acura MDX 237,xxx km
i guess I’ll start from the beginning

got the car for cheap just bc of O2 sensor and j pipe needing replacement, bad O2 would cause SH-AWD light and CEL light to come on and disable AWD. After replacement of O2 problem went away. The cats were old and worn, I knew this from the low efficiency code on bank 2, eventually they blew through clogging up my third cat completely, we replaced third cat, leaving the blown bank 1 & 2 cats since I couldn’t care less. Obviously I had a constant CEL for emissions since both cats had low efficiency codes. Car runs and drove fine for 6+ Months. Recently I noticed a leak from oil filter housing, since I did the same gasket on my tl I kinda assumed it’d be the cause of the leak, the day before doing the gasket replacement I drained old oil, filled in some cheap 5w20 synthetic and some risolone oil additive, took it for a quick drive. Then next day drained the oil, and it was super black, additive seemed to work great, I proceeded to change out the gasket, add a new Castrol filter, and castrol synthetic 5w20.

car drove fine all day, no leak. Then as I was driving I overtook a truck, then was greeted with a check SH-AWD and a check VSA system light, with all the lights on the dash illuminated (SH-AWD, VSA, triangle with exclamation mark) and full limp mode with rev limiter stopping at 5000ish rpm. Even after turning off and on problem presists, instantly I checked the OBDII codes, still only the two low cat efficiency codes. Is it just because my reader isn’t good enough to read VSA module? I saw one person online say it was due to oil pressure switch / vtec solenoid. I did just change the hosing where those are both located but I didn’t unplug the connectors, I left them plugged in and just hung it with a bungee cord, maybe I still somehow pulled one of the wires, still doesn’t explain why it drove fine for hours before.

any ideas where I should start to look?
im thinking maybe wheel speed sensors or the vtec solenoid and/or oil pressure switch

 

So my guess was right, plugged back in the scanner today, 3 P2647 codes appeared. Vtec oil pressure circuit, rocker arm actuator, bank one stuck on

 

There's a service bulletin for the pressure switch and a software update to go along with it.

 

okay so the day before this happened I changed out the oil filter housing gasket, along with an oil flush. Maybe something got jammed in there. I had a spare housing and solenoid. I thought it was the solenoid itsel so I took it off to switch them, when I removed I noticed the spring loaded actuator was in fact stuck pressed down, like completely stuck, swapped in my spare housing and re used solenoid just added a new gasket. And problem solved, I’m used to my sh-awd turning off when a code is thrown like when I needed a upstream o2 sensor, but I had never experienced full limp mode with no VSA and capped at 4500rpm.

either way it was a super easy fix and took less then an hour if you have the parts. You can replace the spring actuator itself but mine was stuck and I had the spare housing anyway so I just replaced the whole thing.

I hope this helps anyone having similar issues, it can be nerve racking seeing the Christmas tree of lights on the dash, but that’s just the car trying to protect itself from further damage.