Ryantzer wrote: ↑Tue Jun 11, 2024 11:39 am
I think the rear O2 sensors are not related to your issue, since all they do is monitor the functionality of the cats and have nothing to do with how the ECU controls the engine. Knock sensors are a common issue on the Q45s so if you're getting that code again it's probably likely they need to be replaced. if you're concerned about the cats being clogged or non-functional try a product called CataClean - I'm a long way from being a fan of the 'fix in a bottle' products as 99% of them are snake oil, but I've used CataClean successfully on two different vehicles that were throwing low-efficiency catalyst codes.
Do you have a copy of the factory service manual for your car? It contains diagnostic procedures for every code you'll ever encounter, and was written by the same people who designed and built your car, so it's an invaluable resource for maintenance and repair info.
I’ve tried every damn bottle of catalytic converters cleaner lol. Probably went thru about 4-5 now over the last couple years.
However like I mentioned in previous post, I don’t think the cat is bad at all. Maybe it is old, but not clogged. I never got any codes for efficiency of catalytic though.
I rewired my oxygen sensors, couple years ago I had them replaced at a shop and the guy completely had them all mixed up (not really his fault since the previous owners must have cut the connectors instead of just buying one with them on). But it was like that for years before I finally decided to just do it myself (and I was charged $127 for that work that wasn’t even done right. But the guy who did it doesn’t work there anymore, another issue with where I live: mechanics come and go)
I have the FSM that I download and can read on here. That’s how I was able to figure out the oxygen sensors wiring colors were off. So for the longest time I had steady 0 volts on one, and 1.28 volts on another. Now I have proper readings of them, and I added a connector from eBay just to get it off hard wiring. The front’s were fine, I had those replaced around the same time, and they had original harnesses.
But like I said, a simply adjustment of the camshaft sensor to get my timing right seems to have been the problem all this time. However I’m still getting codes for knock sensor and heater circuit on rear oxygen sensor. I don’t live in an emissions state anyway so not worried about it.
I replaced a bad knock sensor on my maxima awhile back, it didn’t do anything special for performance but clear the code and maybe a couple extra miles to the gallon. Which isn’t bad but, the work to do it especially on the Q: not worth it. However those are the only 2 check engine codes left. If I got those two out the way, I would be check engine free. But I have 2 other vehicles, trying to chase a check engine light is: tedious, especially when it doesn’t always fix the actual issue.
Now, hopefully on to alignment and paint job lol.