JUST Picked Up a 13 XLT with 105k on it. Drives like a dream minus the engine light that pops up on the way home from the used car lot that’s a P0430 code.
Where the Hell are the O2 sensors and should I just do all?
WELCOME TO THE FORUM!
I always recommend replacing them all at once, because if one goes out they are likely to nickel and dime you until you do, usually a week in between...lol.
But if your code calls out a specific one do that one because they aren't that cheap, especially if they are "heated" O2 Sensors.
O2 Sensors are on the exhaust, 4 of them on most vehicles:
Left and right side of the Exhaust, Bank1 and Bank 2. Bank 1 is usually the side of the engine that Cylinder 1 is on, and Bank 2 is the side where Cyl 2 is. (This is not a certainty, just a general rule)
2 of them before the Catalytic Converter (Upstream or "Sensor 1")
2 of them after(Downstream or "Sensor 2").
EXAMPLE: The Code will call them out as "Bank One Sensor 1" or "O2 Sensor B1S1"( Bank 1 Sensor 1). This means that the Upstream O2 sensor (Before the Cat) on Bank 1
All of this can be checked with a code reader that shows "Live Data" in the Global OBDII.
Be sure to look at your data as the car is running:
After a little warm up time, an Upstream O2 sensor should switch from low to high voltage rather quickly, while the Downstream O2 sensor will be slower to react, since it is measuring the exhaust affected by the Cat. Pull up the graphs in the live data and look for the oddball.
This will affect your Short Term Fuel Trim(STFT)and Long Term Fuel Trim(LTFT) numbers as well for Bank 1 and Bank 2, ,that can be another indicator of where the problem actually is. Fuel Trim is a representation of how the computer is metering the fuel to the engine using the opening and closing of the injectors. It can also be affected by vacuum leaks, etc...
STFT is what the engine is doing NOW. This should hover between 5% to -5%, give or take. A spike in either direction isn't necessarily an issue.
LTFT is the average setting that the Computer uses to tell whats happening and if there is a problem. This should be within 7% to -7% on most vehicles, but if it is past 10% to-10% on either bank that is where your issue is. Fuel Trim issues will usually set their own code, but this is another place to look. Fuel Metering is sometimes tricky to troubleshoot.
Another possibility is that your Catalytic Converter IS actually having issues. Again most computers will set a code specific to it, but look for Downstream O2 sensors reading lean, but not stuck at a certain point, and some stalling or other driveability issues.
So before you just go drop a couple Hundred dollars on O2 sensors just to have the problem persist, do your homework.
Good Luck!
