2012 Ford F-150 5.0L - P2196 and P2198 - O2 Sensor Codes
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General Information: A 2012 Ford F-150 came to the shop with a check engine light on. The customer had the truck scanned at a parts store and they told him that he needed O2 sensors. He wanted us to look at it to find out what is wrong.
First Thoughts: Many people make the mistake of putting O2 sensors in these vehicles just because they have a code for it. I have done many of these Fords that say that the O2 sensors are stuck rich but actually have another component that causes them to be stuck rich. Just like with any trouble code, proper diagnostic work needs to be done to determine the root cause.
Diagnostics: The first thing I did to this truck was hooked up a scan tool to it to read the trouble codes. It had:
P2196 - O2 sensor signal biased/stuck rich - bank 1, sensor 1
P2198 - O2 sensor signal biased/stuck rich - bank 2, sensor 1
Frequently Asked Question:
Where do I find wiring diagrams and step-by-step repair procedures for Fords?
The best online resource I use is Alldatadiy.com.
I used it for this case study to find the correct procedure for this 2012 Ford F150.
I have noticed on Ford vehicles that have these codes that it is not always the O2 sensor, but a component from the EVAP system that is causing these codes.
If you look at the live data below, you can see the fuel tank pressure is being pulled into a vacuum. There is only one component in that system to do that.
The EVAP Purge Valve.
The purge valve opens to allow vacuum from the engine to suck fuel vapors from the EVAP canister and fuel tank. If the purge valve is opened all the time and sucking fuel vapors into the engine, this would cause a rich condition, which the O2 sensors would catch.
As you can see from the live data below the purge valve is closed at 0% yet the fuel tank is still going into a vacuum.
In the live data below, the humps in the fuel tank pressure PID are from where I opened up the fuel cap and allowed the negative pressure to go up.
Even in the short term fuel trims, the truck’s computer is trying to correct for the extra fuel by taking away fuel -28.8%.
If the O2 sensors notice a rich mixture in the exhaust, the engine computer will try to correct it by having negative numbers on the fuel trim. A properly working vehicle will have total fuel trims(Short Term + Long Term) ranging from -10 to 10, but ideally 0 is perfect. In the case, -28% is too much correction, which indicates a problem.
What fixed this vehicle?
After replacing the purge valve, the truck didn’t have any codes return. Fixed!
Even the Ford Mustangs are having this issue. Check out this case study I did on a 2015 Ford Mustang with purge valve issues.
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