I have a 99 f150 with the 5.4 triton and my check engine light is giving me a code that says: Lack of HO2S21 switch, sensor indicates lean. I'm wondering if anyone knows what would take care of this issue? thanks!

 

not sure if this helps but it looks like an 02 sensor issue http://www.casc.on.ca/forums/showthread.php?t=16221

 

I had it in with an O2 sensor code and they said it tested fine but maybe this is a different code saying its actually bad i have no idea

 

Need the p-code plz. Pxxxx for example

 

It didnt give me anything like that

 

http://www.obd-codes.com/trouble_codes/ford/p1151.php

found this hopefully one of them is the answer!

 

Check the connections at the o2 sensors. Or replace. But you need to know which bank

 

The discription as given is BANK 2, SENSOR 1 or drivers side upstream (nearest engine).
What's the code? Likely a 174 code.
This is why you don't know what to do with it.
If the reader/scanner only gives you the OX sensor location, get another reader that reads P code numbers.
Then you get the Ford code discription.
After that, you have places to look for the issue that is causing the code to be set. Hint, it says 'lean'. As in air leak at some point in the intake.
Said another way, it likely is not the sensor that is at fault but the only way the system has to tell there is a problem at some 'other point' in the induction system.
It's not as simple as your thinking.
Good luck.

 

You really need to get the p code for us to help you. Could be a bad sensor or it could be a vacuum leak causing the lean condition infact thats probably the case but I could tell for sure if you posted the correct code. Autozone and other parts stores will pull them for free. Get the EXACT p-xxxx code and bring it back to this thread.

 

P1151

 

You need to check for vacuum leaks. is the airfilter good? check the PCV system the rubber elbow tends to rot out at the back of the throttle body then just check for vacuum leaks in general. Thats where you should start..

 

clean your MAF sensor to.

 

Code 1151 is the same as code 174 for the same cause and repair..

 

But, I believe the 1151 you replace the sensor. At least that's the way Ford UK has it. Scorpio.

 

Ok thanks guys! i have a cold air intake thats not very old so i know the filter is good, but i will check my connections and do i have to use anything special to clean the maf sensor so i dont wreck it?