Indeed. I think the pending part is where the reading has been out of tolerance far or often enough to flag the 'pending' but not hit the threshold to flag the CEL. It says there's an issue but not serious enough to CEL over yet.

 

Pending codes are basically intermittent problems. A pending code is something that failed during one run cycle, but not every cycle. Pending codes are stored for a certain number of run cycles (40 or 50 cycles comes to mind, but may not be accurate) and if they aren't recurring, will be cleared automatically. If it happens often enough, it will move from pending to an actual diagnostic trouble code and can only be cleared by both fixing the problem and clearing the code with a scan tool.

Fun fact for the OP: OBD-II systems have massively improved the accuracy of troubleshooting modern cars. Gone are the days of blasting away with the parts cannon to see what works. Simply pull the code and follow the diagnostic flow chart from the manufacturer. A multimeter is mandatory, and a test light is a solid addition to aid in the diagnostic procedure. If you have opposable thumbs, and can read words and look at pictures, and correlate the two with what's physically sitting in front of you in your garage, you can troubleshoot most any electrical issue.

 

I agree. Was as bit stymied by the two sensor fails on basic sensor technology. I am an Electrician by trade btw so troubleshooting electrical issues is common place for me. That being said sometimes extra thoughts and experiences are helpful. For that I thank everyone who chimed in.

 

You COULD be right, Mandrake. But as i said mine seems to have taken a while to settle down. Still may have issues, but will keep on digging if i do, till it gets resolved, or it kills me, just a stubborn, old, cantankerous S O B, that's me in spades.

 

Agreed Wingrider.......like the line in Dirty Harry says "" I gotsta know""

 

Wing, without knowing the details of your situation, I can only speculate, but if it took a while to settle down as you say, then that was a pending code, not a hard DTC, and you didn't bother going in to clear any codes when you replaced the sensor. Pending codes, as I mentioned previously, will clear themselves if the issues doesn't return after a certain number of run cycles. That's not learning. That's the sensor sending the proper signals back to the ECM. Sensors aren't like a new pair of shoes where they take time to break in and your feet get used to them. When you plug a new mouse or keyboard into your PC does it take a while to learn the new keyboard, or does it work right away? EFI is no different.

Don't believe me? Stop by your local dealer and ask the shop foreman if the ECM has to get used to new sensors.

 

Have a separate thread already for this issue, Mandrake. The PO101 code is one of the worst to track down sometimes!! More than one shop has said the very same thing, could be ANYWHERE, a real pain in the back side to find sometimes!!! My question is, Is this normal after installing a new M A F sensor, that's been throwing this code for over 6,000 miles? It seems to be going backwards from the way it occurs.

 

If you're still having issues, could you link me to your thread, please? That way we don't hijack this one, and the discussion stays out there for the next guy.

 

When using forum/web Search, PO101 is actually P0101 (and it matters). (i.e. zero, not oh - though people often say oh)

 

Mandrake title is;

PO101 code keeps popping up

This problem is of a similar issue to mine, just an attempt to be helpful.

 

Well its been over 5 weeks since I took out one MAFS and gave it a right thorough cleaning. Nothing has popped up code wise and that is that.
Felt an update was needed for those who were in on this thread.
Saved $300 btw. Thanks for all the help.

 

Have you driven the car hard since cleaning the MAFs? I get this code from time to time, even after cleaning my own MAFs a few weeks ago but I've noticed it only seems to come up when the car is driven hard. I've resigned myself to getting some new ones, looking to find the correct Denso equivalent for mine.

 

I have pinned it with no ill effects

 

Good stuff, glad it worked out for you.