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2006 Ford Escape Hybrid P0171


Topic starter

Is anyone able to decipher what im supposed to be looking for in this live data I got from my car? Trying to fix the P0171 code, but it turns out to be really hard to diagnose.

Here is a link to the live data I recorded:

OBD2 reader live data

5 Answers

I can’t remember if this was the code. It was a long time ago on my Prius. I got a code, and it pointed to the throttle body and MAF sensor. I cleaned the throttle body and MAF sensor, and the code went away. 

P0171 could be related to the MAF sensor. 

A while back i grabbed a maf from the junkyard and it didn't do anything, so I don't think its the maf. I could try to see about a vacuum leak tho, cause I have a pressure hose I grabbed from the junk yard and a pcv valve I got from advanced Auto parts. I don't have a spare MAP sensor, but I could see if I can get one somewhere. Lastly, I also have from the junkyard a fuel filter and 4 fuel injectors. Though these might not be the issue.


clean the MAP, MAF, throttle and check for vacuum leaks.

Also was it actually 43 degrees outside? is the ambient temp reading correctly?

These "too lean" codes are quite common on Fords.



The freeze frame shows that the code was set before the engine reached operating temp (149°F) and the fuel system was in Closed Loop.

The engine was running for around 8 minutes before the code was set.

It was cool outside. Ambient air temp was 43°F and the IAT sensor was reporting 54°F under the hood.

The idle was around 1120 rpms. That seems a little high.

On that 2.3L the desired FP (fuel pressure) during startup is around 39 psi and your FP sensor is reading 40.3 psi @ 1120 rpms so it doesn't look like a fuel delivery problem.

The MAF sensor was reporting 0.67lb/min (around 5g/s) @1120 rpms. That seems high for a 2.3L engine. (but you'd expect that to have the opposite effect, however, you're just looking at a snapshot)

Lastly, the LTFT was at +28.1% and the STFT was at -3.9%.

So it looks like the -STFT might have been starting to pull the +LTFT down but you can't tell from the Freeze Frame snapshot.

You may want to see if there's a relationship between that high +LTFT and engine temp and rpms.

You'd see that in Live Data (datastream) by first observing both fuel trims at startup (after it goes into CL) all the way up to full operating temp.

If you're dealing with an intake manifold gasket leak, as the engine heats up, the metal parts expand and typically an intake manifold gasket leak will get smaller.

If you see the +LTFT coming down after you just let it sit there idling and reaching operating temp after several minutes you may start to suspect a possible intake manifold gasket leak.


Then, after it reaches operating temp,  you could hold the rpms at around 2500 for a couple of minutes and observe both fuel trims over that time period to see if there's still a negative STFT and if it starts pulling down the positive LTFT to something more reasonable. (this takes a little bit so be patient) 

During this you'll want to keep an eye on that FP psi to make sure it's keeping up.

If that happens, then you can be reasonably sure that it's a vacuum leak (but keep reading until the end for the curveball). Combine your findings. Did just letting it idle past full operating temp have any effect on bringing down the +LTFT and if so did holding higher rpms bring the +LTFT down even more? (maybe an intake manifold gasket leak)

Of did just letting it idle past full operating temp have no effect on the +LTFT but holding the rpms high did have an effect? (maybe a different vacuum leak).

Either way, first check the easy stuff. PCV valve and its hose and other vacuum hoses for example.

If that stuff is ok and you're seeing the positive LTFT decreasing at full operating temp during idle OR when you hold it at higher rpms then you may want to start troubleshooting a possible vacuum leak.

Choose your method. Do you want to smoke test it or if you can access the area around the intake manifold you may want to just spray some starting fluid around the area and either listen for the engine rpms to increase or watch the engine rpms in Live Data (also the STFT) to see a more subtle rpm increase which you may not be able hear (and if a higher negative STFT) results.

Then spray around the vacuum hoses and their connections looking for the same thing.

Some more information which you may find useful. @kaizen made a good point with his experience in this. This could be a dirty MAF or throttle body issue.

This data is from a 2009 Ford 2.0L. It's a little 4 cylinder Ford and close to your engine displacement. 

This 1st graphic shows the steady linear rise that the MAF should report (g/s) as the rpms steadily increase. You can see that the MAF isn't seeing 5g/s until 1750 rpms. You're seeing that at 1120 rpms. Your engine breathes harder because it's a little bigger but something to keep in the back of your mind.

You're able to graph the MAF airflow with your Innova 3040rs scanner. You may want to switch the settings to display metric for this instead of US so you can see g/s instead of lb/min for comparison sake.

A dirty MAF will do something like this

Another thing you can look at is the comparison when graphing the TPS and the MAF sensor at a steady RPM increase.

They should graph parallel to each other like this.

With the lean code you're either dealing with a fuel delivery issue, a sensor issue, or "unmetered" air getting into the intake downstream of the MAF sensor, right?

Well, no. ((curveball)) You could have an exhaust/exhaust manifold leak that the upstream O2 sensor is picking up so don't forget to consider that.








I will get another video soon that i hope shows live data, as well as try to change the units of measurement and show a graph. I hope I'm able to fix this issue with the parts I have as recently I noticed that the engine after running for a few minutes doesn't switch to the electric motors when I come to stop lights or going really slow. Nothing is wrong with the battery or electric motors as when I accelerate and brake, the ev gauge still goes up and down. Then if my knowledge is right, the engine itself has to drop to a low enough rpm to turn off and engage the electric motors. Which I believe brings it back to the P0171 code of the engine running too lean.


Search the forum and I'm sure you'll find your answer