The wife's Monte just threw P0171 again. Crap... The MAF sensor cleaning must not have been enough, or maybe wasn't the problem at all. Guess I'll be swapping out O2 sensors sooner rather than later. And with our trip to MI coming up Saturday morning, looks like I'll have to buy sensors locally rather than getting the good Amazon deal.

 

Find a way to get a free prime membership account and you can get free 2-day shipping on everything or $3.99 overnight shipping.

This O2 sensor also messes with your MPGs, so doing it before a road trip is very beneficial.

 

Yeah, that's why I figured I better take care of it immediately. Plus I don't want the 'Check Engine' idiot light lit-up the whole trip.

 

Got up early this morning to install the new O2 sensors. Quickly discovered the O2 sensor socket I was sold yesterday doesn't fit! Grrrrr... Back to the auto parts store before work. Got a new one; made sure it fit before leaving the store. If the engine is cool enough, I'll try the remove / replace this evening after work. If not, up early again tomorrow morning.

 

I thought you grabbed the same one as me?

 

No, I ended up buying locally (at a higher price...) due to the time crunch. I didn't want to risk getting it too late from Amazon to get the work done prior to our early Sat. morning departure. I went with Bosch sensors as they were readily available at my favorite local parts store (an O'Reilly nearby - no affiliation just a happy customer), have a lifetime warranty, and the shop is really good about honoring the warranty on anything they sell. I've come back with parts I fried through operator headspace (i.e. I screwed up) and they said "no problem" and promptly exchanged for a new part. Did that recently with an ignition module for my old car that I fried due to outright stupidity.

The O2 sensor socket I bought should have fit the Bosch sensors in theory. The head was the right size (7/8"). But I think the sensor body was a little bigger in diameter. The sensor body was getting hung-up and preventing the socket from reaching down to the head. Weird. The new one looks odd, socket wrench fitting is offset from center, but it fits (see center / right of attached pic). Probably not as effective for leverage, but better than my open ended wrenches given the tight quarters.

 

OOO I see. Yeah I saw those too, but didn't know the type of abuse they could take lol

 

I got both O2 sensors swapped out last night. Once I had the right socket, it was a piece of cake. The offset socket I used isn't the ideal solution, it requires more room to maneuver, repositioning of the socket if many turns of the wrench are needed. But luckily as soon as I got them started, both sensors easily came out the rest of the way by hand. The toughest part was getting the cable ties loose to disconnect the old sensors. And trying to work some slack in the downstream sensor cable. The connector was very well hidden inside a heat shield. Couldn't get it unplugged until I worked at least a couple inches of slack in the line.

P0171 code is cleared - again. I'm hoping it's gone for good this time. Or at least for many, many thousands of miles.

Thanks for the help earlier, Mike.

 

Glad I could help and you got everything done!

I hope that stupid code stays gone, and you get good MPGs for your trip

 

So I'm learning to hate the P0171 code. From what I've read, so do a lot of other people.

After replacing both O2 sensors, the code went away... for a day. Just as we were heading out of town on vacation, the 'Check Engine' light came back on. I didn't have time to verify that is was still the same code but that seems most likely. Since I already cleaned the MAF sensor and replaced O2 sensors, I started looking for a vacuum leak (squirting electrical contact cleaner around the intake / connectors / sensors to see if it would trigger a change in idle speed). I recently had both upper & lower intake manifolds off; entirely possible that I inadvertently caused a vacuum leak with a hose or sensor somewhere. Couldn't find any leak.

The Check Engine light stayed during almost the entire trip. It just went away two days ago. Hasn't reappeared yet. The only thing I did during our trip was to put in a can of SeaFoam, then a milder gas treatment with every fill-up. Waiting to see if the code pops again.

I'll post an update if/when the saga continues...