CEL and P1171 code on 2000 S70 - MAF Sensor?

[GDATL]

My 2000 Volvo S70 GLT-SE (106k miles) gave a CEL about 6 weeks ago, but it disappeared in about a week. Used my Actron scanner and code was P1171 (Fuel Trim Upper Limit ). "Freeze data" from scanner showed:

on 4 April 2010 - P1171 @ 2000RPM, load value 14.1%, coolant 186F, short term fuel trim 3.9%, long term fuel trim 23.4%,
short term fuel trim3 -100.6%, long term fuel trim3 100.6%, vehicle speed 45mph, fuel system1 CLSD, fuel system2 N/A.

Since CEL went out, and it was almost time for emissions testing required for registration, I cleared code. All went fine until yesterday when CEL came on again and code was same P1171. Data today was:

on 1 May 2010 - P1171 @ 2360RPM, load value 9.8%, coolant 199F, short term fuel trim 1.5%, long term fuel trim 23.4%,
short term fuel trim3 -100.6%, long term fuel trim3 -100.6%, vehicle speed 65mph, fuel system1 CLSD, fuel system2 N/A.
Catalytic converter and both O2 sensors replaced about a year and 8,000 miles ago. No visible cracks in vacuum hoses, but did not check throroughly, and I don't have a way to check for vacuum leaks. Reading online says probably MAF sensor. Could try cleaning, but since daughter taking car back to college tomorrow, may just replace MAF. Will that most likely fix it? And do I disconnect battery for 15 min to "clear" fuel data table (I read that somewhere a while back). Thanks for your input!

[greencupbay]

A dealer told me that if both trim limits are throwing codes, that means (more than likely) that you need a new MAF; if only one trim is throwing codes, that usually means you need new O2 sensors on that bank/trim. Sounds to me like you just need to start by cleaning your MAF and possibly a new MAF. A simple troubleshooting for the vacuum hoses is to get some ether at the store and spray it around all your hoses (don't blow yourself up). Look and listen for a surge in the engine and that will tell you where it is. That's not always a sure-fire way of knowing though. Get some MAF cleaner first and clean it up to see what it does.

[SilverS70]

I had that same code P1171 on my 2000 GLT-SE also. I cleared the code, cleaned the MAF, and it was back within 2 weeks. Almost left me stranded if I didn't know you could unplug it, and limp home. Replacing the MAF fixed it. If its your daughters car away at school, I'd just replace it. I also put in a new air filter at the same time.

[jblackburn]

I'd replace it - cleaning is a short term solution at best.

Mine up and died in the middle of the interstate without warning.

And do I disconnect battery for 15 min to "clear" fuel data table?
Yep! It'll need to re-learn how to run without strange values in its table.

[GDATL]

Thanks for the replies. It is tough to find a new MAF sensor late on a Saturday afternoon (Voluparts in Atlanta only open M-F, my local repair shop is closed on Saturdays, and I didn't want to call one of the 3 local Volvo dealers (why pay $250 for what I could get for $125 at FCPGroton if I could only wait a few days!) so I checked out good ol' NAPA. I had previously found NAPA to be a good source on weekends for S70 parts (things like brake hoses, brake calipers, etc). Weekends are usually when I work on cars (and when I figure out that there was a part I forgot to order!) They had a rebuilt Bosch MAF Sensor for $119. NAPA says that they were rebuilt by Bosch for NAPA and then repackaged in a NAPA box (I can't verify that).

I disconnected the battery before I removed the old MAF sensor and it was disconnected for about 30 minutes until I finished the replacement. (Easy job for a DIY'er!) As you would expect, the CEL was off and the codes cleared. I'll send my daughter on her way and have her get the emissions test completed after she drives about 100 miles or so. Hopefully that will be enough distance for the sensors to collect enough data to pass the emissions test. And hopefully that was the cause of the P1171 code and CEL will stay off for a long time!

Silver S70 - wish I had seen your post before I went to NAPA! Probably time for an air filter, and I actually removed the air cleaner cover to make it easier to remove the MAF sensor! (Both my 2000 S70 GLT-SE's are also silver - one with 106k and the other with 154k.)