P0171 and trouble pumping gas

4879 Views 17 Replies 2 Participants Last post by csaxon, Apr 16, 2011

lad722

Discussion Starter · Apr 4, 2011

I hope someone can help me with my 2000 Avalon XL. 6 mos ago I lost the vacuum in my gas tank (when I took off the cap, there was no suction sound and pump would cut off every 5-10 seconds when trying to fill). A few weeks ago, my CEL came on. The dealership pulled a P0171 code and told me that the MAF and charcoal canister needed to be replaced (said the latter had a spider's nest in it but there's no code). (Estimate says: MIL DTC P0171 system lean Mass Air Flow Sensor Open.) I looked around on this forum and found info on cleaning the MAF, which I did. I also replaced the air filter (it was quite dirty). The CEL went off (although I did unplug the neg. terminal) and it fixed my gas pumping issue although there is still no suction sound. Unfortunately, the CEL came on during a long drive today with the same code (2 faults). What should be my next step? Replace the MAF? (FYI, I'm a female novice so I can do this, but will likely need a trip to the garage to deal with the canister. I don't have the torque wrench needed.)

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csaxon

· #2 · Apr 4, 2011 (Edited)

Are you saying you can pump gas normally now?
MAF CHECK Notice the air temperature range on the chart when testing. Did you clean the bulb as well as the wires?

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csaxon

· #3 · Apr 4, 2011

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csaxon

· #4 · Apr 4, 2011 (Edited)

Maf bulb

Dirty wires

Clean wires

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csaxon

· #5 · Apr 4, 2011 (Edited)

Also, look for disconnected or cracked air hoses and the air filter housing seal. This isn't yours but it shows where to look.

Looks good but it's not!

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lad722

Discussion Starter · #6 · Apr 4, 2011

whoops! didn't clean the sensor wires!

Thanks so much for your advice, csaxon!

I didn't know about the sensor wires in the MAF so I hadn't cleaned them. I only cleaned the bulb (I watched a YouTube vid on it and that's all the guy did). I'll buy some spray cleaner (for MAFs) although somewhere I read you could put alcohol in a ziplock, put the MAF in for 20 min, then let it dry for a good long while. (I don't have an ohmmeter or voltmeter so I didn't test it.) I'm still flummoxed as to why I could fill my gas tank without the cut offs but still have no suction (not that I'm complaining

) The car has just over 100K mi. I'm betting that I don't have a hose issue since the dealership checked and said nothing about hoses, but I plan on checking them (I'm not really sure what or where the vacuum hoses are that another post on this code mentioned, but I can check the air intake hoses/assembly easily enough. I may try swapping out the air filter since I didn't replace with OEM. And in a few days I'm going to try to get under the car to inspect the canister/hoses.) I'll let you how your advice turns out! Thanks!

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G

· #7 · Apr 4, 2011

lad722 said:
I'm still flummoxed as to why I could fill my gas tank without the cut offs but still have no suction (not that I'm complaining ) The car has just over 100K mi. I'm betting that I don't have a hose issue since the dealership checked and said nothing about hoses, but I plan on checking them (I'm not really sure what or where the vacuum hoses are that another post on this code mentioned, but I can check the air intake hoses/assembly easily enough. I may try swapping out the air filter since I didn't replace with OEM. And in a few days I'm going to try to get under the car to inspect the canister/hoses.) I'll let you how your advice turns out! Thanks!

If you are now pumping gas normally, and there are no current EVAP system codes, I suspect the tech cleaned out the "spider nest" which opened the line. I would leave this alone unless the gas pumping problem returned or you get a CEL and have EVAP system codes. Most of the big auto parts chains (Advance, Autozone, etc) will pull codes and print them out for you for free, so you don't have to go to a dealer. And aftermarket air filters are fine as long as you got the right size/shape.

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csaxon

· #8 · Apr 4, 2011 (Edited)

DO NOT PUT THE MAF IN A BAG OF ALCOHOL!
Get a swab and dip it in the cleaner and gently swab the wires clean. The MAF spray cleaners work follow the instructions.
Leave your canister alone; if the gas pumping problem re-occures just post here again.

http://www.toyotanation.com/forum/t96508.html

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lad722

Discussion Starter · #9 · Apr 5, 2011

Actually, I still had trouble pumping gas after the dealership checked my car out so I don't think they cleared out any nest. I've only pumped gas once since I tried to clean the MAF. FWIW, I bought an OBD2 reader so I won't be going to the dealership for that (they had a coupon online for a free CEL scan, so it actually didn't cost me a penny to have them check).

lad722

Discussion Starter · #10 · Apr 5, 2011

No more alcohol for me!

csaxon said:
DO NOT PUT THE MAF IN A BAG OF ALCOHOL!
Get a swab and dip it in the cleaner and gently swab the wires clean. The MAF spray cleaners work follow the instructions.
Leave your canister alone; if the gas pumping problem re-occures just post here again.

http://www.toyotanation.com/forum/t96508.html

Thanks... don't worry, I'm buying a can of MAF cleaner tomorrow. I'm not messing around with any more q-tips. I don't want to damage the wires by accident.

G

· #11 · Apr 5, 2011

lad722 said:
Actually, I still had trouble pumping gas after the dealership checked my car out so I don't think they cleared out any nest. I've only pumped gas once since I tried to clean the MAF. FWIW, I bought an OBD2 reader so I won't be going to the dealership for that (they had a coupon online for a free CEL scan, so it actually didn't cost me a penny to have them check).

Code readers are great to have. Now, can you read your codes and post them so we know what your current issues are? Even if the MIL light is off, you might have some "pending" codes. Are you still having trouble pumping gas?

lad722

Discussion Starter · #12 · Apr 6, 2011

OK, I pumped gas yesterday and had no problem. Today I used the MAF cleaner. The code reader still shows 2 P0171 codes (no others). I don't know if I should erase them or wait and see if driving resets the computer.

G

· #13 · Apr 6, 2011 (Edited)

lad722 said:
OK, I pumped gas yesterday and had no problem. Today I used the MAF cleaner. The code reader still shows 2 P0171 codes (no others). I don't know if I should erase them or wait and see if driving resets the computer.

You should go ahead and erase them. If they come back, the light will come back on and you will know that you have not yet resolved the problem. If you don't erase them and you haven't reolved the problem, you will have no positive indication that the trouble still exists. Many codes do not automtically turn the MIL light off even if the issue is resolved.

lad722

Discussion Starter · #14 · Apr 6, 2011

Drive cycle?

bobflood said:
You should go ahead and erase them. If they come back, the light will come back on and you will know that you have not yet resolved the problem. If you don't erase them and you haven't reolved the problem, you will have no positive indication that the trouble still exists. Many codes do not automtically turn the MIL light off even if the issue is resolved.

OK. I was a little nervous about doing that since the manual for the reader said this and I have no idea what the last part means: "When DTCs are erased from the vehicle's computer memory, the I/M Readiness Monitor Status program resets status of all the Monitors to a not run 'flashing' condition. [That, I get.] To set all of the Monitors to a DONE status, an OBD 2 Drive Cycle must be performed. [Huh?]"

G

· #15 · Apr 6, 2011

lad722 said:
OK. I was a little nervous about doing that since the manual for the reader said this and I have no idea what the last part means: "When DTCs are erased from the vehicle's computer memory, the I/M Readiness Monitor Status program resets status of all the Monitors to a not run 'flashing' condition. [That, I get.] To set all of the Monitors to a DONE status, an OBD 2 Drive Cycle must be performed. [Huh?]"

What that means is that you can't just erase the codes at an emission test site, and then pass the OBDII emission test that many states use. After you erase the codes, you have to drive the car some before you take it to be tested. This is to prevent people who have emissions problems from erasing the codes after stopping the car in a test site, thus appearing to be in compliance when they are not.

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lad722

Discussion Starter · #16 · Apr 6, 2011

OK. They're erased. I'll be driving at least 50 mi. in the next week, so it shouldn't take too long before the monitors stop flashing. Thanks again!

lad722

Discussion Starter · #17 · Apr 13, 2011

Update: Problem fixed!

lad722 said:
OK. They're erased. I'll be driving at least 50 mi. in the next week, so it shouldn't take too long before the monitors stop flashing. Thanks again!

I just used the code reader to check to see if the EV monitor has reset and it has. I got the green light! Cleaning the MAF fixed all my problems! Thanks for your help!

csaxon

· #18 · Apr 16, 2011

Glad to help. Sorry I haven't been around lately. My computer has been up and down.

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