V-6 Check Engine P0171 & P0420 trouble codes

[mustang67408]

Originally Posted by bayou39

i have a tundra with the v8
is it the same checks?
thanks

Sorry thought ya had a V-6, this was a V-6 forum
Here is the PDF for a V-8
You have a K&N? just curious. How many miles on truck?
I have been noticing poor running/fuel mileage/hesitation/sometimes even misfires, when the Catalytic convereters start to deteriorate and plug up.
HMMMMMMMM Havent had a V-8 with a p0171 in a while. If the MAF specs out ok,find a friend who has a tundra v-8 and swap MAF sensors, just to be sure. Even tho they show good and spec out ok, they can be bad. The person who read your code didnt happen to mention the LONG TERM FUEL TRIM?
fuel pressure is where i'd be looking next. (see attachments)
Then to a plugged exhaust. <--- drop exh and drive, easy test.
Good Luck
-V-

[bayou39]

well i checked the maf sensor i am getting 2.02 resistance at 68 degrees and it should be higher. I also checked the continuity on the fuel pump relay and terminals 1 and 2 have no continuity. Yes i do have the k&n, its been on for 2 years or so and has been fine. The only other thing i did was change the spark plugs to denso iridium ik20's. I am going to change the fuel filter and throw in some fuel injector cleaner this week. This morning i went to drive it and couldnt even get going it was bogging so much. I also hear pinging or something under the hood at the same time. But once I get going it is fine.
My dad scanned the truck for me, so I can rescan at any time to check anything else out. What do i need to find out about the fuel trim? I have 82,000 miles. Thanks for helping me out.

Originally Posted by mustang67408

Sorry thought ya had a V-6, this was a V-6 forum
Here is the PDF for a V-8
You have a K&N? just curious. How many miles on truck?
I have been noticing poor running/fuel mileage/hesitation/sometimes even misfires, when the Catalytic convereters start to deteriorate and plug up.
HMMMMMMMM Havent had a V-8 with a p0171 in a while. If the MAF specs out ok,find a friend who has a tundra v-8 and swap MAF sensors, just to be sure. Even tho they show good and spec out ok, they can be bad. The person who read your code didnt happen to mention the LONG TERM FUEL TRIM?
fuel pressure is where i'd be looking next. (see attachments)
Then to a plugged exhaust. <--- drop exh and drive, easy test.
Good Luck
-V-

[mustang67408]

Originally Posted by bayou39

well i checked the maf sensor i am getting 2.02 resistance at 68 degrees and it should be higher. I also checked the continuity on the fuel pump relay and terminals 1 and 2 have no continuity. Yes i do have the k&n, its been on for 2 years or so and has been fine. The only other thing i did was change the spark plugs to denso iridium ik20's. I am going to change the fuel filter and throw in some fuel injector cleaner this week. This morning i went to drive it and couldnt even get going it was bogging so much. I also hear pinging or something under the hood at the same time. But once I get going it is fine.
My dad scanned the truck for me, so I can rescan at any time to check anything else out. What do i need to find out about the fuel trim? I have 82,000 miles. Thanks for helping me out.

IK20's are for a V-6, You hould be running IK22's.
I Have had bad luck with Aftermarket A/F's. I really do believe in them , I have 1 on my mustang K&N. I just dont think they work well on Toyotas, but since it has been on there a while its probably not a problem.(Thats a whole nother discussion).
The scan tool I use has fuel trim as part of the DATA LIST. Some scan tools have it some dont. Usually the cheaper models that are just code readers dont.
That MAF spec really isnt to far off. "THA" is the air temp sensor portion of the MAF. Other than that swapping out a known good unit is the only other way to be sure it isnt faulty.
Have you tried unhooking the exhaust? 2 weeks ago i had a v-8 tundra that was throwing 4 missfire codes,p0302/p0302/p0306/p0308 and a p0171.
It turned out to be plugged exhaust, The backpressure on that side of the engine was causing so much pressure it wouldnt let combustion happen on those 4 cylinders. Dropping the exh is a lot cheaper than buy a new MAF.
When did this all start?
-V-

[bayou39]

po171 says system too lean on bank 1
which side is bank one? so i know which side of the exhaust to disconnect.
should i disconnect it right after the headers? I am going to scan it tomorrow night again and see what the long term fuel trim is. I originally scanned it like
a month ago or so because the check engine light came on. I finally decided to look up the code the other day to see what i can do with it. Is it a bad thing that i am running ik20's? Thanks

Originally Posted by mustang67408

IK20's are for a V-6, You hould be running IK22's.
I Have had bad luck with Aftermarket A/F's. I really do believe in them , I have 1 on my mustang K&N. I just dont think they work well on Toyotas, but since it has been on there a while its probably not a problem.(Thats a whole nother discussion).
The scan tool I use has fuel trim as part of the DATA LIST. Some scan tools have it some dont. Usually the cheaper models that are just code readers dont.
That MAF spec really isnt to far off. "THA" is the air temp sensor portion of the MAF. Other than that swapping out a known good unit is the only other way to be sure it isnt faulty.
Have you tried unhooking the exhaust? 2 weeks ago i had a v-8 tundra that was throwing 4 missfire codes,p0302/p0302/p0306/p0308 and a p0171.
It turned out to be plugged exhaust, The backpressure on that side of the engine was causing so much pressure it wouldnt let combustion happen on those 4 cylinders. Dropping the exh is a lot cheaper than buy a new MAF.
When did this all start?
-V-

[mustang67408]

Originally Posted by bayou39

po171 says system too lean on bank 1
which side is bank one? so i know which side of the exhaust to disconnect.
should i disconnect it right after the headers? I am going to scan it tomorrow night again and see what the long term fuel trim is. I originally scanned it like
a month ago or so because the check engine light came on. I finally decided to look up the code the other day to see what i can do with it. Is it a bad thing that i am running ik20's? Thanks

Bank 1 is the drivers side of the engine. Yes disconnect it right where the header meets the exh pipe. 3 bolts.
IK20's wont hurt anything, just not the right heat range... so i was told.
I dont think they hurt anything.
When you re scan it see if it tells you:
1: long term fuel
2: timing degrees
3: 02 sensor voltages for all 4 sensors
Just another idea, we just had a 2005 4runner come into the shop that wouldnt run very well. It turned out to be SUGAR in the fuel. Check your fuel fill pipe and make sure it want contaminated somehow.
How much fuel is in the vehicle?
Did you accidentally fill it with diesel? or was there diesel in the GAS pump.
I have seen that a thousand times if i have seen it 1.
Just trying to rule out things.
Diag is very hard over the internet, to bad your not closer
-V-

[bayou39]

This is not a good week for me. I blew my rear differential this afternoon.
Ive been hearing a few clunk noises for a week or so, more when i go around turns. Today I put the truck in drive and heard a bunch of grinding and then it didnt go anywhere. The driveshaft was just spinning. I am 8 months out of warranty as well. So, i didnt get to do anything with it today. The gas tank is full by the way. In the past month I have let it go down till the gas light comes on a few times. I dont think anyone messed with the gas tank. I will let you know the other stuff when i get my truck back. Thanks alot

Originally Posted by mustang67408

Bank 1 is the drivers side of the engine. Yes disconnect it right where the header meets the exh pipe. 3 bolts.
IK20's wont hurt anything, just not the right heat range... so i was told.
I dont think they hurt anything.
When you re scan it see if it tells you:
1: long term fuel
2: timing degrees
3: 02 sensor voltages for all 4 sensors
Just another idea, we just had a 2005 4runner come into the shop that wouldnt run very well. It turned out to be SUGAR in the fuel. Check your fuel fill pipe and make sure it want contaminated somehow.
How much fuel is in the vehicle?
Did you accidentally fill it with diesel? or was there diesel in the GAS pump.
I have seen that a thousand times if i have seen it 1.
Just trying to rule out things.
Diag is very hard over the internet, to bad your not closer
-V-

[mustang67408]

Sorry to hear about your diff. Hang in there things will work out.
Let me know when your ready and we can continue.
Good Luck
-V-

[bayou39]

Finally got my truck back yesterday from having the rear rebuilt. The mechanic was having problems trying to get the pinion bearings. Well I just changed the MAF sensor. The truck idled bad at first after i reconnected the battery and then it cleared right up and runs great. but today the check engine light came back on again. I will have to scan it again to see if its still the po171, Im sure it is.

Originally Posted by mustang67408

Sorry to hear about your diff. Hang in there things will work out.
Let me know when your ready and we can continue.
Good Luck
-V-

[Market525]

After doing some searching & reading this thread, I thought I'd comment on my recent experience. Vehicle - 2000 Tundra 4x4, 3.4 w/ automatic trans. 65,000 miles, and for some odd reason, CA emissions, even though I live in Maine & bought the truck new in New Hampshire.

Anyway, at 64,264 miles, the CEL came on. A quick scan showed code PO172. Since I had an extended warranty, I took it to my local dealer. They replaced the front 02 sensor, and charged the $313.00 bill to extended warranty. The only change I noticed is that my slight pinging was now gone. In the past 3-4 months, the truck had developed a slight spark knock on light load acceleration. The 02 sensor took care of that problem, so I'm guessing the knock was caused by incorrect fuel mixture?

A few weeks later, at 65,045 miles, the CEL illuminates again. I checked the code, and this time it is PO420 - Cat efficiency below threshhold bank 1. Upon returning to the dealer, they said the cat was bad & ordered the part. Back in 2 days to get the repair done, and I was a bit surprised to see what they'd done: replaced the cat, and BOTH front and rear 02 sensors, but this time under Toyota warranty - not under my extended warranty. And remember, my front 02 was less than 1,000 miles old. The service ticket did not list prices, but I did a quick check and just the two sensors & cat list for over $1,200! Not to mention labor, and assorted gaskets, studs, and bolts.

What's the deal here - did Toyota have some type of cat problem that they extended the warranty on? If so, I missed that. Just very surprised to have this type of problem at such a low mileage. Anybody else experience anything like this?
Thanks, Steve

[mcdonnell]

Guys,
I have a 99 4runner that gives two codes for PO171. I have chenged the MAF and the O2 sensor in front of the CAT. will do the fuel filter next. Any thoughts?

Also, I cannot get the key to return to the locked position and therfore cannot remove it. Anyone seen that before?

[mcdonnell]

Guys,
I have a 99 4runner that gives two codes for PO171. I have chenged the MAF and the O2 sensor in front of the CAT. will do the fuel filter next. Any thoughts?

Also, I cannot get the key to return to the locked position and therfore cannot remove it. Anyone seen that before?[/quote]

[humbil]

Hi All

I have a 2000 Tundra V6, had a tune up done and after about a month heard a slight ping at low RPM, now the check engine light came on, took it to a shop they said its running lean, took some advise from you pages and cleaned up the MAF still the check engine light , could it be O2 sensor, or the spark plugs that were put in not the right kind or the air filter that was changed is causing the problem, please help.

[5 Speed]

The V-6 takes a special twin electrode plug, make sure you got those installed. They look just like a normal plug but with two electrodes (not the center of the plug but where the spark grounds there are two). Do you have a scan tool? Did your CEL go out? I had to replace my first O2 sensor pre cat which is actually an air/fuel sensor (on Calif trucks and it looks like you are from CA) and that took care of my problem. When it was going bad I did experience a low rpm ping a few times. Besides that time the V-6 has never pinged. If you like gadgets get a ScanGauge, you can see real time mpg and all the other fun stuff plus see engine codes and reset CEL on the fly. The V-6 has two O2 sensors and are the easy type to replace, the two nuts over studs, not the V8 type that thread into the headder. The only difficult thing about changing them is getting the plastic plug off the harness to let go

[nHedberg]

I have a P0171 CEL. I tried cleaning the MAF and then replaced the MAF still have P0171 CEL. I pulled the EFI fuse to reset... light went out and then came back.

Also, the CEL went out on its own for a day and then came back.

Stock 99 4Runner, Auto, TRD Supercharger.

Can anyone help me out? Suggestions? Thanks!!!