Throwing codes p1135 and p0171

My 2001 Toyota Tacoma is throwing the codes p1135 and p0171 I'm thinking its the maf not sure can anyone help...one of the codes sys air fuel sensor the other says it is running lean

 

P0171 is a "System too Lean Bank 1" code. I had an issue with that code for awhile a couple months back. It's usually due to either a dirty/bad MAF sensor or a vacuum leak somewhere. Mine turned out to be a vacuum leak (port on the back of my supercharger came uncapped). Check all of your hoses and make sure they're connected and secured, and don't have any tears in them. Then buy some MAF sensor cleaner (make sure it is for the MAF sensor specifically) and give that a cleaning, it's super easy to do.

Afterwards, disconnect your battery to reset the code and drive around for a few days to see if it comes back. After disconnecting the battery it usually takes a few hours of driving before the code will come back (if it does at all).

P0171 can also be due to a bad o2 or air fuel sensor, which could be the case here since your'e also getting that code as well. I had mine all replaced when I got the code, but it wasn't until we fixed the vacuum leak that it went away.

 

I already cleaned my maf with maf sensor cleaner

 

where would I check for a vacuum leak would that be in the intake sytem

 

They can be hard to detect sometimes, even a tiny leak can set off a code. Basically any rubber tubing in the engine bay you'll want to look over, make sure they all connect to wherever they're supposed to, feel along the hoses to see if you feel any suction or air being pushed in or out of a crack or small hole. I've heard that if you get the hoses a little wet with a touch of soapy water it can help pinpoint leaks, but I've never tried that personally.

Honestly if you're getting another code that relates to the air/fuel sensor specifically then I'd focus on that as being the main culprit, when I got my code they told me they were going to have to replace that sensor to narrow down the issue.

I'm not sure if that's a DIY job (replacing the air/fuel sensor) or if it would be better left to a shop to do...maybe someone else here has experience with that. I'd recommend using an OEM replacement for it though, I've heard nothing but bad things about people using cheaper aftermarket sensors.

 

I should have a new maf by Friday I'll keep you posted thanks for the help

 

No worries, let us know how it turns out. The "good" thing about this code is that at least the truck is still drivable, however you want to take it easy because driving around with a lean fuel system can cause damage long term. Just don't floor it and give it light throttle until it gets resolved.

 

@tcBob

Posted in trip reports with "help" as title.

Made me think someone needed help on a trail for breakdown or similar.

Can you edit thread title and move it to the proper subforum to prevent actual call for help threads from being missed or ignored?

 

My 2001 2.7L is throwing out P0171, P1130 & P1135. I pulled the MAF and it looked brand new, but sprayed it down with some CRC MAF Sensor cleaner anyhow. Checked intake hoses and all are in place and look good.

At 140,000 miles, I think I'm just going to replace the upstream A/F sensor and downstream O2 sensor with the OEM Denso units, but am having difficulty identifying the correct quantities, locations and part numbers.

I'm sure I'm not the first to go through this and would greatly appreciate some assistance.

 

If you have no vacuum leaks, you may likely you need a new upstream AF Sensor. For AF and Oxygen sensors I go to Denso's web site and get the part numbers specific to my vehicle. This way you can confirm you are getting the right part no matter where you buy. If you do not have one already, I would recommend an Oxygen sensor socket head (usually $10 to $15). The Denso AF and Oxygen sensors come with some anti seize for the threads. When installing the new sensor you want to keep from handling or getting anything on the sensor end of the new unit.

Had P0171 yesterday on my 3.4. It turned out to be a vacuum leak. Note the split on the hose...

 

Everywhere I read that the most common cause is a vacuum leak, so before I spend a couple hundred bucks, I'll re-check my hoses one more time ... thanks.

 

The hose double check showed all good. This morning's drive into town threw a new code, P1133 which is "Faulty Air/Fuel Ratio Sensor Bank 1 Sensor 1". So I took your advise and visited Denso's website for the correct information and saved $60.


Air Fuel Ratio Sensor
Location: Upstream
Denso Part #:234-9001
$119.60
https://www.densoproducts.com/SearchResults.aspx?kw=234-9001

 

I came up with the same part number (

$146 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

234-9001) for your truck. Also, scratch what I said about the oxygen sensor socket... I was thinking of the AF Sensor I recently did in my old lexus. I thought this looked like a good write up on the AF sensor for the Tacoma...

https://www.tacomaworld.com/threads/how-to-replace-o2-sensors.194366/

Good Luck!

 

I found myself wondering what the difference was between the Air/Fuel Ratio and Oxygen sensors and did lots of research, which I will share here.

The Air/Fuel Ratio is a wideband sensor located before the catalytic converter and is much more accurate, than the Oxygen sensor. The AFR provides more feedback to the ECM, so the computer can accurately adjust the mixture for the engine to run cleaner. The O2 is a narrowband sensor, located after the catalytic converter and they should not be interchanged.

The P1133 code I got is typical of a failed heater element in the sensor, which is apparently a common failure with the 1st Gen Tacoma A/F sensors. A simple test with a multi-meter will identify if the sensor is bad.

 

For added info here, 95.5 through 2000 Fed 49 state ('99 Cali) are narrow band O2 both front and rear. The only difference between the part numbers are the length of the cable to the connector.

 

Interesting info, thanks for the clarification.