p0171 cant solve

Ive had this code for about 2 years now and i cant locate the problem. Ive replace the first cat, the bank 1 02 sensor, cleaned the MAF, and cleaned the fuel injectors. I have checked for holes in hoses but found none. One hose looks worn and has some cracking but nothing that looks like it can cause a leak... any ideas on how i could get this to go away? cant get a smog with the light on...

 

Ever had your pre cat exhaust checked for leaks?

 

Replacing a cracked or brittle hose would be a good place to start.

 

Fuel filter if that dont do it then a new fuel pump...
I went through hell with that code on my tacoma, ultimately thes are the two things that fixed it.

 

1. Monitor the fuel trim readings at idle and at 55 MPH driving down the road. If the numbers are low at idle but climb on a part throttle cruise, the airflow meter could be reading low or it may also have low fuel pressure. The mass air flow sensor grams per second should be 3.3-4.7 at idle and 12.9-18.3 at 2500 RPMs no load, if the readings are low the sensor could be bad.

2. Monitor the calculated load reading on a wide-open throttle acceleration. The reading should go to 85% or more. If not, then the airflow meter could be faulty.

3. Monitor the oxygen sensor inputs, both front and rear oxygen sensor signals. The oxygen sensor should not stay high or low voltage for extended periods of time. If the oxygen sensor shows low voltage and the fuel trim readings climb, check the performance of the oxygen sensor.

4. Check the vehicle for a vacuum leak by spraying carburetor spray around the intake manifold while watching the fuel trim readings. If the readings change, there is a vacuum leak.

 

most common problem is replace mass air flow sensor

 

Sub'd. Good info.

 

this is the hose that was slightly worn i taped around the connection i wouldn't think it would cause me to throw that code but what do u think? i tried spraying carb cleaner around several places in manifold and no change in rpm. and ill change the fuel filter next really hoping its not a fuel pump.

 

any at home ways to check for leak in pre cat exhaust?

 

If there is no change In performance on acceleration. I would not suspect fuel pump the cause. It would have to be pretty bad for the truck to not be able to compensate at idle.
Maf sensor is usually the cause. I have changed many maf sensors on many different models of Toyota's. For some reason they get glitchy. Not a lot of success cleaning Toyota maf sensors, replacement is usually neccesary.

 

Yeah no change in performance just the light, so ill replace the MAF as well, I have a OBD II pocket reader as well is there any way i could test the MAF with this?

 

If you can read data with it you can monitor maf data at idle 3.3-4.7 g/s at idle

 

The pcm can usually spot a bad a/f ratio sensor.

 

this is the scanner i use but i dont think it can get that info, thanks ill try to ask a buddy if he has one that can check sensors

 

They have Bluetooth modules really cheap on ebay. One of those and a good cell phone and you can datastream

 

Did you reset the ECU? I know when I cleaned my maf and changed out the temp sensor on the back of the motor it didn't take untill I reset the ECU

 

Reset ecu after any sensor replacement a must

 

Get the obd2 bluetooth reader. It gives you a ton of info!! I love mine! I paid 20 for the reader and 5 for the app.