P0171 - Toyota Nation Forum : Toyota Car and Truck Forums

dreameral · 09-07-2007, 05:20 PM

Engine light came on a couple of times on a trip to Myrtle Beach. First time I figured it was the gas cap was loose. I drove all day and topped it up with gas a couple of times. The next day it when out on it's own. On the trip back filled up again on gas and as i pulled out onto the highway and accelerated hard, the CEL appeared again. This time I had my wife take it to a garage and the code was p0171.The mechanic wrote P0171 O2 sensor on the invoice. Does this mean it's the o2 sensor or is he just guessing. I bought the car second hand and there were good records. In Jan 06 the bank 1 sensor 2 was replaced. Any ideas please.

toyotechwv · 09-08-2007, 05:18 PM

Quote:

Originally Posted by dreameral

Engine light came on a couple of times on a trip to Myrtle Beach. First time I figured it was the gas cap was loose. I drove all day and topped it up with gas a couple of times. The next day it when out on it's own. On the trip back filled up again on gas and as i pulled out onto the highway and accelerated hard, the CEL appeared again. This time I had my wife take it to a garage and the code was p0171.The mechanic wrote P0171 O2 sensor on the invoice. Does this mean it's the o2 sensor or is he just guessing. I bought the car second hand and there were good records. In Jan 06 the bank 1 sensor 2 was replaced. Any ideas please.

He's guessing. You need a new MAF sensor. Very common on MZ V6's.

dreameral · 09-10-2007, 03:51 PM

Where would I be able to purchase one online

toyotechwv · 09-11-2007, 07:50 AM

Quote:

Originally Posted by dreameral

Where would I be able to purchase one online

www.trdparts4u.com

TRD VVTi · 09-11-2007, 03:02 PM

MAF sensors don't actually fail that often.

You should try cleaning it.

Use brake cleaner to clean it. Don't scrub it or use anything to touch the filament. Hose it off good with a quality brake cleaner and let it dry thoroughly before reinstalling it.

Some people say to use an electrical contact cleaner but I don't not advise it. Contact cleaners can leave a residue. Do not use carb cleaner or any other cleaner either. Any residue left on the sensor can ruin it.

EDIT: Also note that there could be other causes for that particular code. A faulty oxygen sensor or vacuum leak for example.

***toyomoho*** · 09-11-2007, 07:54 PM

P0171 System too Lean (fuel trim)

The ECU is detecting a lean air/fuel ratio based on info received from the sensors then compared to a theoretical air/fuel ratio. The ECU is adding more fuel to compensate and thinks there is a problem so it sets this code.

Check the following: intake or exhaust manifold leak, injector blockage, fuel pressure, MAF, ECU engine coolant temp sensor, A/F (02) sensor bank 1 or 2 sensor 1.

dreameral · 09-12-2007, 06:04 AM

THe CEL light seems to only come on during a long trip on the highway. Around town it has never come on. It's been a two weeks since it has been reset and still is not on. Does this fit the bad o2 or bad MAF sensor.

toyotechwv · 09-12-2007, 07:09 AM

A MAF sensor is the most common cause for a P0171 in the MZ V6's. Most often than not if it is a bad O2 or AF sensor it will set an additional code.

dreameral · 09-12-2007, 10:12 AM

OK Thanks...I'll look there first

TRD VVTi · 09-12-2007, 11:01 AM

Quote:

Originally Posted by dreameral

THe CEL light seems to only come on during a long trip on the highway. Around town it has never come on. It's been a two weeks since it has been reset and still is not on. Does this fit the bad o2 or bad MAF sensor.

See my earlier post.