Chico6

2002 4Runner SR5, V6, 85410 miles
This is my first Check Engine issue with the truck since I bought it in October 2004. Three dash lights (Check Engine Light, VSC and TRAC OFF lights) all lit up at once (on Aug 09, 2008).
Checked battery voltage, cleaned battery posts, and gas cap was tight. Code got erased when I disconnected the battery cables, but after driving 12 miles the Check Engine Light, VSC and TRAC OFF lights lit up again. Got the truck diagnosed. Got code P1135 (Manufacturer Control Fuel Air Metering). Replaced the air fuel sensor (DENSO p/n 89467-35011). I did not erase the codes after installing the new air fuel sensor. Instead, I drove the truck (about 30 miles) and hoped the lights would turn off by themselves, but they didn't turn off that day. The next day, I start the truck and notice the Check Engine Light, VSC and TRAC OFF lights were are all gone (off). (Cooool...I never knew that codes got cleared on their own after replacing the correct part. Now, I am sure the old air fuel sensor had gone bad.)
FYI: I read in one of the 4Runner forums that the heating element resistance on a good sensor should be between 0.8 - 1.4 Ohms at 68°F. The heating element resistance is measured between the two black wires on the air fuel sensor. I checked the resistance (with a Fluke digital multimeter) on the old (bad) air fuel sensor and got a value of 2.3 Ohms at 78°F. The resistance was 1.1 Ohms on the new air fuel sensor at 78°F (within the range, good sensor).
Since installing the new air fuel sensor, I have noticed that the truck does not leave the strong exhaust odor (that it used to) during startup and power during acceleration has improved. I'm sure miles per gallon has improved ,but I haven't taken a measurement yet. In my opinion, I think it is a good idea to change the air fuel sensor sometime after 75K, since it helps the overall performance of the truck so much and prevents possible damage to the catalytic converters (very expensive parts). Also, the air fuel sensor was easy to reach and replace. Good luck and Thanks to members of the forums whose posts on this issue were so helpful.

BigBallsMcFalls

take note

your rear o2 sensor will now, likely puke out in 4 months it is almost a guarantee.

so get
ready to replace it. these things wear out normally in pairs, kinda like a pair of new headlight bulbs. and when the a/f is on the fritz, it accelerates the death of the rear.

also your Denso part number is a Toyota specific part number

you will remove p/n 89467-35010 ...35011 is an upgraded version, so don't worry
when a dealer gives you 35011 it is the correct part ...a/f for 3.4 engine

eric-the-red

I just replaced the sensor on my 01, with 150,000 km on it, in May after getting the P1135 code, . I'm now getting 450 km per tank compared to about 380 km before replacing it. The gas savings should pay for the new sensor fairly quickly.

TOYJOETA

Just finished up my 3.4 swap, and am getting, a P1135 code also. For the air fuel sensor I just reused the old sensor from the 3.0, The engine harness that came with the engine had a shattered connector shell for the 3.4 sensor, which actually is a different style connector shell. So i had another older 3.4 harness that had the same style connector as the 3.0 so I just spliced that one in. are the 2 sensors different? or is the one that I used just a bad one?

Thanks
Late
Joe

TOYJOETA

Well i tested the A/F sensor and it was bad so I had another one laying around so I swapped it in and I'm still getting the same code? is there a difference between the two sensors?

mt_goat

Yes there is a difference between the A/F sensor and the older style O2 sensors. What year and model ECU are you using?

BigBallsMcFalls

if you have to ask, I am guessing you didn't test an Air Fuel sensor correctly.

to test one you need a computer hooked up to the diagnostic port
and monitor the waveform. an a/f sensor function is untestable without
the ECU interpreting for you.

you can only test the heater circuit and
voltage of .64 or .65 without using a computer, and that is garbage
doesn't tell you if it really works or not.

a/f is not like an o2 sensor that you can easily test with a multimeter

TOYJOETA

The ECU is from an 02' tacoma manual trans.

I get that I need a computer to see if the sensor is working, but thats not the code I'm getting, the code is for the heater circuit. I pulled the connector and hooked up my multi meter and am getting 13V at the connector so it must have to do with the difference between the newer and older style sensors, I think?

mt_goat

The 02 Taco definitely takes the A/F sensor for the front.

BigBallsMcFalls

yeah it's not just cali spec anymore

at '02 forward all of them have a/f's

TOYJOETA

that blows, I just priced one at toyota and...$213.00 thats so diculous it ridiculous.

mt_goat

Try here, $149:
https://www.1sttoyotaparts.com/partscat.html

hwkav8r

So, 400 miles after I bought an 02 Tacoma, I got the check engine light (trucks got 120K on it). Tested it, and sure enough it was the air fuel sensor, after reading some of the comments on here, I went ahead and bought it from amazon for about 140 bones. The same day that I ordered it, the light went out on its on and hasn't came back on for the past week. Go ahead and replace it, or just keep it on a shelf for when I get the light again? Thanks-

TheDurk

'01 forward on 4Runners. Cali's only existed in '99 and 2000.

TheDurk

At 120k, it probably slow and giving you suboptimal mileage and it's end-of-life anyway. However, if it's a heater code, I'd probably wait a while to see if it came back. Then I'd be sure the problem was in the sensor if it cured it. If it's an out-of-range signal, I'd just change it. What was the code?

hwkav8r

Thanks for the reply, it gave a P1135 "air fuel sensor heater circuit malfunction". I'm getting 18.75 to 19 mpg based on the last 500 miles.

hwkav8r

It came back, it would come on every other time I'd start it. I changed it out this afternoon. Real curious to see whether it increases fuel mileage.