sha4000

iTrader: (1)

Yeah a hole on that piece would not affect the car since it's before the MAF like he said.

qewani1

We will not call it a vacuum leak!
MAF reading will be accurate on Idle, but while driving, reading will not be accurate, since most of air will not pass through MAF due to the hole on air inlet... which means fuel trims readings will be high.
Temporarily i have covered the hole with adhesive tape

After driving for a while.. am getting only these 2 codes
P0300 - Random Misfire
P0155 - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1

I have cleared codes & did ECU reset 2 times, but again same codes are coming back...so shall i replace the sensor?
Last time i replaced those pre CAT sensors is before 100k miles

I believe P0300 is coming due to Faulty oxygen sensor

Yamae

I don't think so. Usually P0300 and P0155 are not related each other. I bet you have two different problems.

There is a way to confirm it. Put a resistor 33ohm-330ohm in parallel with the heater lines. This will not cause P0155 but P0300 still turns on. The resistor value is not very strict. The purpose to put a resistor is to cheat the ECU that the heater is not open.

sha4000

iTrader: (1)

The misfire is on bank 1 and the sensor code is on bank 2 so They are probably unrelated. I really doubt any holes on that side of the MAF will affect your fuel trims.

qewani1

Guys fuel trims reading are lower after covering the hole with adhesive tape, so yes it has effect!
Now these are my fuel trims readings on idle:
STFT B1 = 3.9 %
LTFT B1 = 14.8 %
STFT B2 = 3.1 %
LTFT B2 = 7.8 %

There are improvements specially on LTFT B2 readings ( which was 19 % before)

Currently am getting only P0155 no more miss fires codes (P0300)
As per above article, I thing i need to replace ECT sensor since temp gauge needle (after driving the car for 20 minutes) is sometimes reading between 2nd & 3rd line, while in some other times it reads a little above 3rd line (which i guess the correct reading).

Coolant level is full, already checked, using red coolant.

Do i need to replace ECT sensor?
Does a used one works?

Yamae

A slow temperature rise is mostly caused by a worn thermostat. The ECT sensor only detects the temperature. It doesn't have a long time constant. It only has about 10 seconds of it.

qewani1

Yamae when engine reaches normal temp, what should be the reading of the engine temp?, i can check the reading using OBD tool, then we can confirm either its working or not

sha4000

iTrader: (1)

The O2 sensor code would be the likely culprit of bad fuel trims. Have you tried cleaning your MAF.

teaman908

I'm having this same issue too to where my motor is misfiring in all even numbers: 2, 4, 6, and 8 (passenger side). I tried replacing the spark plugs and that didn't work. I noticed 3 out of 4 on the passenger side of these plugs were wet with oil.
I just got some new ignition coils this week and will be replacing all 8 tomorrow morning. I hope everything goes well after this.

If all goes sour then my next component to touch is the PCV valve. I'll try cleaning it out by drowning it in engine degreaser before I buy a new one.

So far it has been misfiring to where the car shakes. It feels like a hot rod lol. Horrible. This motor has 233,xxx miles.

TMaxxTim

That is most likely your oil control valve on the passenger side for the VVTi. I had the exact same issue...change that out before you do anything else.

qewani1

Still getting only P0155
Cleared the code, replaced B2S1 with a junkyard O2 sensor, again same code returned!
Have googled for this error and saw that people recommending to check the fuse

Could i know the fuse location?

Will try swapping the sensors also if i get the special O2 socket

qewani1

Checked repair manual could not see anything about oxygen sensor fuse! So i guess no fuse for these sensors in ls400...
Today have swapped oxygen sensors, will see if code P0155 move around or not!
I have noticed that both sensors have different numbers
89465-500150 this is for OSB1
89465-500060 this is for OSB2

OSB2 is the one with throwing code P0155

After cleaning air mix path located above TB, which was fully blocked with carbon my fuel trims reading came down to below numbers ( thanks to Yamae' s post)
STFT B1 = 0.8 %
LTFT B1 = 2.3 %
STFT B2 = 3.1 %
LTFT B2 = 3.9 %

Guys i need few help with these data as well
When engine reached its normal operating temperature after driving the car for 20 minutes,
Then on Idle ...
what should be the Engine coolant temperature reading?
& what should be the Intake Air temperature reading?

BTW weather Temperature in my area is 25 celsius

Yamae

P0155 is mostly caused by the open heater in the O2 sensor. You need to replace it. Sometimes a connection/connector problem is there but it's quire rare among Toyota cars.

The temperatures you asked are:
The Engine coolant temperature; around 85 degrees C.
The Intake Air temperature; The ambient temperature + several more degrees C.

Yamae

The heater can be checked easily using a circuit tester measuring the connector pins.
See below. The resistance between pin 1 and 2 should be about 10 ohm or so. Yours must be open and shows ∞. If not so, check connectors and wires to it from the ECU.

teaman908

Damn, I wish I could've read this sooner. I just threw $300 out the window and the problem is still not solved. Now to order an OCV valve. Thanks for the advice!