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sprinkles08, ASE Certified Technician
Category: Lexus
Satisfied Customers: 21434
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have a 2002 Lexus ES300 my check engine light came on and

Customer Question

I have a 2002 Lexus ES300 my check engine light came on and off and on and also it was flashing and I was checking my codes in my car I had 7 codes which were P0 174 p 0 300 P0 302 P0 304 P0 440 P0 441 P0 446. When I was looking at these codes I noticed that the po302 and po304 was for cylinders 2 and 4 so I changed out the spark plugs also I noticed that the p0174 code is for the bank 2 oxygen sensor up top. The other codes i know deal with evap. But all this happen after i had been using 87 instead of 93. I also threw pO0420 before but not n these resent codes. If i change our air mass flow sensor, the 2 injectors (2&4), coils (2&4) and Top O2 sensor on bank 2. Will that stop the misfiring.
Submitted: 3 months ago.
Category: Lexus
Expert:  sprinkles08 replied 3 months ago.

Hello and welcome to JustAnswer!

P0174 sets when bank 2 is running too lean and this is most likely related to the misfire codes. It may actually be running too lean or the sensor could be inaccurate and actually causing it to run rich. An exhaust leak could also be causing the sensor to be inaccurate. A localized vacuum leak or restricted fuel injectors can also cause a lean code to set.

Does the exhaust smell any different?
What was the condition of the spark plugs when they were removed?

Customer: replied 3 months ago.
Well it has no smell to it but the plugs were black on the tip. I changed cylinder 2 4 and 6 out. Cylinders 1 was a little white instead of black like the other ones... im gonna check all the hoses and air filter tomorrow. But they said the map sensor can cause this problem as well. It starts up fine but when it get hot then u can feel the shaking and misfiring and the the check light starts flashing
Expert:  sprinkles08 replied 3 months ago.

If the spark plugs were black and it's setting a lean code that points to the upstream oxygen sensor being biased, it thinks the engine is running lean and is adding fuel when it shouldn't be. I'd recommend replacing the sensor with a factory part and that will most likely take care of the issue.

Customer: replied 3 months ago.
changing the bank 2 O2Sensor in the front will fix all that hesitation once the car warms up. And it want feel like its misfiring anymore
Expert:  sprinkles08 replied 3 months ago.

As long as there are no other problems, yes. This needs to be addressed first and go from there.

Customer: replied 3 months ago.
its not the injectors cause i was told it bad injectors or the coils. But like i said when it first starts up its smooth buy once i drive it on highway i can feel it like its misfiring and the the check like starts flashing then stop.. i looked at the map on top of houses of air fliter it looked clean
Expert:  sprinkles08 replied 3 months ago.

Injectors are a possible cause for running rich or poorly but based on the information you have supplied I would recommend replacing the upstream oxygen sensor on bank 2. You need to start there if that bank is running rich and is setting a lean code.

Customer: replied 3 months ago.
Ok just changed the O2Sensor up front/ top by radiator but i didnt drive it let it run cleared the codes first before starting it. It ran for about 5mins i scanned it and only a p1150 code was in it... but that the same part i just changed. So do i need to drive it or what...
Expert:  sprinkles08 replied 3 months ago.

You didn't mention this code before. Is this new now that the sensor has been replaced?

Customer: replied 3 months ago.
Expert:  sprinkles08 replied 3 months ago.

Where did the sensor come from?

Customer: replied 3 months ago.
O'Reilly's Auto Part I'll put it in this morning and reset the codes brand new car for about 5 minutes plug to scan and backup and p1150 was was in there the only code. Since then I've drove the car after resetting the codes and the car has been running fine haven't put it on the expressway yet but as far as the hesitation and a feeling of misfiring is gone so do you think the oxygen sensor was the problem that was causing all this since there hasn't been any problems since I've been driving it I drove it for about 25 minutes
Expert:  sprinkles08 replied 3 months ago.

I do believe the oxygen sensor was the problem and the aftermarket sensor is likely the cause of the code that's currently setting.

After more driving is the code still setting?

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