Lexus Troubleshooting Questions? Ask a Lexus Expert
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What are the malfunction codes that are set in the computer that turn the check engine light on? Does it ever shift into O/D if you get it on the highway?
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It is going on 1 AM here EST. I need to process this info and get back to you tomorrow. Is this acceptable? If you can get the code number that can be very helpful. Most parts stores like Auto Zone do free code reads.
Let me know how you would like to proceed.
codes are PO300,302,304,306
Short term fuel trilm1 7%
Long term fuel trim 1 -6.3%
ST fuel trim 2 19.5%
LT fuel trim 2 52.3%
ST fuel trim 3 -100.6%
LT fuel trim4 -100.6%
The p0171 is a lean code and the p1150 is a malfunction in the Bank 2 Sensor 1 AFR sensor. The other 300 series codes are misfire codes for the front bank or bank 2. The O/D problem is secondary to these problems. The O/D is temperature sensitive and will not engage until the computer sees the proper coolant temp input.
You need to determine if the AFR sensor is bad and is driving the system lean(not enough fuel) and setting the P0171 code or is the system running lean (intake leak, dirty or contaminated MAF sensor) and the result of this is making the AFR sensor stick with a high voltage and triggering the P1150 code. There are some test that can be done to determine this and one involves using an active testing scan tool. You need to determine which is the cause and which is the effect so to speak. The most common problem is a dirty MAF sensor which makes the system run lean. The only thing that kills this theory is that it usually affects both banks not just number 2. This only leaves the AFR sensor which is also common to go bad on these engines. Focus on the tests for the AFR sensor. It should read 3.3 volts which is equal to 14.7 to 1 fuel ratio. If you shoot some carb cleaner in the intake the voltage should drop immediately on the data list. If you create a vacuum leak it should go up immediately. If it does not and stays fixed then it is bad.
AFR is (Air Fuel Ratio) MAF is (Mass Air Flow)
The AFR is basically a new version of the old O2 sensors.
The MAF is the device that determines the amount of air flow into the engine.