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</>I have a 2001 Aurora with a 4.0, 88k miles-was getting first a P0151, then P0174 with the P0151-I replaced the O2 sensors (both upstream) andall codes way for about a week, maybe 200 miles of driving-now I am getting a P1154-here is what they mean:


P0151-sensor circuit low voltage Bank 2 Sensor 1


P0174-System too lean Bank 2


P1154-Heated Oxygen Sensor (HO2S) transition time ratio bank 2 sensor 1 (Front Bank)


It takes a few start/stops for this code to set. I did freeze frame of event and it seems to happen when on expressway driving. There are no drivablilty issues at all. I can not find a clear explaination of what this code means, and don't know where to start. I have a Davis Chip along with a Acton scanner (9145)-the chip is a data logger and the graphs of the O2 sensor (front) show it is switching fast, the center is around .45 volts, which is where it should be. I am getting a good range (low as .1 and highs around .8)-got gas yesterday and am getting 18mpg in combined city\highway driving, it is not running hot (when warmed up it is between 200-215, which is normal for this car)-anybody have any ideas what to look at?
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</>Edited by: mikeaurora

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did you replace the sensor with oe or am? some am sensors will not switch at the correct rate as oe, thus illuminating mil.


ase master


lexus and toyota certified tech.
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transition time+ time between rich and lean switches, its a wave form that you will not be able to see with what you got. You don't have an occiliscope do you? this is probably an af sensor and is slow to respond, you have created this problem, most likely because its the same bank and upstream o2. Sounds like its switching too slow for closed loop fuel control... af + after market, oe= orginal equipment.


ase master


toyota and lexus certified tech.
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does this engine have secondary air injection, common failure on these vehicles, the egr control solenoid that is mounted all both manifolds?
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