P0137 o2 slow? - Toyota RAV4 Forums
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#1 (permalink) Old 07-21-2013, 04:45 PM
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P0137 o2 slow?

I introduced myself earlier in another forum, but I'll recap. I'm 57, ASE CMAT l1 with over 35 years professional experience. I am a Missouri Recognized Repair Technician, and am our shop's check engine light/drivability diagnostician. This past Wednesday evening, I fired up my wife's 2010 RAV4 (4 cylinder) and was presented with a MIL. Wonderful. Something for me to repair on my day off. I found a code P0137, meaning the rear O2 had low voltage. Checking my AllData (SomeData) and Mitchell at work, I found no service bulletins for this code. I cleared the code, and have driven the vehicle over 200 miles without the light coming back on. My information says this is a two trip code, meaning the PCM has to see low voltage from the rear O2 for two trips. The dealer does not stock this O2 which means it is not a common part to fail. My wife went against my wishes last week and filled up with a lower quality fuel. I always buy Quiktrip fuel. She put in some Motomart junk, and I'm thinking that might have been the cause of the low voltage. But why wouldn't it affect the front O2 as well, or pop a fuel trim code? I've been diagnosing and repairing check engine lights since 1981, and this stumped me. Any thoughts from the members here? If the cat was going bad, I would assume the volts would be high. Another thing that puzzles me is that the light popped on right when I started up the RAV4. Immediately. I'm thinking programming, but why now? Why not at 40K unless the rear O2 has deviated and is supplying lower voltage and the threshold for the code to set is too high. Also, my wife had just driven the RAV4 from work, about a 20 minute drive, not more than 45mph all the way. The RAV4 sat in the driveway for about an hour then when I started it, the light popped on. VSC and 4WD were on also, but that is to be expected. I graphed the rear O2 using my great Techstream Lite cable, and the waveform looks great. If the code resets, I'll look at the freeze frame (oops - forgot the first time) and then get on the highway and ride shotgun to really get a look at the waveform.

2010 RAV4 2.5 4WD 60xxx miles

Thank you

Tom Guelker
ASE CMAT L1 MRRT
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#2 (permalink) Old 07-21-2013, 07:47 PM
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After I replaced 2006 2.4L's O2 sensor, I realized I did not need to know all the reasons.
Simply replacing the suspicious part removed all the puzzles.

Oxygen Sensor (Rear) changed for 2.4L I4
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#3 (permalink) Old 07-22-2013, 08:54 PM
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[QUOTE=sean20202020;1203425]After I replaced 2006 2.4L's O2 sensor, I realized I did not need to know all the reasons.

Perhaps you don't know it, but my profession is auto mechanic, specializing in check engine lights and drivability. I NEED to know all the reasons.

Mine : 2009 Avalon XL Magnetic Gray Metallic
Hers : 2010 RAV4 Base 2.5 AWD Pacific Blue Metallic

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#4 (permalink) Old 07-23-2013, 12:55 AM
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This is what I meant... I realized I did not need to know all the reasons.

This CEL up and downs are involved with the ECU programming and O2 sensor's intermittent strange signals. It's hard to know how each auto manufacturer programmer set the ECU parameters to turn on and/or off the CEL for the O2 sensor's signal, that fluctuates when it is going to fail. Unless we have the ECU program source codes, it's just only guessing.
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