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Got a p0301 code and a p0200 code.
When the engine is cold both O2 sensors show a zig-zag pattern and the engine works OK. After 10-20 minutes the bank 1 o2 sensor shows a steady deal line while the bank 2 sensor still zig-zags.
I don't have any OBD code related to 02 sensors, yet the o2 sensor quits working probably when the exhaust gasses heat it up to operating temp. Am I thinking right that some kind of thermal expansion causes a short or a totally open circuit?
I am about to travel in the van in 10 hours and I am wondering if it is the o2 sensor I should buy in spite of lack of any OBD error codes?
Does my diagnosis make sense? My doubt is that a faulty o2 sensor on bank 1 should throw codes like p0130, p0131, p0132 etc...
Well at first glance I would say your O2 sensors are probably correctly seeing your issue and trying to tell you about it. Very low voltage on sensor 1 says its a very rich mixture, and your fuel trim is also showing -30, which says its taking away as much fuel as possible to try to correct it. Since the DTCs you listed are for a misfire and a fuel injection problem, I would have to guess that you do in fact have a fuel (or spark) related issue causing a misfire. Does it run poorly or smell rich?
Last edited by dtcassist; July 17th, 2020 at 2:26 PM.
Thanks for the reply and for helping me. The exhaust smells normal, no smoke, no sweetish or sour smell.
what puzzles me is the abrupt change in engine behavior. It runs perfect, with full power for 10-20 minutes and then suddenly runs like a tractor for the rest of the day. Like with the flip of a switch. That leads me to believe that maybe it's an electronic problem. If it were a spark plug, a leaking injector or o2 sensor the the engine would be running like crap all the time or alternating between crap and normal irregularly.
what I have is a precise pattern: engine starts like a champ in the morning, heats up to operating temp within a few minutes (california) runs fine for another 10-25 minutes and then suddenly tractor mode for the rest of the day until the next morning. No exceptions.
Watching all of your engine data during this change in behavior would tell you a lot. What changes when this starts running bad? Does the O2 sensor read normally beforehand? Is it going into closed loop operation right when this happens? Do MAF, MAP, temperatures, etc. read normally before and after? If you can see misfire data that would be very helpful in this scenario. Don't know how you are reading data but if it's generic OBDII you won't be able to see everything.
I've seen 'poisoned' o2 sensors that skew readings but I'm not sure i would start there. Short of an obvious answer, you can always swap parts instead of buying new. Spark plugs, wires, coils, from cylinder 1 to 3, or even O2 sensors from bank 1 to bank 2.
Now the situation is developing. Van was running fine and after 200 miles I got stuck in the middle of nowhere. The ecm b fuse keeps blowing. I start the ignition, all is fine, I crank the engine and it works for a few seconds and then dies by blowing the ecm b fuse.
seems like a short circuit but where to look for it. I have little time because during the day it is too hot to do anything at over 100F so I have only a few hours in the afternoon and morning.
You changed injectors on this van, right? Can you unplug those one at a time and see if the short goes away? That would point to the wiring for them being damaged somewhere.
I can't remember, maybe you can't access them easily on this engine, one of GM's bright ideas hides them under the plastic intake cover and I forget if it's the 97-02 or 03-up (or even both)..
July 17th, 2020, 12:27 AM
Real Time Help with probably O2 sensor
