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Seems logical. If the oxygen sensors indeed fix the problem would return the two purchased from Auto Zone for a full refund noting them as defective or incompatible with the vehicle. By the way, what brand oxygen sensors did you purchase?
 

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Just an FYI, "Circuit HIGH" faults mean the circuit it open. The ECM is sending out a full 5v reference voltage because the circuit is not complete (which is what sets the fault code). You could actually disconnect any know good sensor that uses a 5v ref, effectively creating an open in that circuit, and it will throw a circuit high fault. Its either missing signal return or the vref to the component its controlling. With that said, if you continue to get circuit high faults, its either an internally faulted circuit inside the 02 sensor, OR the wiring between the sensor and the ECM has an issue. You could Ohm out the sensor itself, as long as it shows resistance on that circuit, that tells you its in the wiring between the sensor and the ECM. You would have to further Ohm out the remaining circuit to isolate root cause. Now if it does happen to be the 02 sensor, then i would suspect excessively high exhaust temps damaged the sensor. In my experience.... which may not mean much to any of you, is that 02 sensors don't go bad very often and when they do, its usually because something damaged them. Its usually never the 02 sensor per say, but rather something else that's causing the fault and most people just throw parts at it because they don't understand how it actually works. And i don't mean that toward any of you, its just a general statement from what i deal with on a regular basis in my line of work.
 

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I don't disagree that the sensor could be bad. I thought it unlikely since he replaced them to begin with resulting in no change.

I haven't come across injector problems myself, but the smell of gas with brand new O2 sensors didn't seem to suggest defect of the sensor itself.

So following your train of thought, if it isn't the sensor, then it is possibly the harness that has shorted to ground. It might explain the reset mid-drive. That's why I originally thought "ground."

Reasonable?
 

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If his issue is mainly at cold start up. I think he has 2 different issues, and the 02 sensor is just one of the issues because they aren't controlling fueling at cold startup. They also only control fueling at idle and part throttle.
 

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Well, the problem I still hope is explained is the auto-reset of the trims mid-drive. It doesn't appear that contact was lost with his OBDII adapter given the continuous readings for the other parameters.

I didn't really look at the data from a cold start for your stated reasons since Trims are useless at that point for diagnostics... I'm curious as to why a single O2 sensor would explain both banks being off.

I really thought it might have been a fueling issue, but if the sensor doesn't fix the problem after the 2nd replacement, then the other evidence suggests that the possible short is elsewhere..

FYI... I just like discussing these things... I'm not challenging you (I always feel like I need to throw this in there, but it is usually unnecessary) :D
 

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Discussion Starter #26
Seems logical. If the oxygen sensors indeed fix the problem would return the two purchased from Auto Zone for a full refund noting them as defective or incompatible with the vehicle. By the way, what brand oxygen sensors did you purchase?[/QUOTE

They were denso spark plugs from autozone, about to post new update.
 

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Discussion Starter #27
Just an FYI, "Circuit HIGH" faults mean the circuit it open. The ECM is sending out a full 5v reference voltage because the circuit is not complete (which is what sets the fault code). You could actually disconnect any know good sensor that uses a 5v ref, effectively creating an open in that circuit, and it will throw a circuit high fault. Its either missing signal return or the vref to the component its controlling. With that said, if you continue to get circuit high faults, its either an internally faulted circuit inside the 02 sensor, OR the wiring between the sensor and the ECM has an issue. You could Ohm out the sensor itself, as long as it shows resistance on that circuit, that tells you its in the wiring between the sensor and the ECM. You would have to further Ohm out the remaining circuit to isolate root cause. Now if it does happen to be the 02 sensor, then i would suspect excessively high exhaust temps damaged the sensor. In my experience.... which may not mean much to any of you, is that 02 sensors don't go bad very often and when they do, its usually because something damaged them. Its usually never the 02 sensor per say, but rather something else that's causing the fault and most people just throw parts at it because they don't understand how it actually works. And i don't mean that toward any of you, its just a general statement from what i deal with on a regular basis in my line of work.
I think you are right! I'm about to post an update! Something else is causing this.
 

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Follow the evidence.....

They ruled out injectors, you ruled out O2s, the MAF change will be beneficial given the response but it is not the problem...... Codes reading lean because of misfires.... You've got fuel going into a motor that's not needed and is in excess.

Something is causing that, and the Open Circuit G8One2 has suggested goes to a possible short in that circuit. It's impacting both banks.... Get the multimeter out and start checking harnesses and grounds....

Follow the evidence.....
 

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Discussion Starter #29
If his issue is mainly at cold start up. I think he has 2 different issues, and the 02 sensor is just one of the issues because they aren't controlling fueling at cold startup. They also only control fueling at idle and part throttle.
Problem started after the outdoor temps dropped but actually the problems worsens when it's at operating temperature
 

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Discussion Starter #30
Ok so new update got to the dealership cost was $363 for diagnostic and acdelco o2 replacement. So got in the car started it up ran smooth!. Guy said to drive it around to clear some of the extra gas out since the computer was dumping added fuel. So I drove it around and about 10 min into the drive the cel popped back on" thinking damn it" so went home but car was still driving smooth. Cel was p0172 and p0174. Today drove it seemed fine figured still cleaning the extra gas out the system. Well about 10 min Into drive came to stop light and car started running choppy again at idle on drive. Took off seemed smooth when accelerating, so went back home. Now it's parked outside and I feel like it's goin to do what it did last time and get worse! I'm goin to call them later as i work night shift and i need to get some sleep for shift tonight
 

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Discussion Starter #31
Follow the evidence.....

They ruled out injectors, you ruled out O2s, the MAF change will be beneficial given the response but it is not the problem...... Codes reading lean because of misfires.... You've got fuel going into a motor that's not needed and is in excess.

Something is causing that, and the Open Circuit G8One2 has suggested goes to a possible short in that circuit. It's impacting both banks.... Get the multimeter out and start checking harnesses and grounds....

Follow the evidence.....
Ok tomorrow when I have time I'm goin to pull the multimeter and start testing, I'm wondering if maybe it's the o2 sensor extensions or just one of them sense i have headers so i had to install the o2 extensions hmmm
 

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Good luck, man.

I'm kind of a hands on guy, myself. It's hard to really keep thinking without seeing.
 

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So if its not throwing the circuit high faults, and only the P0174/p0172 faults, those a stuck lean faults. So whats happening is the 02 sensors are reading too much 02 in the exhaust so it dumping fuel to compensate. You see this with your fuel trims pegged at 26%. LTFT are only accuratly reported over a long term fuel adjustments. The only time LTFT mean anything is BEFORE you clear or reset any fueling tables and fault codes. LTFT is not supposed to be more than 10% of your STFT. The STFT is your instant read fueling. STFT on a healty engine should read, and dance around 5%. Stuck lean faults does not mean there is a problem with the circuit. They mean you have a vacuum leak somewhere, or an exhaust leak pre catalysts. Exhaust and intake leaks are not always audible, especially with a louder aftemarket exhaust. A vacuum leak could ALSO be present in your PCV system if its not sealed, installed, routed correctly or pulling air from in front of the MAF. Now I'm not saying any of this is your issue, but if it were my car, Id dig deeper and check these things.
 

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ON a side note, excess fuel can AND WILL foul out your spark plugs. It wont foul them to the point it wont run, but it wont run as good as it should and could idle like crap. Once you get the core issue ironed out, replace the plugs.
 

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I just realized P0172 is a stuck rich fault on the driver side. I thought for some reason they were stuck lean codes for both banks. So what you have is bank 1 stuck rich and bank 2 stuck lean. The only time i have ever seen opposing banks go rich/lean is when the timing was off. I suspect you may have a mechanical issue. You should perform a compression and leak down test on a HOT engine.
 

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Seems logical. If the oxygen sensors indeed fix the problem would return the two purchased from Auto Zone for a full refund noting them as defective or incompatible with the vehicle. By the way, what brand oxygen sensors did you purchase?[/QUOTE

They were denso spark plugs from autozone, about to post new update.
What brand are the oxygen sensors? Were the spark plugs properly gapped and torqued? However, at this point, both answers seem moot i.e. unlikely to remedy the situation. Based on the recent update seems as if the dealership might have been incorrect in their diagnosis.... what that's impossible. Can't begin to count how many times the dealership with supposedly better trained technicians, superior facilities and state of the art diagnostic equipment incorrectly troubleshooted a slew of issues with various vehicles. Am not one to point blame since I have been wrong more times than I like to admit. The point is, I'd rather narrow down the culprit to a range of possibilities from the most to least likely and most to least expensive to replace and go from there. The way I see it, if their diagnostic fee is $100 then why not within reason "throw parts at it" since there are always new things to learn and discover that can only be achieved through real-life experience. Moreover, if a similar issue arises in the future on a different vehicle, then prior knowledge and experience has shown that more likely than not xyz is not the issue. Therefore, in theory, one can draw a conclusion on what is happening more quickly. Guess the old cliche' rings true, six in one hand and half a dozen in the other. Hopefully, the dealership will work diligently to rectify the situation and sorry for brief the dissertation.
 

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Well, there is one difference. Replacing the sensor did register a change. P0171 is gone, and P0172 arrived.

The problem may well be on bank 2 if it is a failure in compression. Rich misfires will make your O2s think the motor is running lean, and if there is a compression issue then combustion failure could explain the difference between the banks. A rough running engine is a misfiring engine.....

Though, what if the compression test was already done and it passed? I gotta think the dealership tech would have already done that. As much crap as we give Dealer Techs (Me included at times)... If a few guys with wrenches, laptops, and ambition can figure THAT out... sufficed to say so too have they.... If not.... I don't see how they'd ever stay in business.

The biggest problem I have with a shop is they'll go through the same steps as I have, and they'll want to do just what I have already done... Then it's another $363 for the NEXT thing.... Oiy vey...... None of this makes any gah'dang sense. :D
 

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Discussion Starter #38
I just realized P0172 is a stuck rich fault on the driver side. I thought for some reason they were stuck lean codes for both banks. So what you have is bank 1 stuck rich and bank 2 stuck lean. The only time i have ever seen opposing banks go rich/lean is when the timing was off. I suspect you may have a mechanical issue. You should perform a compression and leak down test on a HOT engine.
Yeah you could be right and yeah It was weird that one side is rich and other is lean. I know what a compression test is but what is a leak down test.
 

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Update so went out to test some stuff this morning with my multimeter and popped the hood guess what I found.... the gm guy left his fuel pressure gauge hooked up to my fuel rail Lol! Guess he hasn't noticed as they have not called me about it. So any way I wanted to check the o2 extension wires and see if they were ok and then realized something, when I changed my maf I also cleaned my throttle body with the crc throttle body cleaner and I remember something about messing it up if you push the blade in with your hand to clean it. So I took the cai off and checked around for left over residue, disconnected the negative battery cable for 38min. Put cai back on. Started for 3 min. Turned off a min started back for 3 min. Hoping maybe it does the relearn for tb position. Well nothing changed car runs good for a few min or so during start up and idle and then when it warms up its starts to get rough idle symptoms again drove it around the block and its rough again. Codes havent popped back up again as the system reset the cel after battery disconnect. Oh looked at the fuel pressure gauge they left on there and its reading about 64psi off the fuel rail. Attached pic below of fuel pressure gauge left on vehicle when I opened hood. Forgot to take one with car running to show the 64psi reading.
 

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....and then realized something, when I changed my maf I also cleaned my throttle body with the crc throttle body cleaner and I remember something about messing it up if you push the blade in with your hand to clean it. So I took the cai off and checked around for left over residue, disconnected the negative battery cable for 38min. Put cai back on. Started for 3 min. Turned off a min started back for 3 min. Hoping maybe it does the relearn for tb position...
Unlike the G8 V6, the GT doesn't have a do-it-yourself at home no special tools required relearn procedure and believe reprogramming requires a Tech II or equivalent.
 
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