fault code...p0174

[danewilson77]

Hehe......It should be an easy fix, when you find it bro.

[Johnmadd]

Valve cover gasket can create some really significant failures, check spark plugs for oil, vacuum leaks are also verypossible from the vcg.

[LivesNearCostco]

And if you already replaced the lower boot when you did the CCV, verify all the boots and MAF connected up tightly. IIRC that is MAF to upper boot, upper boot to plastic coupler, plastic coupler to lower boot, and lower boot to TB. If the boot is not fully seated on the TB/coupler/MAF when you tighten the hose clamps, extra air could be sneaking in after the MAF even though you tighten down all the hose clamps. On top of those main connections there is lower boot "thumb" to ICV and "F" connector to upper boot, plus the two little hoses to the "F" connector.

I think the DME controls fuel pulses based on a combination of the MAF reading and how wide the TB is open, then fine tunes fuel mix based on pre-cat O2 sensors. If there is an intake leak after the MAF, the DME sees one or both banks running lean and tries to adjust. If it can't adjust easily it throws a lean code. If the pre-cat O2 sensors become too "slow" to adjust to changing A/F ratios, that can also lead to a code.

You might be able to use the scanner to watch the Bank1/Bank2 O2 sensor voltage fluctuate. You'd want to verify they fluctuate around whatever voltage indicates the "ideal" A/F ratio, which might be 14.7:1, and the values should cycle up and down at some speed. So an O2 sensor that shows the proper resistance (or voltage, not sure which is used with O2 sensors) still could be bad if it can't change it's output as fast as the A/F ratio changes.

[llll1l1ll]

That lower boot sometimes looks like it's on and seated correctly, but it's actually not and is trolling you. So just make sure it's on right before you go and button everything up.

[Scorpius]

UPDATE:

Ok well I got tons of good tips, so i'm not discounting them. VCG and the CCV....well...I'd just done both of those within the last few months so knew it was very unlikely either of those, especially since i pretty much go back in with new parts on everything when i do something.
So knew my intake system was properly seated and tightened as i checked and double checked as i put it back together. Also too new to develop a tear.
So....i reset the codes took off my air intake found some very small pieces of what appeared to be leaves around the edges of the screen on the MAF. I cleaned those out with 60 PSI and then cleaned the MAF. put it all back together and 500 miles later no code returned. So perhaps something was providing a false resistance there?
The only other thing i have noticed (forgive me i don't recall the sensor) but with my code reader i looked at the o2 sensors there are readings on like 4 different pages which all appear to be the same readings, just different values. not sure 100% what each screen is for, but did notice on the very first one the minimum detected value is closer to the trigger value than the other o2 sensor readings, so....i suspect that one is on it's way out and may have dipped (possibly worsen the colder the weather at startup???)
So at some point....i'll be dropping $600 to get all 4 sensors and replace them. thank goodness it's not the MAF.
If anyones interested i can at some point grab pen and paper and copy my readings and screen numbers. from what i can tell there are static max/min values then there are values that are read that show the highest / lowest reading obtained since last reset. if they exceed the static value i would guess the light would throw a fault. but just a guess.

[LivesNearCostco]

Again I've never used a scanner to read O2 sensor values, but I think you have 4 screens for the 4 O2 sensors, and the two pre-cat sensors should show different numbers than the two post-cat sensors. The post-cats should show more air, less fuel because some leftover fuel was converted to CO2 and in the cats.

Wikipedia sez: "The zirconium dioxide, or zirconia, lambda sensor is based on a solid-state electrochemical fuel cell called the Nernst cell. Its two electrodes provide an output voltage corresponding to the quantity of oxygen in the exhaust relative to that in the atmosphere. An output voltage of 0.2 V (200 mV) DC represents a "lean mixture" of fuel and oxygen, where the amount of oxygen entering the cylinder is sufficient to fully oxidize the carbon monoxide (CO), produced in burning the air and fuel, into carbon dioxide (CO2). An output voltage of 0.8 V (800 mV) DC represents a "rich mixture", one which is high in unburned fuel and low in remaining oxygen. The ideal setpoint is approximately 0.45 V (450 mV) DC. This is where the quantities of air and fuel are in the optimum ratio, which is ~0.5% lean of the stoichiometric point, such that the exhaust output contains minimal carbon monoxide."

Assuming the scanner shows O2 sensor voltages (and not A/F ratio), your pre-cat sensors should cycle around 0.45V (450 mV) and the post-cat sensors should show slightly lower than that.

[Newjack]

My car just gave me the P0171 and P0174 codes. I'll be looking into the culprit later when I have time. Is my car driveable right now? I don't know if this will mess up anything like the cat or MAF any further.

[kayger12]

She's driveable.

Probably an intake boot. Those codes typically mean you're getting more air in the combustion chambers than what's being measured at the MAF.

[Newjack]

She's driveable.

Probably an intake boot. Those codes typically mean you're getting more air in the combustion chambers than what's being measured at the MAF.

Thanks Kayger, that's what I wanted to hear. Been driving all afternoon without any codes coming back so that's good news. Still taking a peek tomorrow.

LG Revolution + Tapatalk

[danewilson77]

Thanks Kayger, that's what I wanted to hear. Been driving all afternoon without any codes coming back so that's good news. Still taking a peek tomorrow.

LG Revolution + Tapatalk

Look for a crack in the boot. You can even tape it up until you get a new one... Once you find the crack.

HTC Thunderbolt+TT