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P0174 Code Help

Old 11-12-2018, 05:34 AM
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P0174 Code Help

My 97 Maxima had a check engine light on. The code that came up is P0174. I had a pretty wicked exhaust leak down at the back end of the car near the muffler so I repaired it and cleared the code. That was about 3 weeks ago. I don't drive this car very much. Maybe 3 times a week back and forth to the train station or the gym. Anyway.. I needed to get the emissions done on the car and even though the CEL isn't on.. it failed. They told me that it takes 50-75 miles for all the codes in the computer to reset in the car and some of them weren't ready. I am pretty sure that the light is going to come back on and the code is going to be P0174.
I searched the forum and I can't find a definitive answer stating what I need to replace. I think its an O2 sensor but I am not sure.
Thanks!
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Old 11-12-2018, 09:12 PM
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your fuel mixture is too lean, i just went through this nightmare but i had multiple codes and an intake leak. scan for codes and see which one it is, if the sensor isn't reading right the mass air flow sensor will read that it's under reporting telling the ecu that a lot less air is entering the engine than probably is.
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Old 11-13-2018, 01:06 PM
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Originally Posted by max ride 41 View Post
your fuel mixture is too lean, i just went through this nightmare but i had multiple codes and an intake leak. scan for codes and see which one it is, if the sensor isn't reading right the mass air flow sensor will read that it's under reporting telling the ecu that a lot less air is entering the engine than probably is.
The only code that this car threw is P0174. Its the only one that came up on my OBDII scanner.
I cleared it 3 weeks ago so there is no CEL.
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Old 11-13-2018, 01:10 PM
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Let me also say that the car runs perfect with no issues at all. Currently there is no CEL on.
I just would like to know what needs to be repaired when the car throws a P0174 code.
I have been told its an updraft O2 sensor, or a vacuum leak or a fuel pump or a fuel filter or the IACV, or the MAF etc.....
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Old 11-13-2018, 01:42 PM
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My guess is bank 2 o2 sensor

Check the easy stuff first..like vacuum leaks and cleaning the maf..but my googling is saying o2
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Old 11-14-2018, 04:59 PM
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Vacuum leaks, exhaust leaks, faulty injectors, gas leaks, misfiring, faulty maf, faulty heated front o2 are causes of the obscure 174. I would double and triple check for leaks front to back, get readings from the o2 and maf sensors, and go from there.
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Old 11-26-2018, 05:53 AM
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OK, So I drove the car about 40 miles over a few weeks and I took it back to the emissions shop. They failed it again because all the sensors still hadn't reset.
They told me to drive the car another 100 miles and bring it back. When I got to 80 miles the check engine light came on. I scanned it with my OBDII scanner and it comes back P0174 again.
Car runs perfect with no issues other than the CEL being on and it failing emissions because of it.
If I bring it to a shop I know exactly what will happen. Mechanics nowadays don't diagnose problems, they just throw new parts in until the problem goes away. They will hit me with a MAF, injectors and all kinds of stuff. I can almost guarantee it. The last time I brought this car in for a repair I couldn't figure out.. 3 different highly reputable shops told me that because the car had 180,000 miles on it.. the reason it was billowing out white smoke and running terrible was because the motor was shot. I told them that car went from running perfect to running terrible overnight. It couldn't be the motor because if the motor was shot it would be a gradual thing. I posted my issue up on THIS FORUM and 2 people instantly responded that it sounded like the fuel pressure regulator was faulty and dumping fuel and the white smoke was unburned fuel. . It was around a $20.00 part at Auto Zone. I replaced it. That was 3 years ago. Car has run perfect since. I rely on this forum for repairs to this car. I have owned it for about 8 years now. The car even saved my life by getting me to the emergency room when I had a massive heart attack at the gym. Its one fast sucker!
Any help is appreciated. If you guys think its the O2 Sensor then that's what I will replace.
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Old 11-26-2018, 10:21 AM
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Change the O2 sensor, clean the MAF, clear your codes with your code reader and put TC-W3 in your gas... 1 ounce to 5 gallons of gas. You should easily pass if your codes are cleared.
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Old 11-27-2018, 09:28 AM
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I ordered the Upstream O2 sensor yesterday. Also my temperature gauge stopped working so I am sure I probably need to order a new sending unit.
Question.... If I install the new O2 sensor... will my CEL turn off on its own eventually? The reason I am asking is I only drive the car about 25 miles a week and I was told it could take up to 150 miles for the computer to clear if I shut the light off with my OBDII scanner.
I need to get the car to pass emissions asap.
Any suggestions?
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Old 11-28-2018, 08:52 AM
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Originally Posted by jgcable View Post
I ordered the Upstream O2 sensor yesterday. Also my temperature gauge stopped working so I am sure I probably need to order a new sending unit.
Question.... If I install the new O2 sensor... will my CEL turn off on its own eventually? The reason I am asking is I only drive the car about 25 miles a week and I was told it could take up to 150 miles for the computer to clear if I shut the light off with my OBDII scanner.
I need to get the car to pass emissions asap.
Any suggestions?
If you use your OBDII scanner, the code is cleared immediately.
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Old 11-28-2018, 09:16 AM
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not sure a big difference in upstream vs downstream, but i just changed downstream o2 sesnor, and light didn't go away after 200 plus miles, i cleared code with scanner, and hasn't come back.
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Old 11-28-2018, 01:01 PM
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Originally Posted by jgcable View Post
I ordered the Upstream O2 sensor yesterday. Also my temperature gauge stopped working so I am sure I probably need to order a new sending unit.
Question.... If I install the new O2 sensor... will my CEL turn off on its own eventually? The reason I am asking is I only drive the car about 25 miles a week and I was told it could take up to 150 miles for the computer to clear if I shut the light off with my OBDII scanner.
I need to get the car to pass emissions asap.
Any suggestions?
You can clear the code with your scanner, but you will still need to drive in order to pass inspection. Otherwise the Not Ready monitors will fail you.
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Old 11-28-2018, 06:16 PM
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Originally Posted by maxima297 View Post
You can clear the code with your scanner, but you will still need to drive in order to pass inspection. Otherwise the Not Ready monitors will fail you.
This is true. Some states will allow 1 or 2 not ready monitors while some states won't allow any. Best to drive it for a bit and check that all monitors are ready. Also, check your state laws.
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Old 01-10-2019, 05:20 AM
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Originally Posted by PH98I30 View Post
Change the O2 sensor, clean the MAF, clear your codes with your code reader and put TC-W3 in your gas... 1 ounce to 5 gallons of gas. You should easily pass if your codes are cleared.
Did all this... after 300 miles of driving some of the systems still read NOT READY and.... after 120 miles of driving after changing the O2 sensor the SES light is still on.
Forum members told me that the SES will clear on its own. Doesn't appear that its going to do that. I already failed emissions twice because there are systems NOT READY (because I cleared the ECU with my OBDII scanner 300 miles ago) and because I am still showing fault P0174 with my SES light still on even after driving it under all kinds of conditions for the last 120 miles after changing it.
Car has no symptoms at all other than the light being on. It runs perfect, idles perfect and shows no signs of any leaks or issues. It just turned 180,000 miles. Every one of them being trouble free until this stupid light came on that I can't fix.
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Old 01-10-2019, 05:29 AM
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I guess I need to go back over this stuff again just to make sure I didn't miss something...

Clean MAF again
Check for vacuum leaks
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Old 01-10-2019, 10:56 AM
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If that is the front bank lean code, i get that if i idle the car for a long period of time. If i clear it, it won't come up unless i idle again for an extended period. No idea why this pops up. Regarding the not ready issue on smog, my smog guy told me it was very common on this car to have that issue so he overlooked it when i did mine.
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Old 01-10-2019, 11:48 AM
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You may already have a tool like this but there's an OBDII scanner (not just a code reader) you can buy which provides real-time OBDII data off your vehicle's bus. This might give you more insight into what is throwing the code, though nothing is guaranteed:

I bought the following:
Amazon Amazon
BAFX Products Bluetooth Diagnostic OBDII Reader/Scanner for Android Devices

I have the torque pro app on an old android tablet; gets the job done. This manufacturer also makes a "wifi" version that supposedly works with iOS; haven't tried it. There are also other options out there; here's a rather old thread about it:

https://maxima.org/forums/4th-genera...ol-advice.html

You may have already looked into this but if not, it might get you pointed in the right direction!

Last edited by Shrout1; 01-10-2019 at 11:53 AM.
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Old 01-10-2019, 12:37 PM
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Originally Posted by Shrout1 View Post
You may already have a tool like this but there's an OBDII scanner (not just a code reader) you can buy which provides real-time OBDII data off your vehicle's bus. This might give you more insight into what is throwing the code, though nothing is guaranteed:

I bought the following:
https://www.amazon.com/gp/product/B005NLQAHS BAFX Products Bluetooth Diagnostic OBDII Reader/Scanner for Android Devices

I have the torque pro app on an old android tablet; gets the job done. This manufacturer also makes a "wifi" version that supposedly works with iOS; haven't tried it. There are also other options out there; here's a rather old thread about it:

https://maxima.org/forums/4th-genera...ol-advice.html

You may have already looked into this but if not, it might get you pointed in the right direction!
I have something similar. It is telling whats ready and whats not ready. 3 systems still read NOT READY. That's one reason it failed emission. The other reason is P0174 which tripped the SES light.
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Old 01-10-2019, 03:24 PM
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Check the accordian-looking air intake boot between the MAF and the Throttle Body for splits and/or leaks that would allow un-metered air into the system (resulting in lean condition).
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Old 01-13-2019, 06:31 PM
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OK, I checked the entire engine compartment for leaks or splits using a propane torch. There are no leaks or splits of any kind.
Code P0174 is still present. MAF is clean, upstream O2 sensor has been replaced. I have driven almost 300 miles and the following systems are still NOT READY.
O2 Sensor, CAT and EVAP.
I have driven about 180 miles since I changed the O2 sensor. I was told the SES light would eventually shut off. Well.. its not.
Any other suggestions?
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Old 01-13-2019, 08:00 PM
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You've got two different things going on - Lean Condition, and Codes Not Ready.

Re: lean: Same thing I told Dozer Dave re his stalling issue, "what is your observed fuel pressure"? The electric fuel pump is 20 years old, that's a long time...

The light isn't going to go off and the O2 sensor isnt going to report Ready until it's not running lean.

Re: EVAP not ready - this takes FOREVER to set under Perfect, New conditions. Disconnect the EVAP box hoses - is there charcoal in it? If so then there's certainly charcoal all the way up the line to the IACV valve - this charcoal blockage interferes with the EVAP reporting Ready. Fix is to replace the charcoal box and blow out / clean all charcoal from the lines.

I recently fixed both of these problems on my 98 in the manner proscribed.



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Old 01-18-2019, 06:26 AM
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Originally Posted by reallywildstuff View Post
You've got two different things going on - Lean Condition, and Codes Not Ready.

Re: lean: Same thing I told Dozer Dave re his stalling issue, "what is your observed fuel pressure"? The electric fuel pump is 20 years old, that's a long time...

The light isn't going to go off and the O2 sensor isnt going to report Ready until it's not running lean.

Re: EVAP not ready - this takes FOREVER to set under Perfect, New conditions. Disconnect the EVAP box hoses - is there charcoal in it? If so then there's certainly charcoal all the way up the line to the IACV valve - this charcoal blockage interferes with the EVAP reporting Ready. Fix is to replace the charcoal box and blow out / clean all charcoal from the lines.

I recently fixed both of these problems on my 98 in the manner proscribed.



EVAP and IACV are both clear. They weren't clogged. Fuel pressure is around 39lbs which I believe is correct.
Car has absolutely no issues in starting, idling or running. It drives like a new car.
After over 300 miles.... I am still showing EVAP, O2 and CAT "NOT READY" on my OBDII scanner.
I also still have my SES light on showing only 1 code. P0174

I just got a letter from the DMV telling me my car is overdue and they charged me another $20.
At this point.. I am at a loss on what to check.
Its been 80,000 miles since I changed the spark plugs. Could that be it? I usually don't change plugs unless I experience a decrease in performance or fuel economy and for the last 180,000 miles this car has run beautiful.
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Old 01-18-2019, 09:33 AM
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Originally Posted by jgcable View Post
EVAP and IACV are both clear. They weren't clogged. Fuel pressure is around 39lbs which I believe is correct.
.
http://boredmder.com/FSMs/Nissan/Maxima/1997/EC.pdf

Page EC-26

"39" is definitely a number in between 43 & 34 for sure. When I tested my own original unit (https://maxima.org/forums/4th-genera...ogether-2.html) I observed the following measurements:

Old pump: 28 psi idle / 18 "on"
New pump: 36 idle / 44 "on" **Winner!**

I also tested the FPR:

Idle, Capped vacuum line, 0 inches vacuum at FPR: 46 psi
15 inches at FPR: 40 psi
25 inches at FPR: 35 psi


Going forward its up to you to know that your fuel pump and FPR are cutting the mustard.

Have you ever had the injectors out , or replaced ? Could you LIM be rotted ?

You mentioned a propane torch. I instead used a liquid choke cleaner to diagnose air intake leaks. Does propane cause RPMs to rise in the same manner (not sure) ?

In what state do you reside ?
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Old 01-18-2019, 11:24 AM
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80k on a set of plugs is a lot. The car would probably run better with a new set. Yet the problem codes would relate to misfire. So I doubt that changing them would fix your 174 issue.
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Old 01-24-2019, 07:20 AM
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I gave up trying to figure it out. The EVAP, O2 Sensor and CAT all still read NOT READY after over 300 miles of driving. The SES was still on showing P0174
I cleared the code and I am going to drive it and see if the light comes back on and if the systems finally clear.
I have no idea what is wrong with the car. The only thing I do know is the car runs perfect with no issues at all. Only the SES which is preventing me from passing state emissions and ruining my day.
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Old 01-24-2019, 01:11 PM
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Originally Posted by jgcable View Post
I gave up trying to figure it out. The EVAP, O2 Sensor and CAT all still read NOT READY after over 300 miles of driving. The SES was still on showing P0174
I cleared the code and I am going to drive it and see if the light comes back on and if the systems finally clear.
I have no idea what is wrong with the car. The only thing I do know is the car runs perfect with no issues at all. Only the SES which is preventing me from passing state emissions and ruining my day.
Perhaps there are some road conditions it has not experienced since you replaced stuff.
Perhaps changing your driving route, or aggressive acceleration might help.
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Old 01-24-2019, 01:20 PM
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What's your MAF g/s look like? I'll try to dig out my bluetooth OBDII scanner tonight. Have to find it.

https://mechanics.stackexchange.com/a/7958/6756
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Old 01-24-2019, 05:19 PM
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Maybe it's just the ECU. My Maxima was throwing codes P0440 and P0446 at me for a whole year even after I fixed ALL of my evap leak problems. One day, after not fixing it in a year and a half, the code just disappeared out of driving. I only drove it every other day.

In your case, make sure the intake boots aren't torn. After you do your repairs or inspections, just keep driving it. Make sure you go uphill and engine break the car a lot too.
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