P0145 and P0325
P0140 and P0325
Got these engine codes after my "service engine" light came on... they mean "O2 sensor malfunction" and "Knock sensor malfunction"... are these things connected? how do i fix it? is it just a replacement? thanks guys..
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Ketchup83se01
- Posts: 7
- Joined: Sun Apr 13, 2008 5:57 pm
- Car: 2001 Nissan Maxima
Re: P0140 and P0325 (Gman8990)
Have you tried resetting it?Or has it been on for awhile? The knock sensor is kind of a pain to do, o2 sensor is easy to replace.
Re: P0140 and P0325 (Gman8990)
I'll say it again and again, but some people think I'm nuts, just bypass the Knock sensor. Of course after you do this you can only run premium 91, but who on here doesn't run premium? There are wonderful write ups on replacing the KS and I followed them to the letter only to get a KS code within a week of installing the new KS. Why? Because, as engine's get older, they develop more noise and ticks and twangs. So, the KS thinks there is piston knock, when actually, there isn't.
The o2 malfunction can be a couple things. One is if you just replaced some exhaust component, like a new y-pipe, you will get an o2 malfunction. I think your first step is to clear the codes and see if they come back. Then if they do, you will probably need to replace the o2 sensor.
The o2 malfunction can be a couple things. One is if you just replaced some exhaust component, like a new y-pipe, you will get an o2 malfunction. I think your first step is to clear the codes and see if they come back. Then if they do, you will probably need to replace the o2 sensor.
Re: P0140 and P0325 (rxm6)
Im a little noobish so what do you mean when you say i can only run "premium 91"?
Re: P0140 and P0325 (Gman8990)
There are three qualities or octane ratings of gas
87, 89, and 91 (in america anyway, i think canada has 94)
91 is "premium" and is used in high compression engines for more performance and to avoid premature combustion, i.e. the gas ignites from being compressed, like a diesel engine, before the piston reaches the top of its stroke and before the spark is applied. This is a bad thing and will really screw up your engine. So, Nissan installed a knock sensor . The moment the KS hears a potential knock, or premature ignition of gas, it will immediately retard timing and run the engine rich. It will then gradually increase timing to a point where it begins to hear a knock and then retards timing again until it gets it just right. This happens all throughout the time you are driving and a bad KS will just retard the timing and leave it there, giving you poor gas mileage and possibly poor emissions as well. This all relates to the octane of the gas because the higher the octane rating, the more the engine can compress the gas before it explodes on its own. So Maxima's with a properly working KS would be able to run 87 or 89 because the KS would hear the knock and retard the timing. Maxima's with no KS would only be able to run 91 because the timing would be fully advanced and would not be able to sense knock. The upside to this is that you will always have good gas mileage and good performance. The downside is that if you let your mother drive the car and she fills it for you with anything other than 91 you will have knock. Of course if this happens you can always unplug the KS and the ECU will revert automatically to fully retarded timing.
87, 89, and 91 (in america anyway, i think canada has 94)
91 is "premium" and is used in high compression engines for more performance and to avoid premature combustion, i.e. the gas ignites from being compressed, like a diesel engine, before the piston reaches the top of its stroke and before the spark is applied. This is a bad thing and will really screw up your engine. So, Nissan installed a knock sensor . The moment the KS hears a potential knock, or premature ignition of gas, it will immediately retard timing and run the engine rich. It will then gradually increase timing to a point where it begins to hear a knock and then retards timing again until it gets it just right. This happens all throughout the time you are driving and a bad KS will just retard the timing and leave it there, giving you poor gas mileage and possibly poor emissions as well. This all relates to the octane of the gas because the higher the octane rating, the more the engine can compress the gas before it explodes on its own. So Maxima's with a properly working KS would be able to run 87 or 89 because the KS would hear the knock and retard the timing. Maxima's with no KS would only be able to run 91 because the timing would be fully advanced and would not be able to sense knock. The upside to this is that you will always have good gas mileage and good performance. The downside is that if you let your mother drive the car and she fills it for you with anything other than 91 you will have knock. Of course if this happens you can always unplug the KS and the ECU will revert automatically to fully retarded timing.
Re: P0140 and P0325 (rxm6)
There is no way im paying that much money for gas... how much is a KS gonna run me? and where is it?? also, the O2 sensor... where is it? and how much am i looking at? thanks again
Re: P0140 and P0325 (Gman8990)
if your not going to run 91 and your just buying the cheap stuff then you don't have to replace your KS.
02 sensor can be got from any kragen's or autozone...they are about 100 a piece and you need to know which o2 sensor it is.
02 sensor can be got from any kragen's or autozone...they are about 100 a piece and you need to know which o2 sensor it is.
Re: P0140 and P0325 (rxm6)
Personal experience, running the lowest octane will toss the CEL in about 2 days. I pick up a can of octane boost and keep things happy until the next fill up. Running the mid-grade will keep things in line and the high octane is just butter.....--Mike
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NutriaforBreakfast
- Posts: 1316
- Joined: Wed Sep 26, 2007 1:41 pm
- Car: Nissan Maxima 1995 VQDE engine
Re: P0140 and P0325 (Gman8990)
If your gas is too low on octane you can burn a hole in the top of your piston head. Any clanging you hear inyour engine upon acceleration is caused by "predetonation"which is very hard on your engine.
Your problem with the knock sensor could be related to your engine "jumping time". Please have the engine timingchecked. You can do this with a timing light. I am pretty sureyou cant change the timing if your Nissan Maxima is a 1995 orlater (thats when coils rather than a distributor was introduced)Certainly though Nissan can correct the timing? If your car wontstay timed then you probably have some worn parts (cranshaft, etc)lower end engine problems.
Your problem with the knock sensor could be related to your engine "jumping time". Please have the engine timingchecked. You can do this with a timing light. I am pretty sureyou cant change the timing if your Nissan Maxima is a 1995 orlater (thats when coils rather than a distributor was introduced)Certainly though Nissan can correct the timing? If your car wontstay timed then you probably have some worn parts (cranshaft, etc)lower end engine problems.
Re: P0140 and P0325 (NutriaforBreakfast)
True, however, Maxima's were designed with this in mind and thats why the KS was introduced. It allows any octane from 87 and up to be used so that no predetonation occurs regardless of the octane used. A bad or missing KS will always revert to a safe mode that gives low performance and low mpg, but will prevent knock.NutriaforBreakfast wrote:If your gas is too low on octane you can burn a hole in the top of your piston head. Any clanging you hear inyour engine upon acceleration is caused by "predetonation"which is very hard on your engine.
I could be wrong, but I think the only way timing is affected in the Maxima's is if the chain or sprockets fail since the timing is controlled electronically. Also, if the engine were jumping time you would get a different sensor going off. Can't think of the name of it, but its right there on your timing chain cover.NutriaforBreakfast wrote:Your problem with the knock sensor could be related to your engine "jumping time". Please have the engine timingchecked. You can do this with a timing light. I am pretty sureyou cant change the timing if your Nissan Maxima is a 1995 orlater (thats when coils rather than a distributor was introduced)Certainly though Nissan can correct the timing? If your car wontstay timed then you probably have some worn parts (cranshaft, etc)lower end engine problems.
Modified by rxm6 at 12:01 PM 4/23/2008
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NutriaforBreakfast
- Posts: 1316
- Joined: Wed Sep 26, 2007 1:41 pm
- Car: Nissan Maxima 1995 VQDE engine
Re: P0140 and P0325 (rxm6)
Maybe crankshaft position sensor or camshaft position sensor?
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allensteiner
- Posts: 1193
- Joined: Mon Oct 22, 2007 2:55 pm
- Car: 1995 Nissan Maxima GLE, 2005 Pontiac Bonneville SE
Re: P0140 and P0325 (Gman8990)
dude...don't be a cheap *** when it comes to fuel. once you start running premium you'll see a diference. i live in MT and all we have is crappy 91 premium but idaho has 94 octane gas so when i go over there - i'm a trucker - i always take a gas can with me - price the same as MT 91oct!!!Gman8990 wrote:There is no way im paying that much money for gas... how much is a KS gonna run me? and where is it?? also, the O2 sensor... where is it? and how much am i looking at? thanks again
when i lived back in Poland the lowest grade was 94 and you could get "premium" rated at 100 oct - something people call racing fuel?
anyways...the lower the octane count the ****tier the cars performance