Knock sensor+oxygen sensor codes:

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98_Q45
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So I been chasing down an issue way since last year. Originally thought oxygen sensors were causing an issue with the engine intermittently struggling to accelerate. It initially showed 2 of the lower ones. Changed those (albeit the originals were chopped as to indicate they were changed before) check engine light still didn’t go off. Found a blown fuse but then after I fixed it said no activity. CEL never went away. Intermittent hesitation seemed to had been cured with gas tank water remover and other additives every so often.

Fast forward a year: now the issue has become nearly a daily occurrence. It has now progressed to happening during highway driving as well. Press the gas, it just loses more power. Then it’ll magically fix itself. For a few miles, or a few days, then do it again. Usually when it behaves that way, the temperature gauge starts moving past half if I’m blasting the a/c or got off highway. A couple times it’s been really bad: almost flooring it, and it would only move 5 mph before backfiring and lunging forward.

Question is: do I want to do this Bank 1 knock sensor code issue? I need to hopefully fish it out by simply removing only the upper intake manifold. Don’t want to bother doing the lowers. Hell: I’d almost rather remove the alternator to reach it if I need to. Could this be something else besides knock sensor and oxygen sensor? Everything imaginable has been done.

I have P0134 P0158, P0141, P01459 for oxygen codes. Normally I only have 2 oxygen sensor codes. Sometimes it throws more than that.

P0325 knock sensor code.


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VStar650CL
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The knock code won't even turn on the MIL and it's very unlikely it's causing your issue. The major causes of P0138/P0158 are exhaust leaks or malfunctioning sensor heaters. P0141 indicates the left bank rear heater is inop, and with a previous blown fuse, I'd say it's possible you have some wiring damage down there. BUT (big but), nothing about the rear O2's is used to run the engine. They're strictly there to monitor the cats and can't cause the sort of performance issues you describe. With rear codes in the system the ECM won't be monitoring, so you won't be getting P0420/P0430 to warn you if your cats have gone south. Clogging cats can cause those sorts of symptoms. The P0134 is also a different story, that's for the left bank front O2. The fronts are used to run the engine, so if that sensor is producing data that confuses the ECM, all sorts of performance problems could result.

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VStar650CL
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PS - There's also a bulletin for P0138/P0139/P0140/P0158/P0159/P0160 for an ECM repro, ITB02-008. I doubt that's your issue all by itself, but if you have dated ECM software it certainly won't be helping matters. These are the old/dated ECM part numbers:
23710-3H000, -3H001, -3H005, -3H006, -3H007

98_Q45
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VStar650CL wrote:
Sat Aug 27, 2022 4:51 am
The knock code won't even turn on the MIL and it's very unlikely it's causing your issue. The major causes of P0138/P0158 are exhaust leaks or malfunctioning sensor heaters. P0141 indicates the left bank rear heater is inop, and with a previous blown fuse, I'd say it's possible you have some wiring damage down there. BUT (big but), nothing about the rear O2's is used to run the engine. They're strictly there to monitor the cats and can't cause the sort of performance issues you describe. With rear codes in the system the ECM won't be monitoring, so you won't be getting P0420/P0430 to warn you if your cats have gone south. Clogging cats can cause those sorts of symptoms. The P0134 is also a different story, that's for the left bank front O2. The fronts are used to run the engine, so if that sensor is producing data that confuses the ECM, all sorts of performance problems could result.
This is what I was wondering. Normally the front o2 sensor code has not come up. If I clear the codes, drive around and recheck it: generally just those 2 rears show up. Disappointing because I paid a (albeit small) shop to replace and I was standing right there. New sensor and then re-wired/shrink wrapped everything. After all that, showed no activity. I found the blown fuse “after” I had that done. Idk if that woulda solved it because I actually did re-do 1 of the oxygen sensor wiring my self prior to that.

But you’re saying it could be an o2 sensor or catalytic going bad, and don’t bother with knock sensor and knock sensor wouldn’t do that at all?? Also I had a knock sensor code on my 97 Maxima, I finally changed it, and the code went away. But it wasn’t lagging as much.

I also tried running only 91 gas in the past couple days. It seems to help keep the problem under control, and the other day I drove 170 miles highway no problem. But then yesterday it started doing it again out of nowhere. Always seems to happen once engine fully warms up. if that’s any clue.

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VStar650CL
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The knocks throw codes but don't really affect performance. Lots of people with older rides drive around with KS codes and don't even know they're there, and on models older than '09 I've seen KS's pop up right after installing brand new ones. The front O2 is a different matter. Even if it's come-and-go, it's telling you something isn't good in the left bank. I'd suspect the front O2 itself or the wiring. Narrow band O2's with a cracked ceramic substrate can work intermittently and be very hard to diagnose, because they basically act like a wiring problem. So I think I'd try changing one or both (at least the left bank) before anything else.

98_Q45
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VStar650CL wrote:
Sat Aug 27, 2022 8:58 am
The knocks throw codes but don't really affect performance. Lots of people with older rides drive around with KS codes and don't even know they're there, and on models older than '09 I've seen KS's pop up right after installing brand new ones. The front O2 is a different matter. Even if it's come-and-go, it's telling you something isn't good in the left bank. I'd suspect the front O2 itself or the wiring. Narrow band O2's with a cracked ceramic substrate can work intermittently and be very hard to diagnose, because they basically act like a wiring problem. So I think I'd try changing one or both (at least the left bank) before anything else.

Okay, I’ll go the front o2 route. I was trying to do this last year, but I kept getting the run around trying to find a place to do it (come back next week, they probably won’t come out, etc). Mysteriously, the issue went away for awhile and would only pop up every so often.

However, I have noticed: it often “goes away” after shutting off the engine. I just drove 170 miles highway today. It was initially really boggy, practically slowing down whenever I would try to speed up. When I turned it off and restarted it halfway thru the drive, acceleration was back to normal.

But at this point it’s happening too often to not figure out ASAP. Much rather do o2 than knock sensor though.

fontana dan
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Have you looked at OBDII live data while the issue is occurring? It will help you solve it if you understand what is going on with the engine while it is bogging down.
You said someone has chopped up the wires on the O2s already? I would look there very closely for damage to the circuit.

98_Q45
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fontana dan wrote:
Tue Aug 30, 2022 9:44 pm
Have you looked at OBDII live data while the issue is occurring? It will help you solve it if you understand what is going on with the engine while it is bogging down.
You said someone has chopped up the wires on the O2s already? I would look there very closely for damage to the circuit.
I haven’t, but good point. I have the Bluetooth thing that connects to my phone, but it’s pretty detailed.

I have looked at the rear o2 sensors and it shows nothing but a flat line. Like dead, dead (mind you I had them replaced new last year, and the wiring re-cut and wrapped). Idk if they’re just not getting signal from the cat or what. I’ve seen articles saying maybe not enough heat reaching or whatever.

I’m likely just going to take it to a nearby exhaust shop and replace the 2 upper ones. And going to tell them I need that CEL to go off because that’s the only 2 things causing it. I have fixed and cleared every single other code including the emissions and purge lines.

fontana dan
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What voltage are they reading while theyre unresponsive at "flat line"?
Take a look at your long term fuel trims B1 & B2, as well as all upstream and downstream O2 sensor readings while the engine is running.
If the fuse was blown for your O2 heater that points towards a short to ground- bad wiring. If the heater is not functioning you could have an unresponsive O2 sensor.
Replacing the upstream sensors is not likely to fix the problem with the downstreams.

98_Q45
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fontana dan wrote:
Tue Aug 30, 2022 11:13 pm
What voltage are they reading while theyre unresponsive at "flat line"?
Take a look at your long term fuel trims B1 & B2, as well as all upstream and downstream O2 sensor readings while the engine is running.
If the fuse was blown for your O2 heater that points towards a short to ground- bad wiring. If the heater is not functioning you could have an unresponsive O2 sensor.
Replacing the upstream sensors is not likely to fix the problem with the downstreams.
Just seeing this. I still haven’t had a moment to read up the readings.

However I had the front oxygen sensors replaced today, and still same s***. I’m quite annoyed at this point. I don’t even think that was the cause. I started to just schedule a straight diagnosis without buying anything but I was fairly certain that was contributing to the issue. Only setback is paying the shop to do them.

I think the next step is fuel pump and/or filter. It can’t be much more things than that. Just tired of chasing the issue down and not getting any solution.

fontana dan
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How does the car run at wide open throttle(WOT)? What is the reasoning for fuel pump/filter?
One of the first steps i do in diagnosing a car with an issue like this, is to floor it and watch live data to make sure both upstream o2 sensors go rich (.9v). That will quickly show if fuel system is able to supply the engine with enough fuel.
You've already identified a problem area in the o2 WIRING. You need to test the circuit.

98_Q45
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fontana dan wrote:
Sun Sep 11, 2022 8:11 pm
How does the car run at wide open throttle(WOT)? What is the reasoning for fuel pump/filter?
One of the first steps i do in diagnosing a car with an issue like this, is to floor it and watch live data to make sure both upstream o2 sensors go rich (.9v). That will quickly show if fuel system is able to supply the engine with enough fuel.
You've already identified a problem area in the o2 WIRING. You need to test the circuit.
At wide open throttle, it’ll rev upwards to 5,600 (had to do this the other day to pass some idiot who cut me off)…but it’ll barely pick up much speed for a few seconds until it gets enough kick. It’s also “revving” on cruise control for the smallest of highway hills like I’m driving a Corolla. So I’ve been careful not to pull out into traffic unless there’s no cars nearby, because I won’t have enough speed to accelerate.

I get lots of squiggly lines on my front O2 sensors, but just a flat line on 1 rear sensor and no activity on the other. I’m going to check around with the wiring on bank 1 again because so far after fixing the front o2, that’s the only one showing code now. I feel the knock sensor is being triggered by the lack of power

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VStar650CL
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That sounds like an engine that can't breathe. With your rear O2's out of commission, might be worth throwing a vacuum gauge on it to see if you have a clogged cat. Should run 18~20 inches at idle, if it drops precipitously when you gradually roll the throttle on with no load, the exhaust is blocked.

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VStar650CL wrote:
Mon Sep 12, 2022 11:41 am
That sounds like an engine that can't breathe. With your rear O2's out of commission, might be worth throwing a vacuum gauge on it to see if you have a clogged cat. Should run 18~20 inches at idle, if it drops precipitously when you gradually roll the throttle on with no load, the exhaust is blocked.
I asked the shop who put the o2 sensors in, he didn’t seem to think it would be necessary considering it still can drive long distance, and it’s not stalling out or anything. It’s just intermittently not getting power when pulling away from a stop, but then after a few seconds it’ll lunge into speed. However it’s now progressed to difficulty maintaining on highway here and there. It’ll cruise okay, but give it throttle, and it’s like trying to floor a semi lol.

Fuel pump is on the way. The only other thing that could be suspect is any of the 4? Fuel dampers/regulators. But I replaced 2 previously, the one that was faulty leaked at the vacuum but didn’t give performance issues except hard start. But there’s one on the fuel rail under intake? It’s discontinued and out of stock. I’m hoping and crossing it not that. But so far everything seems to point to slowly dying fuel pump.

I have however poured a 2nd bottle of “catalytic converter cleaner” into the tank just to rule anything out. Hopefully it should be squeaky clean at this point.

98_Q45
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Well this is just depressing…

Did the fuel pump, not hard but not fun either. Started right up, and drove off fine. But it always seems that as soon as it gets up to operating temp for a couple minutes, it goes right back to dragging like I’m towing something.

At this point everything works. Not trying to lose hope. But maybe you are right about the catalytic converter. I’m trying to self diagnose reading articles about symptoms and causes. Oxygen sensor and fuel pump seemed to check all the boxes. But alas, the issue persists.

Likely have to run it back to the muffler man and get him to figure this out deeper. And why is the issue so intermittent? Last year I had this problem, was running all over town to figure it out: finally just did some water remover in the tank and issue cleared up and I drove to Arizona with no problems. And did multiple other drives since, some that involved steep mountain grades, and pulled fine with trunk full of luggage.

It’s only recently that it’s become persistently bad, maybe I try to add another 2 bottles of water remover but idk if that’s going to do the trick. Also seemed to only do it when low on fuel. But lately it’s doing anytime after warmup. And only after warmup and especially with a/c on.

fontana dan
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If your front o2s are functioning then I would think the car should run ok. However I've heard of Nissans doing weird things when the rear o2s aren't working. Remember even if the sensors themselves are good, they are useless if the wires between them and the engine computer are damaged.
You still have 3 trouble codes stored. O2 heaters are important. The circuit is clearly damaged.
It could be the car is lagging after it goes into closed loop fueling, due to the o2 sensor issues. You need to get those codes sorted out. Key on engine off you should have voltage(5 or 12v?) for the heater at the o2 electrical connector.
Remember to keep it simple...and do not even think about replacing those catalytic converters.

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VStar650CL
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fontana dan wrote:
Thu Sep 15, 2022 10:04 am
If your front o2s are functioning then I would think the car should run ok. However I've heard of Nissans doing weird things when the rear o2s aren't working.
I dunno, but I don't think it's a failsafe behavior. On late '90's stuff there were only a few DTC's that would trigger an ECM failsafe (in this case P0100, P0115 and P0120), and none of those are for the exhaust sensors. See EC-88 (pdf page 90):
https://www.nicoclub.com/service-manual ... 8%2Fec.pdf

fontana dan
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VStar650CL wrote:
Thu Sep 15, 2022 11:32 am
fontana dan wrote:
Thu Sep 15, 2022 10:04 am
If your front o2s are functioning then I would think the car should run ok. However I've heard of Nissans doing weird things when the rear o2s aren't working.
I dunno, but I don't think it's a failsafe behavior. On late '90's stuff there were only a few DTC's that would trigger an ECM failsafe (in this case P0100, P0115 and P0120), and none of those are for the exhaust sensors. See EC-88 (pdf page 90):
https://www.nicoclub.com/service-manual ... 8%2Fec.pdf
I'm just proposing the possibility that the dead exhaust sensor could be causing the ECM to do something weird with fueling. Good thinking though; if not an o2 issue I would bet the problem with this car lies with one of the sensors listed on EC-88.
It would be very helpful to know the fuel trim values as well as what the O2s, MAF, crank position, and TP sensors are reading while his '98 Q45 is bogging down. Live OBDII data is your friend when diagnosing drivability issues.
This is an example of a downstream o2 causing fueling issues on a (much newer) 2011 frontier. Might not be applicable seeing as this truck uses A/F sensors upstream. Watch around the 13:00 minute mark to see how he tests the oxygen sensors.

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fontana dan wrote:
Thu Sep 15, 2022 10:04 am
Remember to keep it simple...and do not even think about replacing those catalytic converters.
Lol no worries there, I can’t even afford that right now anyway.

But I had an idea earlier and think you also hit on it. I think the actual issue might just be: THE TPS! Now, that’s just a very brief assumption, but if I’m right (and read a couple articles regarding it), then this will be the 3rd time I’ve had TPS issues on a vehicle this year. I have 2 other vehicles where the throttle would intermittently get “stuck” and I could shift into neutral: and the RPMs would stay up to 2-2,500 until shut off for a couple minutes. On one vehicle, it was so bad that I had to disconnect the battery because it started acting up while the mechanic was diagnosing it. It would still do it here and there, forcing me to shift into neutral and shut off the engine. They basically would cruise down the highway on their own, with me barely tapping the gas. And would seem to stay at 70 mph RPMs when I tried to come to a stop.

I’m still going to recheck the oxygen sensor wiring, but this TPS isn’t throwing a code though (seems like they never do). However, I have at least a couple of times started the car and the traction/Slip light comes on, WHICH…ironically comes on when the TPS is disconnected when adjusting idle.

So, I’m thinking of throwing 1 more part at it…maybe even cleaning the TPS and see what happens. It’s happening far too sporadic to be something static like a clog. And it’ll seem to coast on the highway fine until I press the gas, then it just bogs down. And today I drove 200 miles, it did okay but wasn’t willing to accelerate eagerly.

Also: this issue been happening before I did anything to fix the rear oxygen sensors. For the longest time, one had a broken wire (previous owners must had tried to replace to pass California emissions, ended up just maiming the wires instead of using a direct fit) and both had a burned out fuse. Never realized it until this issue started happening last year.

98_Q45
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Ugh, the disbelief continues:

Changed the TPS (seems like there’s actually 2, but only one that I suspected would have been faulty).Issue STILL persists!

Immediately after the fix it seemed to be resolved. The “stall” seems to happen very sporadically and after several minutes of warm up. I am just exhausted.

It also does not happen all the time. It’ll be riding fine, and then I come to a stop light. Hit the gas and feels like I’m towing 1,000,000 pounds. Rpm won’t move past 1,000/1,500, then after a few seconds it’ll clear up and rpm will surge to 2,000 ish or however far down I have the pedal.

When it does it on the highway, my fuel mileage drops drastically and if I’m trying to go uphill with a/c on, the temperature gauge will start moving past half. But regardless of when it happens, it’ll “fix itself” and then malfunction just at random, often multiple times per commute.

I am now thinking someone may be right about the catalytic converter. I have a shop diagnostic tomorrow, hopefully I’ll get some answers. But idk because I also have another vehicle that broke down so money is sparse.

Hate to be a complainer but man: times like this really zap DIY confidence, and the money I’m spending wouldn’t be so bad if it weren’t for my work being very impacted by the sluggish economy. God help me…

Also I’ve charted live data: rear oxygen sensors are showing only 1 bank has a single line of voltage. The other has 0 voltage. Keep getting codes for high voltage on the working one. I’ll clear it, then it’ll come back on soon as I turn on the engine. Idk why the other one isn’t showing any voltage and the other is just a flat line of like 1.7 volts I believe.

fontana dan
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If you want to fix this problem you need to use a scan tool or pay someone who has one. I would say next to test the maf sensor.
Unload the parts cannon. Test, don't guess.

MowgliCSM
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I had similar issues with my S-Class. Both upstream o2 heater circuits failed at the same time (huge clue). Pinned my FT to +30%. Fouled the o2's so they wouldn't work anyway. So I disconnected all the o2's and scoped a wire going to the alternator to find no square wave, so the Lin-Bus was dead. Sent the ECM out and they confirmed a damaged processor. Replaced ECM, upstream o2's and plugs, all good. You need to stop throwing parts at it like Dan said. My Benz is more complex than my Q45, but the same approach should be utilized. There are ways to eliminate parts without replacing them. You need a decent scan tool or find someone with one. At a minimum get a Nissan Consult interface and hook it up to a laptop. It's pretty cheap. Live data is super useful.

98_Q45
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Okay, didn’t think I would be saying this so soon BUT…I believe the issue has actually been resolved with replacing the throttle position sensor. I think initially, the computer probably didn’t recognize I put a new one in, and still gave me some hesitation.

I just did a 350+ mile drive, and my gas mileage seems to finally be back to what it should be (excess fuel waste has been an annoying add on to this). I usually should be able to get about 120-140 miles (depends how full the tank and how fast driving and a/c use) by the time I hit 3/4 tank. Before…I was hitting 3/4 tank after only going 70-80 miles!

Even held up going on a steep incline on the highway, no issues. I just hope hope this continues and doesn’t come back. However, considering how often it was happening…I’m pretty confident the issue has been resolved.

I’m still down to 1 post cat oxygen sensor with no voltage, however. But I think there may be a wire that wasn’t matched right. I do however have a good little Bluetooth scanner that reads codes, but I never got anything about TPS sensor. I had to Google that one a bit.

I also didn’t realize the TPS is what controls all throttle movement. So my conclusion was it was getting some faulty signal and not opening the throttle properly. But I never noticed any pattern because it would happen so randomly.

Reminds me of my Maxima that developed a bad intermittent stall out problem last year. Took it to 3 shops including Nissan, couldn’t get it resolved. Finally threw in a $50 ebay MAF, and it cured it.

At least now: I have a bunch of new parts that needed changing anyway eventually lol. Even though I wasn’t happy about changing the fuel pump unnecessarily. But I was desperate. I believe it was the original Japan brand.

98_Q45
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Update: decided to throw in a new fuel filter because the issue snuck up on me 1 time during stop and go traffic.

But since then, all been well. Hoping it doesn’t come back again lol.


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