Few codes... need help asap before SMOG test.. - Nissan Murano Forum
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post #1 of 13 Old 06-03-2019, 06:26 AM Thread Starter
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Few codes... need help asap before SMOG test..

I have a CEL that usually stays on.. but does at times turn off before coming back up. I had the codes read and get 3 at the moment...


P0300 - this has been an on/off issue for a while. No noticeable misfiring or engine stuttering.

I also have a P1273 and P0455 at the moment.

Where could I start to get rid of these(?).. before my SMOG, which is due within two weeks. I would like to keep this car running on the road, since I have no other issues other than this CEL. As I mentioned, the CEL does turn off at times but stays off only about 30-100 miles. Any help would be great. Thanks!!!
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post #2 of 13 Old 06-03-2019, 10:46 AM
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I have a CEL that usually stays on.. but does at times turn off before coming back up. I had the codes read and get 3 at the moment...

P0300 - this has been an on/off issue for a while. No noticeable misfiring or engine stuttering.

I also have a P1273 and P0455 at the moment.

Where could I start to get rid of these(?).. before my SMOG, which is due within two weeks. I would like to keep this car running on the road, since I have no other issues other than this CEL. As I mentioned, the CEL does turn off at times but stays off only about 30-100 miles. Any help would be great. Thanks!!!
The code descriptions for reference:

P0300 - Random Misfire
P0455 - Evaporative emission (EVAP) system -large leak detected
P1273 - NISSAN - Air Fuel Ratio Sensor 1 Bank 1 Lean Shift Monitoring

Looking at those codes collectively, it looks like the engine is running abnormally lean--possibly a vacuum leak? An excessively lean condition can cause random misfires. With engine running at idle, take a look at long-term fuel trims for both cylinder banks with a scan tool and see if they're high. If they are high, increase engine speed slowly up to 2,500 RPMs and see if the fuel trims start to come down--if so, then you've got a vacuum leak (...in that case the EVAP code might be a clue here such as a purge control valve stuck open).

BTW...what year is your Murano and how many miles on the engine?
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post #3 of 13 Old 06-03-2019, 05:49 PM Thread Starter
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Thank you for the feedback! That is some great info. I will check several areas like the intake and other hoses for vacuum leaks. The car is an 04í w/ a whopping 256k miles and running strong... other than a visible CEL.

Otherwise, I hope itís not the intake manifold leaking(?) I did do the spark plugs and removed the plenum twice (reusing the same ďnewĒ gasket the second time), so I hope thatís not leaking air. I also replaced the rear air fuel sensor w/ an eBay sensor when I had the intake mani out because it took 2 minutes to replace over. Itís the one that sits up top, near firewall and hard to get to unless the intake mani is out. Canít remember if thatís B1S1? It fixed a previous CEL when I put that sensor in... but I wouldnít be surprised if that sensor failed, since it was a cheap eBay part. Or is B1S1 located elsewhere?

As I mentioned, the code does turn off from time to time but I cannot get it to stay off for more than about 30 miles usually. (Plus I donít think itís actually cleared from the system when itís ďOFFĒ).
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post #4 of 13 Old 06-03-2019, 06:51 PM
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Thank you for the feedback! That is some great info. I will check several areas like the intake and other hoses for vacuum leaks. The car is an 04í w/ a whopping 256k miles and running strong... other than a visible CEL.

Otherwise, I hope itís not the intake manifold leaking(?) I did do the spark plugs and removed the plenum twice (reusing the same ďnewĒ gasket the second time), so I hope thatís not leaking air. I also replaced the rear air fuel sensor w/ an eBay sensor when I had the intake mani out because it took 2 minutes to replace over. Itís the one that sits up top, near firewall and hard to get to unless the intake mani is out. Canít remember if thatís B1S1? It fixed a previous CEL when I put that sensor in... but I wouldnít be surprised if that sensor failed, since it was a cheap eBay part. Or is B1S1 located elsewhere?

As I mentioned, the code does turn off from time to time but I cannot get it to stay off for more than about 30 miles usually. (Plus I donít think itís actually cleared from the system when itís ďOFFĒ).
If the problem started soon after you changed the spark plugs then it could be the intake plenum gasket isn't seated properly. B1S1 is the O2 sensor right before the catalytic converter. Yeah, cheap parts sometimes don't last long. You can watch the O2 sensor voltages with a scan tool as well to see if they don't look right (...use a graphing mode).
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post #5 of 13 Old 06-03-2019, 10:38 PM Thread Starter
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Looking into it some more.. could the cause potentially be a bad evap purge valve causing the large “leak” allowing the sensor to read the lean amount? Still not sure about the P1273 or the exact cause of the P0300 but looking online and the P0455, it seems to be a common problem with the evap purge valve staying stuck open....
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post #6 of 13 Old 06-03-2019, 11:44 PM
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Looking into it some more.. could the cause potentially be a bad evap purge valve causing the large “leak” allowing the sensor to read the lean amount? Still not sure about the P1273 or the exact cause of the P0300 but looking online and the P0455, it seems to be a common problem with the evap purge valve staying stuck open....
It could be. Very easy to test if it's stuck open. Simply disconnect the tube from the back of the purge control valve (i.e. the tube that runs to the EVAP charcoal canister near the fuel tank) and also disconnect the electrical connector to the purge control valve. Start the engine and feel the opening on the back of the purge control valve where you removed the hose--you should feel no vacuum. The reason you should feel no vacuum is that the valve should always be in the closed position until commanded open by the PCM, which is not possible since you removed the wiring harness connector. Keep in mind that this might set a code because the connector was removed while the engine is running--you can just clear it with a scan tool.

Another option if you have a vacuum pump is to disconnect the hose from the intake manifold that runs to the front of the purge control valve and hook up the vacuum pump and draw a vacuum (about 15 in/hg) while the engine is OFF. If the purge control valve is working properly, it should be closed and hold a vacuum. The latter test will not set a code, but remember to put the hose back on to the intake manifold when finished.
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post #7 of 13 Old 06-04-2019, 02:03 AM Thread Starter
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I will look more into the car tomorrow. Iíll check the intake and other hoses for cracks, etc.

Otherwise, I manually reset the CEL in the car today and drove it to Autozone. The CEL was off on the way there BUT for so reason it would come on/off every minute or so very quickly... it was easy to miss at times. Once I turned the car off and restarted it, the CEL was back on.

I checked for codes and I now only have the P0300 and P0455 after the reset.... still leading me to believe that the evap purge valve may be at fault. Seems like a common Nissan issue. Iíll test it more tomorrow as you mentioned and I may connect the terminals to +/- to see if the solenoid opens properly (seen it tested by someone on YouTube, so Iíll pull it out and give it a shot). The P0300 still baffles me. Thatís been on/off for a while now and canít pinpoint the cause.
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post #8 of 13 Old 06-04-2019, 10:36 PM Thread Starter
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Quick update:

Today, I decided to take a quick look at the murano. I started off by unplugging the battery. I then checked the air filter, cleaned MAF sensor w/ specific cleaner and made sure to tighten down the intake and check surrounding hoses for cracks, holes, etc.

Secondly, I decided to replace the front 3 spark plugs with a used low mileage set I had in the garage (factory NGKs). Made sure to regap all 3 to .044. Otherwise, I didn’t see anything else that I could get to easily (like the rear 3 plugs).

Lastly, I ended up removing the EVAP Purge Valve from the rear undercarriage and hooked two wires up to the +/- terminals onto the battery. I was looking to see if the solenoid/spring inside would actuate (seen this done on YouTube). Not sure if that is the best way to check but either way, I noticed a very slight click inside the valve and the solenoid/spring to appear stuck open. This leads me to believe that the P0455 may be caused due to the valve being stuck open.. but I’m not sure. Anyways, I plugged it back into the car and reconnected the battery.

So far, no CEL. I managed to start the car on/off about 6 times within a short 5 mile drive, but at least the CEL managed to stay off this whole time. I will see what happens in the next couple of days. Not sure if me pulling and messing with the EVAP purge valve caused the CEL to shut off.... I may order a new EVAP valve and just replace it anyways, as I continue driving and monitoring the vehicle.
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post #9 of 13 Old 06-12-2019, 06:49 PM Thread Starter
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So the CEL was off for about 150 miles last week. I wanted to get the SMOG test done but they said that the CAT was “not ready” and although there were no codes, the system wouldn’t let it pass. They stated there was a B1S1 sensor was not ready and the CAT not getting hot enough...

Suggestion/possible sysmpton was that my thermostat may be stuck slightly open and not allowing the CAT to heat up properly???.. any takes on that? Otherwise I assume this may have also caused a bad reading on the O2 sensor? No codes for sensor though.

I do have a spacer on my downstream sensor that prevented a previous P0420 code, would this maybe cause the reading to show that it’s not heating up properly and causing it to be “not ready?” That sensor was the downstream side, so I believe that it was B1S2 where the spacer is.

On the other hand, I randomly get a P0300 and P0302 pop up. Either way, after about 180 miles the CEL is back up. Haven’t checked but I assume it’s the p0300 up again. Now I’m completely confused as where to start. Car acts and drives completely fine otherwise.
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post #10 of 13 Old 06-12-2019, 08:31 PM
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150 miles should be more than enough time to allow your OBDII monitors to be ready. What scanner do you have, BTW? Any decent scanner can usually check the readiness of the OBDII monitors so you know your car is ready for inspection before you go. Check the O2 sensor monitor in mode $06 with your scanner and see if the readings are out of spec. Watch the voltages on live data. You said you replaced that O2 sensor with a cheap eBay part so maybe it's not working properly.

The line about the thermostat and the cat makes no sense--coolant doesn't run through your catalytic converters. A catalytic converter gets hot because of the exhaust running through it and the chemical reactions that take place as the exhaust interacts with the catalyst substrate. The exhaust coming out of the back of the cat is hotter than the exhaust coming in precisely because of those chemical reactions. If you have a spacer on your downstream O2 sensor, it's "preventing" the P0420 code because it's hiding that you have a bad cat. That's why people install O2 sensor spacers (...tuners also use them to hide that they've removed all the substrate from their cats to reduce exhaust backflow). When the substrate in the cat goes bad, it won't "heat up" because the substrate is no longer chemically interacting with the exhaust gases.

Where to start? Start by getting the code and posting what it is along with the freeze frame data that was stored when the code was triggered.
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post #11 of 13 Old 06-13-2019, 05:59 AM Thread Starter
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The scanner I have is cheap and does not show live data, to be honest, I think my scanner is faulty now as well.

As far as the readings I got, I ended up cheaxking this at 3 different smog locations (not doing the actual test).. just had them use their readers. First two uses nicer scanners and said no CEL codes but the CAT was not ready. The third place also said not ready but then that scanner was showing up the P0300 and P03002 codes. Also a cheaper scanner and the same as Autozone. Weird thing is that only the cheaper scanners came up with there codes... the actual SMOG spot said no to any codes other than the CAT not being ready.

When I did have the CEL off and 150 miles on the car, the couple of SMOG places told me to drive it at 50-55 mph for 10 minutes to get that CAT ready. They were very specific on that speed and keeping it on the throttle for the full 10 minutes. Maybe I should reset it again, attempt to get no code and drive as they said to hopefully get that CAT ready.

Iím really not sure what else to do. ďI need coffeeĒ and as you mentioned everything in your last post, I completely agree with everything that youíve said. I donít see the thermostat being an issue but what they were trying to say is that maybe itís running my engine cooler and not allowing to allow the CAT to warm up fully. Guy told me that the CAT reading was at 89 Celsius and should be around 95 Celsius before the CAT/computer could get a proper reading.

Otherwise, I think the whole system is out of whack. At one time it shows me these misfire codes, then it doesnít. Before the code went off I also had a P0455 and now nothing... I understand that there is a problem somewhere but I donít fully believe that all of it is 100% accurate. I believe that one thing is triggering another without a definite cause coming up from one single issue. Itís kind of like a domino affect.

I donít know where else to look and I DO NOT want to replace parts without knowing EXACTLY where the problem sits. Iím not going to replace the cylinder 2 injector... even though I changed that spark plug and moved the coil between cylinder 2 & 4. The p0300 and P0302 still comes up.. basically now leading me to believe that the injector would be at fault(?) Then at other times there is no issue..
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post #12 of 13 Old 06-13-2019, 08:24 AM
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After reading thru this thread several times, it seems that everything started with the P420 code. Replacing the Oxysensor didn't resolve the issue so you added the spacer to get rid of the code.

With as many miles on the car, I strongly suspect that you have a bad rear cat, unless it's been changed. A plugged cat will not heat up in the same manner as a properly functioning cat. If this is the case, you can play to dooms day with everything else, you will not pass emissions testing.

JM2C from what I've read.

Have a good day.
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post #13 of 13 Old 06-13-2019, 10:04 AM
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srT4URBO,

First, I'm looking at your previous threads and it's now apparent that this is an annual issue. It seems the last couple of years around the same time, you start a new thread about random misfires, misc. codes etc. and you need to get a smog test soon. You really should include all the prior history when you ask for help (or revive your old threads).

Second, if you're serious about fixing car problems yourself then you need to invest in a good scanner. A decent scanner is not that expensive and is invaluable for troubleshooting DTCs. If you're still in CA, go to Harbor Freight and buy one of their Zurich scanners--they have one for $90 that looks to be good enough although their more expensive options can do more (e.g. clear SRS codes). You might even be able to use one of their 20% off coupons.

Finally, at 15 years and nearly 260k miles, your car is not long for this earth. When cars have intermittent "MIL goes on/off periodically" problems, there is often a window between when all the emissions system monitors are ready and when the problem "acts up" triggering a code. What some people do is locate an inspection station that's not too busy, clear all the codes in the PCM with their scanner and then drive around watching each of the I/M monitors until they all read as "ready" then drive right to the inspection station for their smog test. After getting their sticker, the MIL usually lights up as they're pulling out of the parking lot.

Good luck!
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