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Nissan Altima SV 2019
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I have noticed RPM fluctuation while am cruising, it does not happen at low speeds, I tried to clean the fuel filter it disappeared for a while and came back again, I changed it but it keep happening.RPM problem this is a link for the video I hope it can help clarify it.
 

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2022 Altima SV
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I can't see it but you checked the fuel filter so I assume you checked the air filter and plugs as well, right? Did you run the scanner for any errors at all? if no errors show, could it be the slippage of the CVT belt? I'm not sure how you can scan this but I would think that's cause for the RPM spikes? see if that happens on certain RPM and to mimic the RPM at low speed to confirm CVT belt slip. Almost forgot, oxygen sensor? that would show on the scanner
 

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I have noticed RPM fluctuation while am cruising, it does not happen at low speeds, I tried to clean the fuel filter it disappeared for a while and came back again, I changed it but it keep happening.RPM problem this is a link for the video I hope it can help clarify it.
Are you aware that the fuel filter is part of the fuel pump that's inside the fuel tank? To check fuel flow, tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. The reading at idle should be 51 psi. There may be a problem with the CVT. To enhance longevity, the CVT fluid should always be replaced every 30,000 mi. When the fluid stays in too long, the chemical properties of the fluid get compromised and it can no longer provide that cushion that's so needed between the steel belt and the cones. Perform a simple drain/fill; it might fix your problem.

There are many conditions in the CVT that could cause it to drop into "fail safe mode". The Transmission Control Module (TCM) has a fail-safe mode. The mode functions so that operation can be continued even if the signal circuit of the main electronically controlled input/output parts is damaged. One of the first things to do is perform an ECU/TCM code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the Factory Service Manual (FSM) for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM from this web site: https://diyservicemanuals.com/nissan-altima-service-repair-manuals/. The section TM is the one you need to read.

To be able to read CVT codes, download a copy of the CVTz50 app for an android smartphone and get a VeePeak VP11 adaptor for your diag port (the VP11 is the cheapest ELM327 that works right with CVTz50, not all of them do). With that, you can read any CVT codes yourself, read the CVT temperature in realtime, and also check the CVT-A/CVT-B count for any history of overheating. If something bad did happen, at least you'll get an inkling of what it was from the past evidence by seeing that the counts are greater then zero.

If the CVT only goes into "fail safe mode" when fully warmed up, then the suspected failing component may possibly be the CVT temperature sensor circuitry; this is just a guess, so the code readout is essential. P17F0 and P17F1 never turn on the MIL on any Nissan model. P17F0 is the CVT "death code", it means severe belt slippage was detected. There are "judder detection" codes in almost everything 2013 and up that give a quick estimation of the CVT's condition and usually determine what fix is applied. P1F71 generally means a new Valve Body as long as a belt inspection doesn't reveal damage, P1F70 is a "death code" that almost always means belt damage and a rebuild or replacement. Minor slippage causing a P1F71 can often be resolved with timely fluid changes, but serious slippage with a P1F70 is usually a death warrant for the trans.
 
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