NP300 D23 YD25DDTI Going Into Limp Mode

[thathawkeye06]

Hi, Josh here i got a 2020 NP300 D23 with the YD25DDTI engine and i’m pretty confused on what is happening with my truck right now. It’s going into limp mode but i cannot determine why, the problem is it does not want to rev past 2,500 RPM’s and can get up to 3,000 RPM’s but i gotta force it like going downhill on first gear for example, mine is a 6 Speed Manual btw, i’ve cleaned the MAF, changed the MAP for a brand new oem one, changed the intercooler piping and cleaned the intercooler, lubricated the vgt actuator, cleaned the SCV, no boost leaks, the only thing i noticed that i think is not normal was that my fuel pressure got up to 192 MPA at WOT but other than that nothing, in my country the YD25DDTI comes with no EGR so the problem is not that, and i did a DPF delete.

I’ve tried resetting the ecu but this only fixes the trouble for a short time and then goes back to not revving past 2,500 RPM’s but last week i did this and the problem got away for a whole week but the truck is back on limp mode, the only code i got is a P0380 for the glow plugs but my truck starts right up and no rough idle and just a tiny small bit of white smoke when i turn it on in the morning and i guess that’s because of the DPF delete, anyone got any insights on a similar trouble going on.

Note to mention that the fuel rail pressure only goes up to a maximum of 90 MPA at WOT when it’s on limp mode. When it’s functioning as it should i got a maximum of 192 MPA.

 

[Old.Tony]

It could be the SCV, which produces a "limp mode" without codes or Check Engine Light. The SCV will either be dirty or damaged.

First step: put some GOOD injector cleaner in the tank. Liqui Moly Fuel System Treatment is my general go-to but you can use others, maybe Google up some reviews on ones you have locally.

If you can't get no satisfaction (apart from the record being upside down* ) you're probably going to have to replace the SCV.

In Australia, we can buy a new SCV from Nissan for around $240 or we can pick up a cheapy on eBay for around $40. The cheapies are ok probably 75% of the time. I don't know what your local Nissan dealer will try to steal from you for a new SCV.

 

[thathawkeye06]

It could be the SCV, which produces a "limp mode" without codes or Check Engine Light. The SCV will either be dirty or damaged.

First step: put some GOOD injector cleaner in the tank. Liqui Moly Fuel System Treatment is my general go-to but you can use others, maybe Google up some reviews on ones you have locally.

If you can't get no satisfaction (apart from the record being upside down* ) you're probably going to have to replace the SCV.

In Australia, we can buy a new SCV from Nissan for around $240 or we can pick up a cheapy on eBay for around $40. The cheapies are ok probably 75% of the time. I don't know what your local Nissan dealer will try to steal from you for a new SCV.

Thanks for the reply, i’ve tried anything even cleaning the SCV and no luck, but tomorrow a friend of mine who sells nav parts will send me a good one tomorrow to test and see if the problem still keeps happening i’ll keep you informed on how it turns out.

 

[bshrngr]

Thanks for the reply, i’ve tried anything even cleaning the SCV and no luck, but tomorrow a friend of mine who sells nav parts will send me a good one tomorrow to test and see if the problem still keeps happening i’ll keep you informed on how it turns out.

The cheap Ebay SCV's problem is that the paint flakes of the return spring and jams the SCV causing all the usual SCV faults even when its new ... If you take it off and clean the spring in thinners they works just as well as any other ... The other problem when that happens is the ECU learns bad values and the reset only works once the engine is hot ... So then the ECU can't control the fuel pressure like it should when cold and it limps out ... Not sure if it's a coolant temp or fuel temp (or both) threshold it's looking for but it won't reset when cold even though the scan tools say it's completed ... I learned this the hard way !!! ...

 

[bshrngr]

Just another insight, 90mpa is the default value in the ECU. If you disconnect the fuel pressure sensor this is what it reads till you cycle the key regardless of wether you reconnect it again ... it might be an intermittant wiring or connector problem thats causing it to loose the sensor but that usualy raises a pressure sensor code ... something to look into anyway ...

 

[thathawkeye06]

Thank you all for the insights, apparently it was the scv that was faulty even tho i’ve cleaned it cause i’ve switched it today for a good one and the problem stopped, tested the truck under conditions that the limp mode appeared before and the truck pulled like a train. Problem Solved.

 

[thathawkeye06]

Nevermind… it was pulling like a train for a while but now the problem has comeback. At this point i don’t know what else to look up for…

 

[Old.Tony]

Nevermind… it was pulling like a train for a while but now the problem has comeback. At this point i don’t know what else to look up for…

Another thing that causes odd limp modes without a light is the turbocharger overboosting. You could ask your ECU what kind of boost level it's getting. Torque (Android app) can graph this for you, and you can see the results in a spreadsheet. Watch for when the boost heads over 23/24psi, mine would go straight into limp mode when that happened. I've currently got my boost set to peak around 21psi (and now and again I'll see it hit 22psi).

 

[thathawkeye06]

I cannot believe what the problem turned out to be, it was some headlights i’ve installed, when the headlights are turned on the truck goes into limp mode automatically and when i turn them back off the limp mode goes away just as i turn them off. Do any of you heard about anything about something like this, and in that case what type of leds can i install that does not make this issue.

 

[Old.Tony]

That's a first for me. Never heard of that before.

How many watts were the globes?