[Pvyton_]

So today while driving I got the dreaded "Service Engine Soon" light. I took it to the get the code ran and it was the "P0128" code.

I have a few questions surrounding this code. I recently upgraded my whole Radiator/Thermostat and cooling system in my 05 Xterra to this kit . It's a complete overhaul of the cooling system, the thermostat even opens at a cooler temp compared to OEM. I also got the light when it has suddenly got 28F degrees out very quickly. I guess my question is that, could it be my upgraded cooling system and the very abrupt decrease in temperature be causing it to throw the code? I have driven it for about 400 miles with the upgrades and no issues until the weather shift. I don't wanna spend the time to change the thermostat out if its doing it job, and its not broken. Can this code cause any real damage if it's keeping it from getting really hot during this cold weather?

thanks in advance guys.

 

[Just a Hunter]

P0128 is a low concern fault so long as your not having any signs of overheating.

Typically, modern vehicles monitor how long it takes to reach a given temp, and monitors temps thereafter .

This info is shared with the pcm which in turn can control the air fuel ratio.

With this being said. The idea of keeping an engine running as cool as possible may not be in its best interest. Often enough you risk the engine running lean which in turn can cause other problems .

Xterras can be funny about the brand thermostat they like, and if this was my vehicle I would swap yours out for a new one thats oem.

 

[boyer]

Z1 normally puts out tried and true stuff. Clear the code, drive it some, then call Z1 if there is an issue. I thought a bunch of guys on here ran the 350Z thermostat with no issues.

 

[Jard]

That is the first time I ha e seen that code.
I will be reading up about it.

As stated above, awesome information.

 

[RamTest]

Can this code cause any real damage if it's keeping it from getting really hot during this cold weather?

What do you mean "getting really hot during this cold weather" ? How hot is it getting? How hot does it get in summer ?

 

[Pvyton_]

What do you mean "getting really hot during this cold weather" ? How hot is it getting? How hot does it get in summer ?

What do you mean "getting really hot during this cold weather" ? How hot is it getting? How hot does it get in summer ?

What I mean is that if I'm flashing the code during extremely cold weather, can it cause damage. From my understanding that code means the coolant and engine is taking longer then it wants to get up to operating temperature. The gauge is always at normal temp, always in the same just below halfway mark.

 

[Jard]

You want the motor to reach normal operating temp as fast as possible, so the emissions will stay as low as possible. It will cause some fraction of damage, just because cold oil does not lubricant well and cold coolant does not retain heat well. If everything is still "cold" then the ecu tells the injectors to stay open just a little longer, to help speed up the heating cycle.

The biggest reason for a colder tstat, is performance. It is not the same as older carbed or early fuel injection cars though, but it can still be noticed.
Because, if the ecu thinks the motor is still under temp, then it needs to dump more fuel in to "warm" it up, more fuel means more power and faster warm up times. If you are a high compression motor or turbocharged motor this can be quite noticeable.

 

[RamTest]

The only risk of damage from running too cold is possibly to the cats from constantly running in open loop (below 158°) which maintains a richer fuel mixture.
Rich enough to toast a cat ? Hard to say but, although quite durable, I can say those cats are mighty expensive.

 

[mschwab327]

Is it full of anti freeze? Did you damage the wiring for the temperature sensors?
Did you somehow disconnect the temp sensor their is 2 of them one for gauge and one for the ecm. With engine cold remove rad cap it should be full make sure you didn’t get the caps switched the extended long cap with a spring on the underside goes on the plastic bottle.

 

[smj999smj]

I got $10 bucks that says if you replace the thermostat with a stock Nissan thermostat, the code goes away.