Check Engine Light - P0128

[SilverSlug]

Warning: "Increased Emissions" - Code P0128

Could it be anything else other than a faulty thermostat?

Air temp sensor or coolant sensor?

[SilverSlug]

And if I'm replacing the thermostat after all, should I do the water pump while I'm already in there? (currently at 92k).

Or is it overkill to replace parts that are still working just because?

[jellydoughnutt]

That’s entirely up to you.

When I got the code, I purchased the kit to replace everything.

Here’s why. Water pumps don’t tend to fail as often as they start leaking. While I was already there it gave me a chance to replace all of the rubber O-rings with news ones. I upgraded to a metal impaler water pump for piece of mind. I even slapped on new hoses, belts, sensors too. The odds are I will not have to mess with those items for another 60-75k miles hope willing.

If you have the extra funds to throw at it, and doing the work yourself, I say why not.

[SilverSlug]

Ahh good points indeed.

Where is the coolant temp sensor located? Is this something I should address while I'm in there?

Or can I get to it otherwise without tearing all the same parts out?

[jellydoughnutt]

Yeah, it's right on top of the housing. I would be pretty sure that the thermostat is the main failing point that causes this code at your mileage. My previous M3 I got the code at 84k. My current one has 92k and I just got the kit to do the job all over again.

https://drive.google.com/file/d/1oCQ...ew?usp=sharing

There are some good videos on youtube that will walk you through the entire process. Just make sure you pay attention to all the wires you disconnect because it's common for someone to forget to plug them all back in.