I live in CA and it’s time for smog on my 03 evo. I am getting P0300 and have changed plugs and gapped them correctly. All emissions equipment is there but I am having two issues. P0300 which I cannot tune out of the stock Rom (updated to the newest version). I am also able to set all monitors except the EGR. Please advise if these two are separate issues or can be causing each other.

 

Update:

driven 100 miles and still no dice. Deylag here helped me log the car and we see the knock sensor picking up noise even from a stand still. Anytime I take off or shift gears there’s a count. All monitors have set except EGR and has a current Pending code for P0300. Car does still have HKS 272/272 in it but wasn’t a problem before and All logging is with boost being sub 10 psi. No other codes found in the system. Any advice would be great.

 

Update, over 300 miles and it hasn’t set. P0300 on highway and at idle. I removed the egr to check vacuum on the top port. I used a hand pump to get to 15 psi of vacuum and it bled off. Are these supposed to hold vacuum?

 

I’ll check my spare EGR. I think it should hold and not bleed off, but don’t know what vacuum is on that port. I’ll just double check tomorrow.

 

thank you, I replaced my egr but still getting the p0300 code and egr monitor still won’t set. No codes other than p0300 and all other readiness is complete .

does anyone know if the pending dtc will keep the monitor from setting?

 

Bump, still have not figured out a solution. Is there a way of relocating the knock sensor somewhere that hears less noise?

 

Bump, swapped back to stock cams and drove 33 miles today and light came on for p0300. Erased and came back within 10 miles. Came on again two more times within 20 minutes. Any ideas here?

 

Is it possible front o2 sensor toast?

 

would that cause this issue? I’ve never replaced it in my ownership. I bought the car in 2017 with 95k on it and I currently have 113k on it now.

 

You can usually see that in Evoscan where the Front o2 sensor either shows a frozen value or doesn't match up with the rear o2. This would produce a different DTC as well.

 

Update:

car passed smog, egr set with a new battery installed with stock rom and stock cams.I’m unsure if it’s something mechanical or not . As the car heated up and driven for longer periods of time, the p0300 would come on sooner and sooner mileage driven wise. Example. Start up and warm up. Drive 30 miles and light comes on. Clear the code, drive 10 miles and would pop up again, clear the code and it does it again within 10 miles.

 

Did you check your O2 sensors as suggested?

 

my o2’s both show voltage but how do you test if it’s bad?

 

P0300 can be disabled but you need the updated definitions. I don't know if this is 100 percent possible on the stock rom without altering the CVN.

 

disabling in a stock rom does change cvn . Verified .