Unichip P0172 CEL and the FA20 Engine
 

Hey Everyone,

So I have a K&N Drop in air filter and a Unichip on my BRZ. The ran beautifully together for over a year.

I recently posed about how I had my ECM re-flashed because I was having the "idle rpm dip issue" which (only with the Unichip installed) threw a P0172 "Too rich" CEL. I also noticed my DRL blink once RPM touches 500 for a second.

I know the P0172 code has something to do with the MAF sensor and the entire intake up to the throttle body. I check for leaks, used MAF cleaner on the MAF, and cleaned everything else.

Still, I got the P0172 code about 2 days later.

I uninstalled the Unichip, called the dealer, got the ECM re-flashed and all was well...

I next reinstalled the Unichip and the thing ran like butter for 3 weeks.

Suddenly I get the same P0172 CEL. I cleaned everything AGAIN. I get the same P0172 CEL

I assumed it was the Unichip and removed it.
And now i have the Idle RPM dip issue again

Da Faq?

I think the reflash doesn't fix the problem, it just makes the ECM more tolerant of the engine's irregular data

I also noticed my average MPG is like 19MPG when things are not running smooth and around 27MPG when things feel good.

So, the 2015 BRZ has an FA20 and they ALSO have idle dip issues. Something is funky with the FA20 engine at low RPM?

I'm thinking Unichip may be pushing the readouts of the engine just enough to trigger the CEL

Subaru just says the idle RPM dip is normal as long as it doesn't throw a CEL, but it seems to be affecting tunes.

I'm pretty annoyed that my less than 2 year old new car sounds like a cricket and has DRLs that blink when my idle dips.

I have no CEL on the stock car. Where would you go from here guys?

Update:
Drove the stock car without the unichip for 50miles

At first the RPM dip was still happening, then the car started acting normal again

I would say the stock computer had to relearn the driving

So... The unichip is definitely causing P0172 codes for nothing to do with the car. I'm going to send it back to unichip to see if it's a hardware issue

I would say sell the Unichip and get a real Ecutek tune. Unichip is not very good.

@husker741 It was working out well for a year, but I think you may be right