Quote Originally Posted by vce1232000 View Post
I had the P0089 code pop back up a few times again under WOT while hard. So I the lpfp A4 fuel pump control unit with RS4 control unit and the P0089 code never popped back up again. Guess if your tuned or KO4 & it makes the stock A4 unit max out on the duty cycle and trigger the cel.
Yes, that exactly seems to be the case...Seems like the LPFP CM might actually be more to blame than the LP fuel sensor on the HPFP?

Returnless fuel systems are computer controlled and the fuel pump output and actual fuel rail pressure is determined by a fuel pressure sensor on the rail that uses the temperature of the fuel to determine the actual pressure. The Powertrain control module or Engine control module (PCM/ECM) has determined that the fuel pressure commanded is not within specifications and will set the DTC P0089.
As for me, I looked over this thread for YEARS but would happily walk on by because I never once got this error code...Welp, things have changed

Code:
p0089
valve for fuel metering
n290
implausible signal
I've been pushing my car super hard for the past 2-3 months but it never triggered it until now. I did 2 or 3 REAL hard pulls a few days ago and just wanted to make sure no silent codes (cuz no MIL) came up...Well clearly they did. I know the N290 is actually the LP fuel sensor on the HPFP (thrust sensor?) and I got that replaced at my local dealership 2 years ago under the extended warranty. As well, like last week I replaced my cam follower and both it and my HPFP were in perfectly fine shape. Have replaced my fuel filter and LPFP control module within the last 15k miles as well

No side effects so I just cleared it and it better not come back or else I'll have to really investigate...Probably with freebies like checking to make sure I screwed the thrust sensor back on tightly enough, all the fuel lines going to the HPFP are in good shape, etc.....