allanyeung99

Hello fellow C400 owners, I have an issue and I would like help from yall. So I got my C400 tuned by Eurofed Charlotte in November of 2019 and they did an ECU Tune Flash with DME stage 2. In January, I had a CEL on and the code was P0087, said "The Fuel pressure was too low," I had a certified shop test my HPFP since my local dealership would have charged me $300+ for diag. I cleared the code and it never came back on. Then yesterday as of October 1, I got another code related to the fuel pressure but it was P2539 which was "Low pressure fuel system sensor circuit." Also cleared it, never came back but I want to ask my fellow C400 owners, and hopefully some tuned C400s. Does anyone have this problem? I was told it could be the HPFP going bad and I was also told it has something to do with my tune. Either way, I will most likely get everything looked at, but I would like some feedback or get some ideas from you guys. Thanks~

MatthewJ

I have JB4 with fuel plug and aggressive map 6 on my C400. no fuel pump problems or CELs in the 2+yrs with piggyback.
I have heard from others that older firmware's would sometimes throw a low pressure issue.
Do you run E85? if so how much do you mix with 93?

Edit: most of the C400's I think frequent the C43/450 subforum more than the C300 one since we share the same motor and options for aftermarket with them. Might get more info there.

allanyeung99

I've been hearing that it could be my actual HPFP or that it could be my tune. But I feel like if it was the tune, wouldn't I have gotten the code like since day 1 of getting the car? I've had the tune for almost a year and its my daily. I'll prolly hit up DME and see if the tune is up to date with everything.
I'm using 93-octane only cause its hard to get E-85 here.