hvdb

Hi All,

I recently purchase 2012 Porsche Panamera S Hybrid and I have a hybrid Fault code P055600 Implausible Signal. My garage did a Smoke test and replaced the brake sensor and brake distance sensor.

The conditions are:
- “Fault Hybrid System” yellow warning pops up.
- Hybrid system itself works perfectly when erasing the code with a code scanner, but the error comes back mostly after a restart.
- On the freeway driving ore after a reset it never fails.
- The ignition do not start at the first try (almost like it’s not detecting the brake switch), it always starts with the second attempt.

If anyone can point out the possible issues here, please help!

Shrike071

Are you using a PIWIS to scan? Normally, that code is for the brake pressure booster.

hvdb

We did not use a PIWIS scanner but Odis. We checked te brake pressure booster. I see no other option than going to a porsche dealer for a PIWIS scan.

gogoporsche

Hello, I am a French mechanic, sorry if my English is bad.
I have the same problem on a cayenne hybrid, my problem is identical to yours.
did you find the solution??
Thanks a lot

amphicar770

P055600 Pressure Sender For Brake Booster - Implausible Signal

Seems to be a common problem. There is issue where a leak develops. Electric booster pump then runs constantly until it burns itself out. Mine was fixed under CPO. They replaced the pump, the vacuum lines and the relay.

Here is related TSB
https://static.nhtsa.gov/odi/tsbs/20...53443-6871.pdf

gogoporsche

okay, we changed the pump and tested and checked the whole circuit, there is no leak.

what surprises me is that the ignition does not start on the first try, it always starts on the second try.

is this always the case when there is the p055600?

amphicar770

When mine was bad, it still started on first try.

Benamera

I have a 2014 Panamera e-hybrid and can’t get my car to start. It started showing hybrid fault messages one day, then upon startup just gave a hybrid fault and said to take it to the shop… but would not turn over.

I had it towed to a mechanic who cleared all the codes for me, and it worked fine for a few weeks. And then began giving hybrid fault messages on the dash again. It ran for another two weeks occasionally giving that warning and now will not start and present the same hybrid fault message on the dash. The OBD two scanner shows P0556 error code.

when you had the brake vacuum issue serviced, did it put an end to your hybrid fault messages?

Marcus13190

Control or change relay under driver seat. This relay is 100








Control this fuse :

amphicar770

This was a persistent problem on my 2014. Partly resolved when they replaced the pump and hoses up front. Eventually they replaced evap relays and hoses from fuel tank all the way to manifold. That fixed. It. Took several visits and multiple warranty claims.

Benamera

thank you for that reply! It is super helpful. I’m admittedly a complete noob at this kind of thing, so your photos are really helpful.


I located that relay under my passenger seat but it doesn’t want to come out too easily and I’m paranoid about forcing it. Is there any trick to it, or am I just being too timid with it.

I also popped open the fuse box, thinking I’d check for a spent one in 31…. My 31 is empty, and so is most of that row I don’t suspect that’s an issue since it’s been that way since I bought it. 🤔

im also having a hell of a time getting a replacement relay that actually suggests it’s compatible. I’ve found several online that seem like they ought to be, but I’d rather not guess. Any chance you have a link to a legit match?

Marcus13190

hi, name of this relay is 100 (old is 644) réf is 4H0 951 253

Benamera

Is this an appropriate replacement? Any trick to getting the old one or, or just pull harder? 😅

https://www.fcpeuro.com/products/vw-...-vag-4h0951253

Marcus13190

You need pull harder
Relay 100 replace the 644, but 644 it's ok to test it.