Lythics

On 4/15/2022 at 10:25 AM, Linas.P said:

Ok - now car is definitively fixed and I am saying it because I am 99% confident of what has caused it.

So, the night before the fault I took it for car wash, I washed it and because after washing the engine was warm I thought I will rev it and see how smoothly it revs, so launch the car few times revved it out probably 5000+ RPM, came back home and next day it would not start.

Yesterday after finally somehow clearing the immobiliser fault, it let the engine warm-up revved it few times and noticed that after revving engine nearly stalls. This led me to conclusion that there is still some other issues with fuel delivery maybe pump, HP pump, fuel pressure sensor or something in between, but as car was still staring I was mucking about with immobilisers and various stuff and eventually it would not start again. Could not figure out why, but thought enough for tonight, immobiliser comms got corrupted again or something and left it until today.

Today I repeated what I did yesterday, changed immobiliser, reset and resync, but was still getting trouble starting the car. At this point I thought - I had new fuel pressure sensor anyway, because I bought it believing it may be causing issues, so I tried changing it to see what happens. Changed fuel pressure sensor and all problems are gone, even Shift Solenoid Performance and O2 Sensor codes are gone!

Now the biggest issues diagnosing it was that it is intermittent and requires special circumstances to occur (that is my "favourite" type of issues, because they nearly impossible to diagnose). So the way to reproduce the issue is as follows, start the car, rev the engine past 5000-6000RPM, this causes fuel pressure sensor malfunction, which as result interrupts and corrupts communication on LIN network (which is 5V and communicates between immobiliser, wheel lock and certification ECU), like it is not enough, you can start the car again and you won't know there is an issue as long as you don't lock it. So what caused the issue yesterday was that I locked the car at some point when trying to link the keys. If you lock the car something happens with immobiliser and it won't work again, so when you come to unlock it next day car won't start with immobiliser communication error. Now in theory if you can clear the error from immobiliser, car would start and run again until you reach high RPM and cycle repeats, but for some reason the error was not clearing (I don't know why, maybe again because immobilisers somehow corrupts itself). In my case I had to use another immobiliser for the code to clear. Anyhow if one never reaches high RPM then this issue does not repeat itself and fuel pressure sensor works fine when idle or with engine off, so when I was measuring it there was no issue with it. Basically I took out dashboard for nothing (although ultimately it helped me to find the issue), but I don't hate myself too much, because realistically there was no way to diagnose it to fuel pressure sensor when it was failing in this very specific intermittent way.

@Lythics and few others were right, it was fuel pressure sensor, but I knew this could be the case and have actually checked it before without finding any issue. 

And what is conclusion - modern cars are complex and damn annoying to work on! Obviously better electrician probably would have been able to find ways to troubleshoot it properly, but where do I suppose to find them?! It is nearly impossible, I have had 4 different people to check the car and they could not diagnose it.

I’ll send you the bill later lol. Glad you got it fixed brotha! 

Hey I had the same thing you described in your first post and rushed to the reply section so if you tried this before and you mentioned it in this post,I’m sorry in advanced. But try and replace your fuel pressure sensor. I had the same symptoms and that did the trick.