Hi folks! 

Im owning Skoda Fabia 1.2 HTP 2010, and when I bought it - the 'Check Engine' light was on. So, official dealer's service guy said, that it might be a fuel pump issue. ( and it sounds reasonable since this car was upgraded to LPG. Usually people run car with empty fuel tank using LPG only, so fuel pump got damage). But, once I start to investigate the problem - it becomes more and more interesting. 

First of all - I found the additional wire, that wired into the Positive 12V ignition wire (see attached image, red repaired wire). I have no idea, what is it for, but the additional wire then goes to audio system connector. I don't think it makes any sense for fuel pump issue. 

More interesting thing is that I found additional wire  from fuel pump relay ground wire - to ground in audio. What I found now is that when the ignition is ON (key in position 3, but the starter is not working now), we are getting ground on audio system. That means, that relay will be turned ON. But if I try to check the original ground wire on relay - there is no any signal. No ground, no +12V, nothing. That drives me to the idea that my ECM (ECU) died. So, I tried to replace it. But that made no any sense - the problem is the same. I double-checked all wires - all looks good. I also tried to check all fuses, I checked fuel pump (actually, I replaced it), and I also checked relay. So in a short: 

I have p0230 Fuel Pump relay circuit issue, 

all fuses are ok

ECU (ECM) tested by replacing to another. 

The symptom is: no Ground signal on fuel pump relay, no ground signal on the same PIN in ECU (ECM).

For me it looks like the algorithm of the ECU decided not to start the fuel pump, which means that 'no ground' state is a predictable and expected. But why? maybe that is some sensor fault or something else? 

Anyway, I'm waiting for your comments , also I will be happy for full step-by-step description of how ECU starts the fuel pump. 

 

Thank you all. 

Which colour wire and which connection number at the audio is/was the additional wire to the relay coil added to?

Was the wiring still like this when the replacement ECM was fitted? 

 

11 minutes ago, Wino said:

Which colour wire and which connection number at the audio is/was the additional wire to the relay coil added to?

Was the wiring still like this when the replacement ECM was fitted? 

 

So, I attached the audio connector with all additional wires. 
The brown one (with cut) is the one, where ground signal from relay was wired (find blue-yellow wire in photo with blue-purple socket for relay, last one in previous post).

the white-black is the one, which comes from broken RED wire (ignition) from fuse box. (find red broken wire on first photo in previous post. Also, it is the same on third photo - it comes on fuse with '10' in bottom line).

I'll have a look at wiring diagrams after breakfast, but I think various electrical supplies are only enabled when the fuel pump relay is energised, so maybe when the car was being used only on LPG, the previous owner 'frigged' the fuel pump relay to be forced into an energised state whenever the ignition was switched on (by connecting that blue/yellow wire to a permanent 0V. Then maybe disconnected the fuel pump itself?

 

I'm not sure if this "forcing to 0V" would damage the ECM(s), but it seems a bit unlikely.  But then, having fixed the wiring, I don't understand why you still have the error showing.

1 minute ago, Wino said:

I'll have a look at wiring diagrams after breakfast, but I think various electrical supplies are only enabled when the fuel pump relay is energised, so maybe when the car was being used only on LPG, the previous owner 'frigged' the fuel pump relay to be forced into an energised state whenever the ignition was switched on (by connecting that blue/yellow wire to a permanent 0V. Then maybe disconnected the fuel pump itself?

 

I'm not sure if this "forcing to 0V" would damage the ECM(s), but it seems a bit unlikely.  But then, having fixed the wiring, I don't understand why you still have the error showing.

the most strange thing is that the ECM does not provide 0V on that blue-yellow wire. That's make me confused most. 

Btw, VIN code is TMBEA25J2B3025628

Was the extra wire to 0V still connected into the blue/yellow when the second ECM was tried?

13 minutes ago, Wino said:

Was the extra wire to 0V still connected into the blue/yellow when the second ECM was tried?

No. I tried to start a car with restored original wiring first. 

potentially, it might be same issue with ECU. But the chance that both ECUs with the same problem is a very low i think

OK, I expect there's no problem with either ECM.

1 hour ago, Wino said:

OK, I expect there's no problem with either ECM.

I've just checked the CMP (camshaft position sensor) and there is no any voltage there even during start. Could it be the reason? 

 

Yes, I think it should have 5V on one wire probably.  What's the engine code? 

1 minute ago, Wino said:

Yes, I think it should have 5V on one wire probably.  What's the engine code? 

Not sure about the code you mean.  It's 1.2 petrol HTP (Volkswagen). Do you need other specific code? if so - how can I get it? 

 

Engine code is on the build options sticker on the boot/trunk floor.  I can probably work it out from wikipedia, but if you can photograph that sticker it would be helpful. Wiring diagrams are organised by engine code; so it is easiest to use that to navigate to the right info.  Also may appear on a sticker in the engine bay 'Motorkode' or similar, is the German name.

23 minutes ago, Wino said:

Engine code is on the build options sticker on the boot/trunk floor.  I can probably work it out from wikipedia, but if you can photograph that sticker it would be helpful. Wiring diagrams are organised by engine code; so it is easiest to use that to navigate to the right info.  Also may appear on a sticker in the engine bay 'Motorkode' or similar, is the German name.

I can't upload files anymore. 
but this might be what we are looking for:  CHFA   LNR

 

Yep, CHFA. ☺️

If built before March 2010, it should be like this

Pin 1 at cam sensor connector, the red/black wire, should have 5V relative to pin 3 the brown earth wire.  (Certainly when cranking or running, possibly just with ignition on)

Pin 1 originates from pin 64 at the engine ECU, the earth wire should have connectivity to pin 54.

 

If built from March 2010 onwards, the 5V wire is black/white and the earth is brown/blue.

1 hour ago, Wino said:

If built before March 2010, it should be like this

Pin 1 at cam sensor connector, the red/black wire, should have 5V relative to pin 3 the brown earth wire.  (Certainly when cranking or running, possibly just with ignition on)

Pin 1 originates from pin 64 at the engine ECU, the earth wire should have connectivity to pin 54.

 

If built from March 2010 onwards, the 5V wire is black/white and the earth is brown/blue.

Yep. 64 pin has connection to white-black +5V pin on sensor. And 54 pin GROUND has connection to blue-brown, but the blue-brown is wired with few brown wires inside the trunk, so it joined with just brown, which comes to 54.  Is that a factory-connection? Or additional wiring by other guys? Not sure. 

Anyway, the connection is present, but there is no supply on sensor. Could it be some immobilizer issue? 

So it really looks like that the ECU decides not to go to ignition state: no supply on cam sensor, no supply to fuel pump relay. 

The earth sounds like the factory connecton.

There is at least one other sensor fed by this 5V, I will have another look at the wiring diagram later because a fault elsewhere may be pulling down the 5V rail.

1 hour ago, Wino said:

The earth sounds like the factory connecton.

There is at least one other sensor fed by this 5V, I will have another look at the wiring diagram later because a fault elsewhere may be pulling down the 5V rail.

Thank you for your time. 
Waiting for your findings. I don't have any schemes, any documentation or anything that might help me at the moment. 

Crank sensor and MAP sensor are also fed from a 5V source (brown/white wires in both cases), but from a different ECU pin (62) so I suspect it may not be the same voltage supply. Check whether that 5V is present anyway, MAP sensor is a lot more accessible than crank sensor.

Edited 6 July, 20205 yr by Wino

18 hours ago, Wino said:

Crank sensor and MAP sensor are also fed from a 5V source (brown/white wires in both cases), but from a different ECU pin (62) so I suspect it may not be the same voltage supply. Check whether that 5V is present anyway, MAP sensor is a lot more accessible than crank sensor.

Hi. 
So, today I tried to check other sensors around the engine - found one (probably, temperature sensor, with brown and white wires), it has just 0.6V when I start the engine. Is that ok? 
2 PIN connector - brown and white. 

I have no reason to think that isn't normal.

4 minutes ago, Wino said:

I have no reason to think that isn't normal.

What do you think - could it be just immobilizer issue? . I mean generally - could immobilizer blocks all of that supply? 

 

Edited 7 July, 20205 yr by Slava

Usually if the immobiliser isn't happy it lets the engine start but then cuts it out again after a few seconds. (From what I've read, I haven't had it happen to me.)

17 minutes ago, Wino said:

Usually if the immobiliser isn't happy it lets the engine start but then cuts it out again after a few seconds. (From what I've read, I haven't had it happen to me.)

Could you please share electrical schemes for my car please?