Cupra R Short Circuit to ground?

[ttnuk]

hello guys, got an issue with my cupra r, it turns over but it wont fire, the fuel pump wont prime or run.

these are the codes that come up,

camshaft timing control; short circuit to ground
boost pressure control valve; open circuit
boost pressur regulation valve; short circuit to ground
tank ventilation valve; short circuit to ground
fuel injector cylinder 1; short circuit to ground
fuel injector cylinder 2; short circuit to ground
fuel injector cylinder 3; short circuit to ground
fuel injector cylinder 4; short circuit to ground
fuel level sensor; short circuit to positive or open circuit
outside temp sensor; short circuit to positive or open circuit

if anybody has any ideas it would be great, i have replaced a few sensors, cleaned any visible earths and replaced the fuel pump and relay.

 

[mty12345]

Have you tried the fuel pump relay?

 

[ttnuk]

Have you tried the fuel pump relay?

yes sorry that has also been replaced with a new genuine relay

 

[mty12345]

Cool, i take it ytou've checked all fuses including the big metal ones on top of the battery? What about the other relay that is the main power supply relay? The fact you have all those multiple codes would definitely push me towards a relay or possibly a fuse. Failing that then you could try removing the dash cluster and checking the purple and green plugs into the back of there. IF any of them are loose or corroded that can cause a similar issue.

 

[ttnuk]

Cool, i take it ytou've checked all fuses including the big metal ones on top of the battery? What about the other relay that is the main power supply relay? The fact you have all those multiple codes would definitely push me towards a relay or possibly a fuse. Failing that then you could try removing the dash cluster and checking the purple and green plugs into the back of there. IF any of them are loose or corroded that can cause a similar issue.

yes i have checked, will check again just to be sure! what number is the main power supply relay? thank you

 

[mty12345]

It's the one (usually) labeled 100 by the fuel pump relay under the dash. pic here>>>> https://uk-mkivs.net/topic/88679-fuel-pump-relay-location/

 

[ttnuk]

It's the one (usually) labeled 100 by the fuel pump relay under the dash. pic here>>>> https://uk-mkivs.net/topic/88679-fuel-pump-relay-location/

just replaced that relay with a known working one, still nothing!

 

[mty12345]

Hmmm, i'm running out of ideas tbh mate. Like i said earlier i'd check the 2 big plugs on the back of the dash binicle, it only takes 2 mins to remove. Maybe the ignition switch or a wiring issue around that relay panel... check the big cables are nice and tight where they join that panel and that you are getting 12volts to there.

I don't have access to the full wiring diagrams anymore, but whatever the issue is will obviously be where all those componants share a common power connection. In my mind that can only really be the few places i've mentioned above.

 

[ttnuk]

got the multimeter out again, fuse 28 voltage is jumping up to 1.4v and back down to 0v constantly with ignition on or off, getting the same at the pump?

 

[Gokiwi64]

Im going to guess that you have a short in a wiring loom or a very bad negative connection somewhere.

Check the main negative battery to chassis, look for any obvious signs of corrosion, melted plugs or damage. You could try running a cable direct from the battery negative to the engine block and see what happens.

 

[ttnuk]

Im going to guess that you have a short in a wiring loom or a very bad negative connection somewhere.

Check the main negative battery to chassis, look for any obvious signs of corrosion, melted plugs or damage. You could try running a cable direct from the battery negative to the engine block and see what happens.

all earths were removed and cleaned last week, sadly nothing changed

 

[ttnuk]

i now have 12v at fuse 28 and 1.8v at the pump with ignition on, when cranking the voltage drops and jumps about under 5v.

 

[mty12345]

I don't think that the pump is the issue. The key lies in those multiple codes IMO. Short-to-ground codes don't usually indicate a ground problem, especially when you have multiple ones. They usually mean the + voltage is missing, which could result from a broken or corroded supply connection, or a blown fuse, or bad relay or switch that is common to all the sensors, valves, etc., that are throwing codes.

I know the fuel pump relay definitely controls the injectors, could the replacement one also be faulty?

 

[Gokiwi64]

Having done some "digging" I would change my idea to that of mty's , its power missing , I know that quite a few Golf owners have complained about the power distribution module on top of the battery causing problems and in some case have reported similar (but not exactly the same) issues.