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G4 Xtreme aux voltage problem

Rui Esteves

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I'm finishing my Xtreme installation and everything was ok still last Saturday when I did the tacho and check-engine light connections. When I did the test if it was all ok, I switched off the key the engine did not stop running.

So, I found that, since them, all of my auxiliaries have 8 volt.

I disconnected all of them and disabled in the PCLink, too, but they still having 8 volt !!!

I do not understand what happened.

It's possible that the ecu to be damaged?

Can anyone help me, please?





PS: here is my wiring diagram



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Thanhs for your reply Martin. I do not understand what's wrong with the relay 1... what do you mean with is odd? The first relay command all the others. About the SW1, is to switch between to boost tables and inform the G4 to switch on the relay 6 (aux 2) and switch on the water/meth injection. Rui

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Hi Rui,

SW1 needs to be connected to ground. The DI has an internal pull up resistor, so a ground switch is required to change its state.

The most common issue with ECUs not shutting off is either as Martin said backfeeding through AUX channels or a relay latching on due to a wiring configuration. I am also confused with the link drawn in relay one.

On a side note, Knock sensors are meant to be wired to dedicated knock channels and not analogue volt channels.

Going forward can you please explain how relay one is configured?

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Hi Phil Let me try to explain what I thought to do with the 6 relays: when the key is switch on, the first relay only turn on the ecu and all of the others five (1-ecu; 2-coils; 3-fuel pump; 4-injectors; 5-ebc, isc and purge valve; 5- water/meth injection. The SW1 is a dashboard switch: when it is closed, the aux2 turn on the relay 6 with a switching condition in DI1, turning on the meth injection system and exchanging to the 'race' tables. The system includes a Boost-Safe output (grounded when active) that activates whenever the system is armed and runs out of fluid or an error code is flashing. I used it as digital imput DI2 to build a safe condition (tables, ignition retarding, etc). Thanks for remember knock sensors wiring. That is a mistake mine in diagram. I will correct it. Can you explain the possible causes of the exactly 8 volt (and not 12 volt) in all aux? Still last Saturday, the ecu was working very well (so the car). I disconnected all the devices wired to the aux and disabled all of them in PCLink, but they still having the 8 volt... I appreciate your help if you please. Rui

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I can understand how you have wired the relay's ( I think ) similar to how I wire them. The C.E Light. The ECU earths the C.E. Light but what about the power side of the bulb? Does the power to the bulb turn off with ign sw, as if not power can track through the bulb into the ECU and keep everything on.

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Thanks for remember Matt, but I checked the engine light when I wired it. It's ok. The bulb powers off when the key is switched off. Infortunatly, I think my problem is more complicated. This weekend, after read the technical notes about 'Avoiding Auxiliary Output Back-feeding' I did a review of all installation searching a mistake like a solenoid wired to an auxiliary output that has its power supply wired directly to the battery. I didn't find anything wrong. So, I disconected all devices from ecu and wired the ecu directly to the oem main relay powered by the switch key. Now, the ecu hasn't any aux wired. After, I measured the aux outputs again and all of then have 8 volt (from 1 to 8). The aux 9 and 10 measured 0 volt. I am completely lost... anyone have any suggestion? Can the ecu to be damaged? Rui PS - here is my diagram with all of diconections I did.

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right... ive looked at this again..


relay 1...

the way in which this is wired means there is a permanent feed to the ecu at all times.


so no matter its position there is an output to the ecu..

the way to correct this is by removing link and coming from connector 87 for both wires.

see attachement for back feed...

and attachment for fix.

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