Ecu won't turn on

[Paulwalsh]

Hi

Just received my s7plus got it setup and car started fine and was idling good, had vacuum leak from not putting line to bov so cut the engine. Then it kept blowing the ecu fuse when I switched ignition on and now I get nothing from it won't turn fuel pump on won't connect to laptop. Any help appreciated.

Thanks Paul

[stevieturbo]

Who's wiring ?

Exactly what is the fuse covering and what rating ?

If you unplug the ecu I presume the fuse will not blow ?

[TimH]

How did you "cut" the engine?

[Paulwalsh]

Hi thanks for getting back, it's was a 10amp fuse yes if unplugged it wouldn't blow, even plugged in it wouldn't blow only when you hit ignition button. Racingcircuits wired it and been and checked everything and all spot on.

[stevieturbo]

For most part, potentially the only thing on the ecu that might draw some current is DBW.

And possibly if you're using inductive coils, but even then pretty sure no actual current of any concern is passing through the supply to the ecu.

If you have DBW, unplug the throttle and try again.

But there is no way a correctly wired ecu setup sitting at idle, or even starting should be blowing any 10A fuse. I'd be surprised if it was even pulling 1A.

One easy way to start would be unplug the two larger connectors from the ecu and power it up via only the B, middle plug.

That should eliminate most of the external power/sensor/actuator type wiring to see if the ecu is still alive and happy.

[Paulwalsh]

Hi

Yes went and unplugged everything from DBW to wideband, on there 3rd fuse it stopped blowing fuses but now does nothing at all still sends power to wideband when I hit ignition button buts that's about it laptop doesn't see it at all.

[stevieturbo]

Hi

Yes went and unplugged everything from DBW to wideband, on there 3rd fuse it stopped blowing fuses but now does nothing at all still sends power to wideband when I hit ignition button buts that's about it laptop doesn't see it at all.

On what 3rd fuse ? What wideband ?

Whilst the ecu controlled wideband may receive 12v power from an ignition ( key one ) based source, it will not heat the sensor until the ecu output is activated.

Does the ecu now have power ? Pins B1 and B7, gnd and 12v respectively.

Confirm this, then confirm comms with laptop.

Although if you've unplugged stuff and the fuse is not blowing, either there is a faulty device, or faulty wiring of some sort. Hopefully it has not harmed the ecu

[Paulwalsh]

On 3rd 10amp fuse that powers the ecu, everything plugged back in and not blowing now but doing nothing at all.

Screenshot_20220419-082851_Drive.jpg (359.77 KiB) Viewed 6919 times

[stevieturbo]

And I will repeat again.

Have you confirmed power/ground at the relevant pins on the B plug at the ecu ?

B1 ground, and in your case B13/B19 ? ( as you're backfeeding power to the lambda sensor from B7 )

When this has power, can you confirm either comms, or no comms ?

And as said before, I would be doing this with the A and C plugs disconnected to remove as much of the loom from the ecu as possible.

Or make up a lead/connector to bench test from a suitable 12v power supply.

If you're getting no comms and no sign of life, whatever the wiring or fault is, may have harmed the ecu. There is just no way it should be blowing a 10A fuse.
But I would not have been attempting to power it back up again with that wiring loom still attached.

[Paulwalsh]

Hi

Sorry yes power ground at relevant pins. No comms ,yes tried with A and C plugs out after I tried with things disconnected, maybe lack of knowledge my end but as engine was running fine and spent hours testing loom I didn't think it would be detrimental to ecu. Thanks for your help.