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Ben Newell

Strange Output Behaviour - G4 Extreme

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Hi, I'm after some assistance with a G4 Extreme ECU.  It's doing some strange things with outputs, ie injector tick when not running, aux outputs staying live when the key goes off, fuel pumps staying on when the key's switched off etc.  I've seen the wiring diagrams and have it wired in correctly with a main relay switching ecu power and power to trigger the fuel + spark relays, but still to no avail.

I've taken measurements from the output pins on the ECU and have some rather strange results.  IE I'm getting +12v from aux channels!

Could someone take a look at the below readings please, I'm assuming there's a blown power transistor somewhere.

PORT A

======

Pin

1 +0.48v

2 +0.43v

3 +0.43v

4  +0.44v

5 +14v (input)

6  +8.03v

7 0v

8 0v

9 0v

==10 0v

11 0v

12 0v

13 0v

14 0v

15 +5v

16 +5v

17 0v

==18  +12.97v

19 +12.95v

20 +12.94v

21 +12.94v

22 0v

23 0v

24 0v

25 0v (grounded for test)

==26 0v

27 +12.59v

28 0v

29 +12.59v

30 0v

31 0v

32 +5v

33 0v

34 0v

 

PORTB

=====

Pin

1 +0.74v

2 +0.68v

3 +0.68v

4  +0.68v

5 +14v (input)

6  +5.03v

7 +5.02v

8 0v

9 0v

==10 +7.3v

11 +7.3v

12 0v

13 0v

14 0v

15 0v

16 0v

17 0v

==18  +14.00v

19 0v

20 +10.66v

21 0v

22 0v

23 0v

24 0v

25 0v

==26 +14.00v

27 +12.59v

28 0v

29 0v

30 0v

31 0v

32 0v

33 0v

34 0v

 

I'll attach the PCL shortly.

Thanks

Ben

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and after a factory reset:

PORT A

======

Pin

1 +0.73v

2 +0.73v

3 +0.73v

4  +0.73v

5 +14v (input)

6  +8.03v

7 0v

8 0v

9 0v

==10 0v

11 0v

12 0v

13 0v

14 0v

15 +5v

16 +5v

17 0v

==18  +12.97v

19 +12.95v

20 +12.94v

21 +12.94v

22 0v

23 0v

24 0v

25 0v (grounded for test)

==26 0v

27 +12.59v

28 0v

29 +12.59v

30 0v

31 0v

32 +5v

33 0v

34 0v

 

PORTB

=====

Pin

1 +0.74v

2 +0.68v

3 +0.68v

4  +0.68v

5 +14v (input)

6  +5.03v

7 +5.02v

8 0v

9 0v

==10 +7.3v

11 +7.3v

12 0v

13 0v

14 0v

15 0v

16 0v

17 0v

==18  +14.00v

19 0v

20 +10.66v

21 0v

22 0v

23 0v

24 0v

25 0v

==26 +14.00v

27 +12.59v

28 0v

29 0v

30 0v

31 0v

32 0v

33 0v

34 0v

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I thought this actually, so then removed the ecu from the car and powered it up on the bench, onto three wires connected, the two +14v and a ground.

The readings I took were from the bench with nothing else connected.

Goosed ECU?

Thanks

Ben

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This could well be the case as aux 5,6,7,8 can highside drive and if the drive is set to off will read 12V

Sounds very much like you have some back feeding issues in the car.

Also if you have a fuse on the ECU supply check this has not blown.

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Hi Simon

I don't see how there could possibly be any back feeding issues considering there were only three wires connected when I performed the test, the two +14v and one ground pin.

All of the other readings were taken between the respective isolated pins and ground using a multimeter.

Do you have a list of what the readings per pin should be on a fully working unit?

The car still starts and runs but does really weird things with it's aux outputs.

With my MS3 connected - it behaves perfectly.

Thanks

Ben

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The voltages you are seeing there I would consider totally normal.

To test the Aux outputs you are much better to work through each one and use the test on function.

And monitior what they do with a load attached.

What you are seeing when the key is turned off is a powered ECU through a back feed.

If wired correctly the drives will not be able to control any devices as they all should have lost they 12V supply so even if the ECU was to ground the drive they will not turn on.

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