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Update 4 plug TT Legacy to 3 plug WRX Ecu Conversion


Guest MasterTm27

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Don\'t have the dash in so can\'t connect the cluster. I guess thinking about it now I can put a regular 12v test light on it to ground and read the flashes. The car is at my mates house 1/2hour drive away so troubleshooting at the computer all I can when I\'m not physically working on it.

Just wondering if anybody has an ecu handy that could test those 4 pins for me.

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 woz said:

Firstly gazzy2000 you are a champion this info you\'ve posted in this thread has been invaluable in getting some issues sorted in my car!

I\'m still having some troubles with the ground pins in my conversion that\'s using a 3 plug v3/4 ecu. Am I right to assume that i\'m NOT supposed to have continuity on my ecu between B136, 7,9,12,13? I think my ecu has shat itself if this is the case, the car struggles to start and doesn\'t run the best when it finally starts. I\'ve been troubleshooting the shields on pin 13 because everytime I plug in b136 pin 13 shows continuity between itself and the chassis. The wiring doesn\'t so i\'m thinking the ecu is to blame?

These 4 pins on my ecu show continuity?

84767087.jpg

Might seem silly....

Replace or clean your sparkplugs.

You may be surprised.

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Thanks for the suggestion. I put in 4 brand new plugs last week, NGK\'s. Made no difference.

I\'m pretty sure it\'s a wiring issue/ground issue because the engine ran perfectly in the car I took it out of.

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This will/should answer your PM & put the info for all to see...

b136,13 shield earth will, somewhere along the lines get an earth, but it will be supplied by the ECU.. so the test to do is with B136 unpluged 13 should not have any continity to ground, of course when you plug B136 into the ECU it will have a circuit to ground no doubt through its noise supression/protection circuitry.

So yea, with 136 unplugged and no continity to ground you have done it right (long as all the correct wires/earths/shield are jointly connected).

B136 12 is one of the earths that goes to ground on the chasis and B136 18 joins it at the same location as does B137 24, if you trace using the V3/4 wiring diagram you will see this. (there is a diagram in note 4 showing this in this thread)

B136,7 is the AFM dedicated earth (i.e. point to point from AFM to ECU) with the plug B136 unplugged it should not have continuity to ground or any other sensor earths... hense the word \'dedicated\' (yes when you plug B136 in it will/should get an earth supllied by the ECU)

B136,9 - crank and cam sensor earth (not the shields) you can solder these two wires together and simply join into pin 9, just dont get the signal and earths mixed up.. i\'d be double checking these sensors and in doing so i\'d be refering to the v3/4 diagram and colours to assist.. so trace and double check: signal wire, earth wires shield wires

so yea, dont worry too much about earthing behaviour once the ECU plugs are plugged in, just make sure its all mint/matches v3/4 wiring with it unplugged

You have to hyper-focus and truely understand whats going on, dont rush, take your time, guessing and hoping for the best dosent work here :). You will suss it, its very hard to help out over the interwebz

HINT: if you are 100% sure you have it all right and it still wont fire/run??? pull your plugs and clean them, they foule REAL easy from prior bad starts and crap running

HINT2: for the likes of tracing/distinguishing cam and crank signal & earth wires it does help alot to use an actual under manifold v3/4 loom as the colours make it easier to trace using the v3/4 diagram. in saying that it can be done using the TT loom.

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Thanks I really appreciate your help mate. I\'ve studied the wiring diagram the last couple of days so I understand 99% of it now, i\'m in the process of laying out the loom next to the car on the ground and tracing each wire to see if it\'s going to where it should. I\'ve got time off Sunday onwards so will spend many more hours with the harness and multimeter.

No doubt i\'ll re-read your posts a few more times just to double and triple check I haven\'t missed anything.

 
HINT: if you are 100% sure you have it all right and it still wont fire/run??? pull your plugs and clean them, they foule REAL easy from prior bad starts and crap running

It runs fine when i eventually get it started but it takes multiple cranks and pumps of the accelerator to get it going initially. Once it\'s warmed up it idles well. Here\'s a quick vid of it running after it has warmed up. As you can see it\'s still not the best. If it started like this from a dead cold i\'d be very happy... http://www.youtube.com/watch?v=CCUTK2eAPxE&feature=youtu.be

Once again thanks a heap and i\'ll update this thread with my progress as I go.

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Spent the afternoon tidying up the ecu wiring. Tomorrow i\'ll get some new wires for the dedicated ecu earths, tape it all up and it should be ready to go.

Gazzy do you happen to know what exactly the function of B135, Pin 2 is? (starter switch). I assume that it works something along the lines of when it sees 12 volt from the ignition switch the ecu knows that the car is starting and does some sort of fuel enrichment to help it startup? Well anyway this particular wire was connected to nothing.... So I dare say that might\'ve been the problem. ??? Will report back in a couple days when I get to work on it again.

ZLXgE.jpg

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Got it working, it was definitely B135, Pin 2 (starter switch). I tapped the wire directly from the starter +12v so it 100% knows when the car is trying to start now.

Here\'s how it started without that 1 wire connected. (And how the car was started for 3 years, in the middle of winter it needed a spray of start ya bastard and about 30seconds of cranking before it started.) http://www.youtube.com/watch?v=dXapJueFOvI&hd=1

Here\'s how it starts WITH the wire connected. http://www.youtube.com/watch?v=wRWFcBXs0gs&hd=1

Thanks again gazzy2000 without your posts I think I would\'ve given up a long time ago.

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 woz said:

Got it working, it was definitely B135, Pin 2 (starter switch). I tapped the wire directly from the starter +12v so it 100% knows when the car is trying to start now.

Here\'s how it started without that 1 wire connected. (And how the car was started for 3 years, in the middle of winter it needed a spray of start ya bastard and about 30seconds of cranking before it started.) http://www.youtube.com/watch?v=dXapJueFOvI&hd=1

Here\'s how it starts WITH the wire connected. http://www.youtube.com/watch?v=wRWFcBXs0gs&hd=1

Thanks again gazzy2000 without your posts I think I would\'ve given up a long time ago.

no problem! good job man and well done for sticking at it!! you will be stoked! :)

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  • 1 year later...
  • 11 months later...
 woz said:
Got it working, it was definitely B135, Pin 2 (starter switch). I tapped the wire directly from the starter +12v so it 100% knows when the car is trying to start now.

Here\'s how it started without that 1 wire connected. (And how the car was started for 3 years, in the middle of winter it needed a spray of start ya bastard and about 30seconds of cranking before it started.) http://www.youtube.com/watch?v=dXapJueFOvI&hd=1

Here\'s how it starts WITH the wire connected. http://www.youtube.com/watch?v=wRWFcBXs0gs&hd=1

Thanks again gazzy2000 without your posts I think I would\'ve given up a long time ago.

Mate could you explain this to me abit more

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When you start the car, or while the starter motor is cranking. The ECU adds more fuel to help the engine fire up (cranking enrichment).

So the ECU needs to know when the engine is being started, or that the starter motor is cranking.

The ECU gets a 12v cranking/starting signal from the starter motor/ignition through ECU pin 2, plug B135.

If you've done the conversion, but are having trouble getting it to fire up. Pin 2/B135 might be empty, so needs to be connected to the starter motor 12v signal wire.

I'm guessing from the above posts, that the car's original loom has no such wire. So the easiest way to do it would probably be to back probe the ignition wires and find the wire that is only hot (12v) while cranking. Then splice into this wire and connect it to ECU plug B135/pin 2.

Then when you start the engine, the ECU's cranking/starting signal wire (2/B135) will get 12v at the same time as the starter motor.

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