3pin ecu trouble

myrxfromTCC · Post by **myrxfromTCC** » Thu Apr 03, 2008 3:20 pm

hey i have read
Boyce thread and his issue with starting
Ok guys, here it is:
1986 Subaru XT GL-10 EA82-T engine/5spd
40k miles on engine, car runs great other than starting problem....

I get a Code 12 when checking ecu (Starting switch on or off while starting). This code may or may not be related to starting problem?

Here is the problem:
Engine wont start unless you hold pedal down and crank it over about 3 times.
If you try to start it normally it idles at 300rpm for 2 secs then dies, then you have to hold pedal down and it starts and runs normal and idles normal.

my rx was doing the same but now it has gone one step further my ecu when you turn the acc on will no longer display codes instead all i get is a faint constant glow when i try to start car all i get is one fire then nothing even if i try pushing the throttle to the floor does this mean my ecu is dead? i think my code was 13 not 12 though any help / advice would be appreciated

BrennyV · Post by **BrennyV** » Thu Apr 03, 2008 4:02 pm

you have checked all ya sensors? afm/tps etc etc

Gannon · Post by **Gannon** » Thu Apr 03, 2008 7:05 pm

try disconnecting the battery overnight and try in the morning.

When you say

myrxfromTCC wrote:a faint constant glow

do you mean from the LED on the ecu?

Does the engine crank over ok?

PM "boyce" and see what he did to fix it.

Don't underestimate the importance of punctuation in a post. Its very hard to read when there are no 'comma's' or 'full stops'

myrxfromTCC · Post by **myrxfromTCC** » Fri Apr 04, 2008 12:51 pm

benny
i have not checked sensors i will do so, can you please explain what the tps and afm i am guessing afm is air flow meter but not sure what tps is.
i do not have a manual that covers the turbo or efi model so i am kind of flying blind my other L series subys have all been carby thanks again

suparoo
i have tryed battery off over night. but no change. some times when i play around with the ecu power connector it will start for about 10 to 15 mins then the engine will just cut out even if you push the throttle pedal
the engine cranks over ok but will not start except on rare occasions.

The faint glow is coming from the ecu yes. but at the same time the dash ecs light flickers just before the engine cuts out.

i will also pm boyce to find out what he did to solve the problem thanks again all advice is welcome

twilightprotege · Post by **twilightprotege** » Sat Apr 05, 2008 10:16 pm

pls post what boyce said. i have similar issues with my RX (see showthread.php?t=9449 )

tps = throttle position sensor

steptoe · Post by **steptoe** » Mon Apr 07, 2008 12:28 am

I think the tps on these is more a switch to tell ecu the throttle is either open or closed....I think

Have you been playing with it and then this happened or did it just develop?

myrxfromTCC · Post by **myrxfromTCC** » Tue Apr 08, 2008 12:58 pm

thanks twilightprotege and steptoe
i have yet to here fom Boyce but when i do i will post how he fixed it.
The problem just developed but one thing i have not mention and i think i should is that if i disconnect the ecu the engine behaves the same as when it is connected i get one quick fire then it stall but wont fire again i am thinking the ecu is not responding what do you all think.
thanks

steptoe · Post by **steptoe** » Wed Apr 09, 2008 12:22 pm

the ecu disconnected won't open injectors or send power to fuel pump if it is like mine

Gannon · Post by **Gannon** » Wed Apr 09, 2008 5:18 pm

Its all to do with the start switch wire.

If the ECU doesnt get that "start signal" when you turn the key, its gonna have trouble starting. I can assure you that.

Find what pin of the ECU is the start signal, and temporarily connect a wire from the starter motor wire to this pin, see if the code goes away and if the car starts better.

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Wed Apr 09, 2008 9:32 pm

You could also have a faulty connection to the water temp sensor, its the one infront of turbo on the manifold. Or you could have an issue with the AFM.

twilightprotege · Post by **twilightprotege** » Thu Apr 10, 2008 9:21 am

i didnt know there was a water temp in front of the turbo. lucky i checked, the resistance between the terminals was inconsistent due to (probably) a little bit of corosion on the terminals. cleaned that up and the resistance is good. will see if that changes anything

myrxfromTCC · Post by **myrxfromTCC** » Fri Apr 11, 2008 1:14 pm

my ecu when you turn the acc on will no longer display codes instead all i get is a faint constant glow from the LED on the ecu, therefore i am unable to read what error codes are stored on ecu.
my fuel pump still pumps when the ecu is disconected.

does anyone know how to reset the ecu?
I have only found one test (green 'T' shaped) connector currently disconected form its mating part. Others have told me there should be two connectors one black pair and one green pair to test the ecu.
thanks

Gannon · Post by **Gannon** » Fri Apr 11, 2008 4:23 pm

The ECU shouldnt be doing anything with the accessories on.

The other green plug should be taped to the one you found about 5cm up the wire

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Fri Apr 11, 2008 6:23 pm

Question, Is it an original turbo car or a conversion?

myrxfromTCC · Post by **myrxfromTCC** » Sat Apr 12, 2008 11:47 am

the car is an original turbo.

thanks suparoo i will see if i can find it much easier if you know where to look thanks.
the dull constant glow is what has me thinking the ecu is not working properly and may need replacing but i dont have another one to swap over and test.

YouTube · Post by **El_Freddo** » Mon Apr 14, 2008 12:31 pm

Suby Wan Kenobi wrote:Question, Is it an original turbo car or a conversion?

This was my thoughts too.

Being an 86 this would be a Flapper style AFM... I would say that if the ECU was on the way out it'd be dead - i've never heard of an ECU dying like other components in the car can.

Is there any wiring that has been done on the car recently that you know of? Got an immobiliser installed?

The throttle position sensors on this model L is just a simple "on/off" switch that basically tells the ECU that the throttle is closed (idle) or open (everything above idle). The later Hotwire/4plug ECU has a "pendulim" TPS, allows the computer to know how wide the throttle is open at any given time.

I don't know if the 3 plug/Flapper AFM system has an air bleed solenoid behind the throttle body for cold starts, but if it does this may not be funtioning properly, possibly causing the hard to start/stalling issues your expereincing.

These MPFI systems can be a PITA but once they're working well and you know a bit about them they go really well and are pretty easy to keep them sweet.

Good luck with it and let us know how it goes.

Cheers

Bennie

myrxfromTCC · Post by **myrxfromTCC** » Mon Apr 14, 2008 1:12 pm

thanks to all those that have posted some very useful information. On the week end we were able to find what was causing the intermitent ecu problems which progressed to not being able to start and unusual ecu led display. The problem has been traced to a loose/stripped manifold bolt which was also used as an earthing point.
Once this was fixed we have no trouble starting the car hot/cold however the ecu is still displaying error code 12 when the ignition is on. Could this be an old error code that has not been reset?
I have tryed connecting the green test plug but can't see any change in code. As of yet i have not tryed to reset ecu with battery off overnight. I have tried to probe back from the distributer to the ecu with no success yet.
THANKS again for all the help.

YouTube · Post by **El_Freddo** » Mon Apr 14, 2008 1:26 pm

You really only need to leave the battery off for 30 seconds from memory, I usually give it 2 -3 minutes and it clears with that.

Let us know what happens after you clear the memory (should give a 7 flash output meaning an aussie delivered ECU).

Cheers

Bennie

twilightprotege · Post by **twilightprotege** » Mon Apr 14, 2008 8:45 pm

i get 12 on startup as well. as soon as the car starts the code goes. i'm going to be checking the connectors in relation to the neutral switch tonight/tomorrow

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