# Megasquirt ECU not turning on...



## BoiseMK1GTI (Jan 28, 2004)

I was autocrossing today







, but had a BIG problem... 
My battery is in the back, with the positive cable running along the passenger frame rail in the engine bay. Well, it came loose during one of my runs, and rubbed on the timing belt tensioner until it wore through the rubber sheathing, grounding the battery to the motor. This blew the fuse for my ECU, but the fuel pump would still run, and the injectors stuck open







. I ended up flooding the motor pretty badly, which is all cleared up now, not really an issue. The main problem is that, after I replaced the fuse of course, The ECU is not turning on. I am getting power through the harness, to the Connector at the ECU, but it won't switch on, and the fuel pump obviously doesn't run now either, which is really weird. I do not see anything fried in the ECU, but I am sure something could have blown without me being able to see it. Anyone know of anything I can test to see what is blown in my ECU, (what diodes, resistors, capacitors, etc. turn the ECU on) causing it to not turn on?? Thanks for any help you can give... 
MS 2.2 (Patatron's basic MSnS for 16v's)


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## eurotrashrabbit (Oct 25, 2001)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

Hook up a stimulator board to check it out it will tell you a lot


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (eurotrashrabbit)*

Hook it up to the laptop and see if you still have communications. If not you probably blew out something in the power supply section.


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*

I do not have a stim unfortunately. The ECU is not turning on, thus it is not communicating with my laptop, already tried. I am just wondering what diodes, resistors, or capacitors actually power the ECU.


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

http://www.megamanual.com/v22manual/mass.htm
Step 19 lists tests for the power supply, and a link for troubleshooting that section.


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## VWralley (Mar 30, 2002)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*

also try to re-load the firmware onto the ecu. i had a similar problem and that solved the issue for me


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (VWralley)*

Can you re-load the firmware if the ECU is not turning on, i.e. not connecting to the laptop?


_Modified by BoiseMK1GTI at 4:58 PM 5-21-2007_


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## VWralley (Mar 30, 2002)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

i have been able to sometimes (it is actually connecting, but not working with the comp or something perhaps?), but others it has had chip issues...
my old ecu would have a power issue after it sat for acouple months, id go to fire it up and the box would just kinda wig out. had to send the chip back to pat for a reflash twice. thank god for him or i woulda been out a whole ecu if i couldnt find the issue. still dont know what caused that, pat didnt build it, and couldnt find anything wrong with the assembly...


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (VWralley)*

So I should just try powering the ECU, connecting it to the computer, and re-loading the firmware?


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## VWralley (Mar 30, 2002)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

id give it a shot, it wont harm anything more than it already is...
then id def do what is suggested above http://****************.com/smile/emthup.gif


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (VWralley)*


_Quote, originally posted by *VWralley* »_then id def do what is suggested above http://****************.com/smile/emthup.gif 

What would that be? Send it back to Pat?


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## VWralley (Mar 30, 2002)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_http://www.megamanual.com/v22manual/mass.htm
Step 19 lists tests for the power supply, and a link for troubleshooting that section.

or send it back to get looked over...


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## Fox-N-It (Jul 23, 2003)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*


_Quote, originally posted by *BoiseMK1GTI* »_What would that be? 


_Quote, originally posted by *need_a_VR6* »_http://www.megamanual.com/v22manual/mass.htm
Step 19 lists tests for the power supply, and a link for troubleshooting that section.

http://****************.com/smile/emthup.gif


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (VWralley)*

Oh, yea. I was planning on checking that. If there is no power at the pins that it notes, what diodes or resistors should I look into?


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## ValveCoverGasket (Mar 20, 2002)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*


_Quote, originally posted by *BoiseMK1GTI* »_Oh, yea. I was planning on checking that. If there is no power at the pins that it notes, what diodes or resistors should I look into?

its all in the assembly page


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (ValveCoverGasket)*

So, If I am not getting the porper voltage at the chip, I should check all of the diodes and capacitors with my multimeter set to DC volts as well, correct?


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

Yes. At the end of step 19 there's a link with more detailed troubleshooting instructions.


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*

Well, I checked the pins on the chip. My multimeter when set to DC Volts, reads 0 when the two probes are touched together. When they are not touched together, the reading bounces around quite a bit. When I test any of the pins on the chip, they all read 140mV. What do you guys think?


_Modified by BoiseMK1GTI at 3:23 AM 5-22-2007_


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

Just did another little test with pins 19 and 20 on the chip. With the key off, I am getting 0 volts, like I should. Key on, I saw about 137mV.


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

19/20 should be 5v, sounds like you blew something. 
Check you page 4:
http://www.bgsoflex.com/v22/me...2.pdf
You can check for 12v with key on at the banded end of D14. If you have that then check for 5v at pin3 of U5. If that's not there, it's most likely U5 but I would pull and check the diodes on the input section (D12-16).


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*

I am getting just over 12 volts at the banded end of D14, but am getting nothing at pin 3 of U5. What exactly is U5? What type of part? Is it fairly common to find at electronics stores, or will I need to order one? 
So, if I am getting 12v at D14, and nothing at pin3 of U5, it is most likely U5? I will order one if I get a fairly positive answer whether or not that is the problem.


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

U5 is a voltage regulator part no: LM2937ET-5.0 not sure if Radio Shack will have it, but any good electronics store will. I've also had good luck with Digikey, Mouser and Newark Electronics on the web.
If you have a good multimeter you should be able to unsolder D12-16 and use the diode check to see if they're good. If you can't do that, I'd just order all those parts and replace them all.


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (need_a_VR6)*

I have replaced diodes D13, D14, and D15 already, still nothing. I am getting 12v at D14, so I think D12 is fine, since D14 gets its voltage from there. I will try to call a couple of electronics stores to see if they have the voltage regulator, and I will replace D12 and D16 as well. Any other ideas if that doesn't work? Probably the main chip?


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## need_a_VR6 (May 19, 1999)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

If you have nothing for the output of U5 the problem is before the processor chip. That being said, check for voltage at 19/20 with the processor out if you haven't already done so.


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

OK, so I still am not getting anything from the ECU. I have now replaced the Voltage Regulator at U5, and all of the Diodes in the power supply (D12-D16) except for D12, which I will replace tomorrow once Radio Shack opens. I am also considering replacing Capacitors C15-C18 which are all part of the power supply, if you guys think that might help?


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

I will also take out the processor chip and test for power between 19/20.


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## BoiseMK1GTI (Jan 28, 2004)

*Re: Megasquirt ECU not turning on... (BoiseMK1GTI)*

OK, so I am getting 12v at the banded end of D14, but nothing on the unbanded end, is this right? I am getting no voltage to the voltage regulator at U5. Any ideas what to look at? We tried replacing D14 with another new diode, and am still not getting anything. I have no voltage at any of the other diodes in the power supply circuit except for both ends of D12 and the banded end D14, nothing past that.


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