MS2 5 Volt issues

[E36Turbo]

So my megasquirt has been intermittently just not powering on!

I've traced the issue down to the 5 volt bus is only measuring 2.2 volts.

I disconnected the tps in case that was the fault, and with everything but power disconnected it still exists.

D19 is measuring 2.2 volts on one side and about 600 ohms across.

C22 also measures 600 ohms.

D19 is measuring 12 volts on high side, and 2.2 volts on the other side.

Please help!!


Sent from my iPhone using Tapatalk

[slow_hemi6]

Is the regulator getting hot? Does the regulator have a good connection on it's ground pin?

[E36Turbo]

It's the pcb 3.57 pre assembled. What's regulator labelled as?


Sent from my iPhone using Tapatalk

[slow_hemi6]

Should be U5. http://www.msextra.com/doc/pdf/html/MS2 ... 4-171.html

[E36Turbo]

Is that all I should be looking for? Is it common to see less than 5 volts when regulator goes?


Sent from my iPhone using Tapatalk

[slow_hemi6]

It is not common to have a faulty regulator. They are fairly robust device.

[DaveEFI]

IMHO, an intermittent fault like this is far more likely on the external 5v wiring than in MS itself. Unless you are seeing the fault on the bench with just a Stim connected.

If it only happens on the car, I'd be inclined to arrange an easy way to measure the current in the 5v to the sensors, etc. A breakout board can be very useful for this.

[E36Turbo]

So my megasquirt hooks up to an amphenol connector for sensors then it gets power separately, the fault exists with all my sensors unplugged.

So my symptoms are definitely a 5 volt fault?


Sent from my iPhone using Tapatalk

[rickb794]

Sensors unplugged still leaves the wire harness. Which is where the problem is most likely.

[slow_hemi6]

Pulling too much current (a short or overload) should cause a lot of heat in the reg and make it shut down.

[E36Turbo]

No faults in this connector..


Sent from my iPhone using Tapatalk

[E36Turbo]

Nothing warm on U5, my fuel injectors are ticking... Which is kind of odd..


Sent from my iPhone using Tapatalk

[E36Turbo]

JS12:
JS12C: 2.50
Q9: 11.53
Q12: 11.57
D3: 11.50
U5: 2.53
D9: 2.55

S5: I think you are referring to JS5, I get 0.03, this is my tach output running to pad 7 on the db15

+5V holes: 2.48
D9: 2.4
U5: 2.5
D19: 0
Cpu pins 1,20,31: 2.5 volts


Sent from my iPhone using Tapatalk

[E36Turbo]

I also tried removing d19 but no change


Sent from my iPhone using Tapatalk

[slow_hemi6]

Was there voltage at S12? If there was 12V there and S12C is 2.5v then look at C16 or D12.

[E36Turbo]

I couldn't find S12. Unless you mean JS12


Sent from my iPhone using Tapatalk

[slow_hemi6]

Just measure both sides of D10. It's anode side should be 12V and cathode side should be what you see at S12C.

[E36Turbo]

And if that's bad what is my issue?


Sent from my iPhone using Tapatalk

[slow_hemi6]

It should be about the same as you got for Q9 Q12 D3 on the anode side. Just trying to be thorough. C16 or D12 are what I would suspect pulling the voltage to the regs input down. If you had the MS2 daughter card out checking voltages then it is unlikely the IAC driver could be involved.

[E36Turbo]

I didn't have daughter board out but I will check again!


Sent from my iPhone using Tapatalk