Saturn and the bypass signal

tebriel · Post by **tebriel** » Mon Jul 24, 2006 5:16 pm

Hi all,
I've read over all of the threads that I know of dealing with the saturns/gm ignition modules, but I can't find anything that deals with how the MS2 handles the 5v bypass signal. It appears that for the msns, pin 27 will output this signal for you.

Do we just use a switch and manually turn on 5v after the car has started?
-teb

Bernard Fife · Post by **Bernard Fife** » Mon Jul 24, 2006 5:24 pm

Teb,

You can either use an external relay (shown on the HEI page: http://www.megamanual.com/ms2/GM_7pinHEI.htm), or the spare port settings (http://www.megamanual.com/ms2/spare.htm).

The FIdle is particualrly useful, since most GM set-ups use a stepper, not the FIdle port. However you may already be using the FIdle output for a TCC (in which case you'll have to use one of the other ports like knock enable and add a transistor).

Lance.

tebriel · Post by **tebriel** » Mon Jul 24, 2006 6:11 pm

Ok, so you use the generic port settings, set it to pm2, then do you just use the pin 30 on the db37, or do you need to run a jumper? I see that it says that the set value is either high or low, is high automatically 5v on the FIdle? if so that would be exactly what I need, i guess i would set the values to rpm > 0 and rpm < 250.

with power on value of 1. From the way I read it, you would want the trigger value to be 0, as the unit is powered on. This would leave the 5v off the line, until my conditions are correct.
Am I getting all of that right?

-teb

Bernard Fife · Post by **Bernard Fife** » Mon Jul 24, 2006 6:25 pm

Teb,

What I would do is try it and see (it depends on the transistor and whether it inverts the signal).

The FIdle ports grounds the FIdle, so you'll need a pull up resistor to a 5V source (such as from the proto area). The pull up resistor can be any 1K Ohm resistor. The jumper can go to the banded end of D8.

The set up the port conditions (rpm < 300) and settings (check these carefully), and you have the pin B signal on db37 pin #30.

If you have the relay board, you can use the pull up on the relay board instead of in MegaSquirt. The FIdle relay might be set up to supply a ground or 12V depending on how it's jumpered. You want it to supply 5 Volts, and I think the way to do that is to remove the jumper and connect the center hole to Vref. (Check the schematics here: http://www.bgsoflex.com/mspower/mspower_ShemV1.2.pdf)

Lance.

tebriel · Post by **tebriel** » Mon Jul 24, 2006 8:26 pm

Ok, I will do that, thanks lance! Aren't I glad i'm still around?

tebriel · Post by **tebriel** » Sat Aug 05, 2006 3:05 pm

Ok,
so I decided to use a switch instead for the bypass signal, as it's simpler and it would be good to be able to manually put it into limp mode.

However, i've been try to use the Fidle circuit to run the fans, by hooking pin 30 up to the fan relay ground pin, and using the port settings to turn the fans on above 180F. But, when i tested it out, that wire is always grounded, it doesn't go on or off... also, one would think that it would run the relay, but it doesn't the fans don't turn on. When I run a normal ground wire going to the block into the relay, then the fans turn on.
I just updated the firmware to 2.36, but this didn't make any difference.

Any tips on what I'm doing wrong?
-teb

bluetrepidation · Post by **bluetrepidation** » Sat Aug 05, 2006 3:46 pm

Hey I have both these things set up on my Saturn. If you need some details I can get them for you. I am using one of the spare LEDs for my bypass signal and the Fidle output for my fan.

PM2- FIdle Check mark Enable
Coolant > 84.99 Hysteresis 5
No second condition

Power on value 0
Triggered value 1

PM3- Injector LED Check mark Enabled
RPM < 300 Hysteresis 5
No second condition

Power on value 0
Triggered Value 1

Is the car running yet? If not I'd stick with a switch for the bypass till you get all the other bugs worked out. Then you'll want to hook it up this way. Also note that you may need to increase the vale of 300 depending on how low your compression is. Sometimes the started can spin it past 300 RPM. Let me know how things work out.

A.J.

bluetrepidation · Post by **bluetrepidation** » Sat Aug 05, 2006 3:48 pm

I would test the FIdle output with a lamp connected to a good 12 volt source. Where did you get your MSII? Is the FIdle circuit even installed?

A.J.

tebriel · Post by **tebriel** » Sun Aug 06, 2006 7:22 am

i built the ms2 myself, i would think the circuit would be installed, i installed everything on there except c11 and c30 i think.. and then jumpered d1 and d2. so for FIdle, does yours ground and then unground when it's supposed to? as for the bypass, it seems to be working fine with the switch so I'll probably just leave it. I don't even need to switch it back to limp mode most of the time.
-teb

bluetrepidation · Post by **bluetrepidation** » Sun Aug 06, 2006 7:38 am

Yes mine grounds. But I had the same problem at one point. I found I had the ground my MS in 3 places. A direct run to the ignition control module. A ground to the original ECU. Finally a run through the firewall to a good grounding point to the frame. This solved my intermittent fan issue.

A.J.