So, I've never really had to diagnose or troubleshoot any electrical gremlins before this, everything just seemingly worked. But after installing my new engine after the car had sat for a little over a year, I cannot get my launch control to work. The car is a '99 NB that came with cruise control (but has since been removed from the engine bay) with a '94 bottom end, BP4W head, 6 speed swap, and still the stock 4.3 torsen (although I've got a 3.6 R&P I've yet to install). For engine management I'm running a MS2PNP from DIYAutoTune with only boost control coming out of the options port (Launch Control through the factory wiring harness). Prior to parking the car while I built the engine, flat foot shifting and launch control worked exactly as expected. After getting the car running on the new engine, I've tried a few different things to get it to work but to no avail. As of right now I have replaced the old clutch switch (the one at the top of the pedal, just to test the stock one with a multimeter and find it was still good), verified that the two neutral switch plugs are disconnected (at first I disconnected the reverse switch, but fixed that). I read that with the cruise control miatas you had to disconnect the neutral switch at the transmission, and I'm pretty confident that the two plugs I disconnected were the right ones but not 100%. The ones disconnected were the two white ones coming from the top of the trans.

Could this have something to do with removing the cruise control bits from the engine bay? Is there anything I could test with the multimeter to find out what exactly is wrong? I'd like to keep it operating through the factory harness, but I've considered using the options port instead. Oh, and I guess its worth mentioning that when the car was parked waiting for the new engines some rodents chewed through the reverse switch's wires but that has been addressed and there were no other visibly damaged wires, but I could've missed something. Dash was also removed to install a new carpet but everything on the interior still works so I don't think that would cause any issues. Either way with or without these connected it made no difference.

I've also verified that launch control is set up correctly (same settings as when it used to work), it is just not engaging. I've set it to activate using the "Launch" pin, tried anywhere from 1%-95% throttle at 1500-4000rpms with spark and/or fuel cut with retard to -5 to 9 degrees. I've tried to find somewhere in tunerstudio to monitor the input for the "Launch" pin but can't find anything, only outputs and the data that is used for fuel/spark calculations.

It sucked going to the drag strip and finding out I was faster with the stock motor with functioning launch control and flat-foot shifting @12-10 psi than with a built engine at 20-17.5 psi at 10-14 deg of timing without launch control and flat-foot shifting. I don't remember the time with the stock motor, but the built motor ran a mediocre mid 13s at 100mph flat. I figured if the MPH is slower (stock motor ran a 104mph), the time probably was too. After looking at the datalogs it takes as much as 600ms to come back up on full boost without flat-foot shifting, and since I've got the 6spd with the 4.3 I end up at the very top of 5th gear. 600ms of delay on full power x 4 shifts doesn't surprise me one bit that I'm going slower with 270whp than I was with 200-220whp. Any tips on where to start with diagnostics would be greatly appreciated before I try patching the factory harness into the options port of the ECU.

 

On a '99, the clutch switch goes to 3I. Disconnect the ECU, put a multimeter probe in 3I, connect the other to ground, and when you press the clutch, you should see continuity. On earlier cars, the clutch switch goes through the neutral switch as well, so both need to be activated for the ECU to see ground. But, according to the wiring diagrams, that doesn't appear to be the case for NBs such as yours.

 

Thanks for the tip/spoon-feeding lol. I took a gander at the wiring diagrams for a '99 and saw how after the clutch switch it is grounded at G202. I'm wondering if I somehow disconnected that ground while pulling the dash and forgot to reconnect it. I might try to take a look at it today if the weather permits it.

 

So… unexpected result here but everything checked out perfectly with the multimeter. First I checked the ground at the clutch switch switch and got continuity. Then I plugged the switch back in and tested it at the brown/white wire on the ECU connector. With the clutch not depressed I got no continuity, push in the clutch and I got continuity… Are there any fuses connected to the input that could’ve gone bad? I’m going to go take a look at all of the fuses and see if I find anything. When I get a chance later tonight I’ll upload a picture of my settings from the tune to double check that too.

 

So, I’ve removed the cruise control actuator from the engine bay prior to this. The 4 pin connector is currently open, nothing is connected. Everything else should still be there if I am remembering correctly. Could this prevent the launch control from working?

With the launch input pin seeming to work, wiring it into the options port doesn’t seem like it would help, so how does the stock system work? The wiring diagram shows a ground, the clutch switch, and then it splits off into the cruise control unit and the ECU. Of the ECU and the CCU, which one is the positive, or are they both positive and the switch grounds them both out? What I’m getting at here is how would I bypass the stock system?

Does the cruise control unit output a voltage, which normally goes into ECU unless the switch is grounded, and then it just takes the path of least resistance, effectively not inputting a voltage into the ECU?

Edit: I got the ol multimeter out and tested the voltage at the brown/white wire that goes into the ECU. With the cruise control switch in the off position I got no voltage. With it on, I got ~10v on the brown/white wire. Soooooo what I’m thinking is that the launch control might only work with the cruise control switch set to the on position. That is unless the ECU also outputs a voltage that gets grounded through the clutch switch. I need to go grab my laptop to re-enable the launch control to find out for sure though.

edit 2: nope no luck with the cruise control enabled. I guess the switch is a common ground and both are voltage outputs?

 

It’s just a ground input. You could do it with a paper clip. In fact the TEN/gnd jumper all the NA guys have to do for timing is just a ground input into the ECU.

 

Ok, so I've confirmed that the ground/switch/etc. are all good, it just won't engage. What should I do from here to address it? Should I just wire it to the options port since the LAUNCH pin doesn't want to work?

Also, huge thanks for helping me out here, it's not the first time you've helped me. I know how common these kinds of posts are, and I was afraid I'd just get ignored/no help.

 

Today, I figured I'd wire the launch control into the options port like shown


Unfortunately, this didn't work either. Do I have to move the jumper inside of the ECU to use the Launch input pin on the options port? DIYAutotune's wording is rather vague too so that's no help. From the DIYAutoTune website, "If you wish to disable using the clutch switch for launch control, you will need to take the lid off and remove the Launch via Clutch Switch jumper." Or does that just disable the stock wiring harness input and nothing more?

It is unclear if I need to do this to use other options ports too. I'm considering wiring it into the table switch input instead, but I'm not sure if all I have to do is just change the input pin in tunerstudio. I'm assuming the tableswitch input only needs to be grounded like the launch pin, or does it need a positive voltage?

Oh, also I opened up the ECU today and the Launch Control jumper pin is in the default position. Nothing seemed out of the ordinary either.

 

All digital inputs are ground inputs. There are a few exceptions, but not on the options port. Outputs are also all grounds, such as EBC, VICS, injectors, etc.

Are you trying all this with the engine running? For whatever reason, MS doesn’t display digital input statuses unless it’s running.

 

Ok, I think I'll try swapping the input pin to the tableswitch input next time I get some time. And yes, the engine is running and usually already up to temp. At this point I believe there's some sort of fault in my MS2PNP. Also, do you know where I can look at the digital inputs in tunerstudio? I've not been able to find them anywhere, just the outputs...

 

Unfortunately no, one of my many complaints about MS/TS. I don't like that they label them for you, like table switch, launch control, etc. I wish they were just 1-2-3-etc, and then in the software let you assign them to launch or map switch or whatever. After tuning hundreds of Megasquirts, this is one of the reasons I switched to Link, which does everything I mentioned and more. Simply press "R" while on PCLink allows you to look at the runtime values for everything. So a couple dozen fuel and ignition calculations, auxiliary outputs, PWM outputs, virtual outputs, digital inputs, analog inputs, and some other stuff. This all works even with the engine off, cause why shouldn't it?

As anyone can clearly see here, the clutch switch is active, and the transmission is in neutral, so neutral/park is active.


/link plug

GLWS.

 

With drag races coming up this next weekend, I’ve decided to try and get launch control working again. I’ve tried a few things but didn’t get anything to function correctly.

First thing I tried was rewiring the clutch switch into the Flex input port. This was a partial success in the sense that it got launch control to work, but the issue was that launch control was now on 100% of the time.

After this I removed the jumper within the ECU for the stock clutch switch to be used with launch control. Still using the flex input but now without the jumper, same results as before. Launch control is always on regardless of the clutch position.

Next I wired the clutch switch back into the launch input pin. With it wired in here and the jumper still removed, I got no launch control at all.

I genuinely don’t understand what could’ve changed. The launch control worked perfectly using the factory wiring harness before the car sat for a little over a year. Now it refuses to work at all. So infuriating having to keep messing with it and not getting any good results.

I’m about to start emailing DIYAutotune to see if they’ll take in the ECU to look at it themselves. Maybe some capacitor, resistor, or transistor randomly quit working. I genuinely have no idea what the issue is anymore. Any help would be greatly appreciated.

 

On my ‘99, nothing changed when I removed cruise control.

Tuner Studio has an annunciation that changes state
depending on the state of the clutch switch. So, you can know if MS is getting the correct signal in TS, without resorting to a multimeter.

Under Predefined Indicators 2 / Launch in, IIRC. At least on my MS3.

Maybe verify your TPS calibration?

Are you punching the gas pedal quickly?

Post your tune!

Are both Launch and FFS not working?

DNM

 

I've looked around for something to indicate the clutch position, but haven't been able to find anything. Only the "Launch" indicator at the bottom of the dashboard. After searching for "predefined", "indicators", etc at the top right search bar, I've not been able to find anything on tunerstudio other than something about timing wheel decoding. Under which tab are these predefined indicators at? I am on a MS2PNP if that matters.

TPS is calibrated. 0% +/- 1% when closed and ~100% when fully opened.
Punching the gas/holding doesn't make a difference. I've tried both.
Tune is attached.
I've always used only Launch Control with rpms set around 4000rpms or so. Never messed with the flat-foot settings since just launch control gives me the same results. I guess I shift quick enough for it to not matter.

Also, when this was working I'd set the TPS to 95% so it doesn't accidentally enable while downshifting. The settings show are just what I was using to test without making too much noise. I've tried both fuel cut, spark cut, and both.

Tune attached, but here's a screenshot too.

 

That "Launch" may be all you have, and that may be when launch is actually active. MS3 has 2 separate launch related annunciators.

MS3 also other features, such as no launch if speed > XX, which helps with not going into launch during shifts.

Have you tired normal settings of Hard limit = 4000, and TPS at around 30 or 40?

MS3 >> MS2

DNM

 

I just got back from messing with the VE table some more. Took a lot of fuel out in the higher rpm/med load areas. Smoothed the table out a bunch more too.

Anyways, MS2 does have launch and flat-shift, I just never cared much since it works how I want it to as I never raised launch above 4500 or so. I want a better ECU but I'm debating jumping into the deep end with a haltech if I get something better. Should've just gone with MS3 to start, but I went with MS2 thinking the only benefit would be the ability to run E85 on MS3 and I don't have access to E85 where I live. Now that I'm more informed I realize that MS3's Accel Enrichment and things like VSS make things a lot better. I also really enjoy tuning and messing with things so learning the haltech platform is interesting to me.

I've tried normal settings too, no luck there. When I had the clutch switch wired to the Table Switch input, launch was always on and it would engage at 1% TPS and 2500 rpms, so I don't think the thresholds are the issue.

 

I had to put a switch in-line with one of the transmission switches. It is two position. One leaves it as factory the other night ground it or ???. I’d have to check. When I toggle the switch LC and flat work as they should. It must be in the neutral switch since the other is reverse.

Factory wired LC would not work. It kind of was an artificial rev limiter at all times before I added a switch.

 

I need to double check that I still have it disconnected. I know I did at one point, but now that I think about it, I may have reconnected it since the launch input pin didn't work either way. When I was trying to get the table switch input to work, it is possible that it is working as intended, but the neutral switch is still connected like you mention. Fingers crossed that this could be the issue. I will check today after work. I've got ~54 hours until the drag race, and I'm not too optimistic about the results without launch control working. I'll try to update with my findings tonight.

 

So I checked, and the neutral switch is still disconnected.

While I was at it I completely disconnected the clutch and tested the launch control with the TableSwitch input. With nothing at all connected to it, the ECU still activated launch control. It has to be an internal fault in the ECU.

I’d happily ship it to DIYAutotune and pay for repair but those ******** won’t even answer my email. I’ve emailed them 3 times now over a week. The most recent email was right before typing this out. Just thought it was funny because in regard to emailing them for tech support they claim “We’re very good and fast at it. Please give us a chance to prove that.” Funny. Probably will just buy a BMM ECU at MATG to support them and the community rather than the cash grab called DIYAutotune /end rant

 

I finally ended up getting Launch Control working. While we couldn't figure it out using the launch input pin or the factory wiring harness, I was able to get it working with the tableswitch input. After DIYAutotune finally replied they informed me that the AC Idle Up jumper inside the ECU needed to be removed from the Table Switch pin to use the Table Switch input pin as the Launch Control input. After doing this everything finally was working. Unfortunately, the drag races I was planning for were canceled due to rain. I guess my MS2 lives to see another day.