Did my megasquirt2 die?!

[E30Bastard]

I just bought a mspnp2 and wasted spark setup from diyautotune. Everything installed easily and I had the car running in a couple days.

Was adjusting my VE table for op temp idle and the car just shut off. I tried turning it back on and no go. Also, I found that I could no longer access the megasquirt via tunerstudio. I did some electrical testing, the harness gets 12 volts on pin 36. The switched ignition wire (green wire that used to go to coil) no longer gets 12 volts. I have no shorts (tested all the new wires I ran for the megasquirt and I also tested old wires in the harness relevant to computer and ignition). There are no blown fuses - I've checked them all with a voltmeter.

The only physical change I made was changing the jumpers from sequential to wasted spark.

Did my megasquirt self-destruct or am I just annoyed and missing something stupid? The only thing I haven't done is bench it but seems pointless given that the harness tests out perfectly.

Thanks for any insight.

[2mAn]

You’re missing something stupid... it’s something stupid

[E30Bastard]

I should specifically add that I tested harness pin 27/coil wire and it fully checks out. I also tested IAT and it is getting .8 volts...

[ForcedFirebird]

What about 5v signals? The MS uses 5v to communicate with the PC. I had a 5v regulator go bad in an MS box one time, had very similar symptoms.

[E30Bastard]

Hi Firebired,

Thanks for the response. Just finished another series of diagnostics. LED 1 and 2 are not on (as I am sure you know, these are the 5v and 12v indicators). Also, I don't get 5v out of pin 5 and 12v out of pin 23, which are the correct pins for the options port. For that matter I don't get voltage to anything that should be coming from the ms2.

I have also removed the ms2 and benched it with 12v to pin 36 and ground to pin 2. It does not light up out of the car as well.

I am mystified. The car was idling perfectly and I was standing at my laptop. No electrical smoke anywhere, no burning smell, no blown fuses or relays. I just tested the main relay even though it's only a year old and these things usually need a short to go bad in California. Everything checks out, I am not sure what else I could test.

One question I have, and I am certain of the answer but I want to confirm for my own peace of mind -

the pull-up jumpers next to the wasted spark jumpers need to remain plugged in, correct?

I am going to open up the MS2 and look for a fuse. I doubt one exists. (*EDIT - No fuse or circuitry protection in the ms2?! What?!?! I am going to attach a picture below.)

[E30Bastard]

Mystified.

[E30Bastard]

And here is proof that the pull up jumpers were, indeed, correctly installed:

[E30Bastard]

All right 4 weeks later, I received my MSPNP2 back from RMA in the post on Friday. I plugged it into my car's harness and it did not power up. I've tried giving 12v to pin 36 and a solid ground to pin 2 but the unit does not turn on. I want to verify that pins 36 and 2 are what I need to bench this unit. DIYAutoTune said that the unit powered up and that they were able to access TunerStudio but I cannot get this thing to turn on for the life of me. The status LEDs are off in or out of the car. Very frustrating.

*edit* Other than needing to just get my ECU to turn on it's pretty clear that the green ignition coil wire (the switched 12v I was using for the coil packs) was the reason why the car turned off mid-idle as this wire no longer gets 12v. The ECU pinout lists pin 27 as "start input - to ignition switch and coil". Please look at my attachments. Any ideas as to why this wire died on me? I've run continuity tests from green coil wire to pin 27 and everything checks out.

[ForcedFirebird]

Seeing they were able to connect, have you troubleshooted your PC and/or cables (or tried others?)? I had a couple instances where the rs232/USB chipset died in the cable. One time was racking my brain and after bothering Nando while trying to bench flash an MS41.1 - sure enough, his hunch was right, new cable and all was back to normal.

[McGyver]

All right 4 weeks later, I received my MSPNP2 back from RMA in the post on Friday. I plugged it into my car's harness and it did not power up. I've tried giving 12v to pin 36 and a solid ground to pin 2 but the unit does not turn on. I want to verify that pins 36 and 2 are what I need to bench this unit. DIYAutoTune said that the unit powered up and that they were able to access TunerStudio but I cannot get this thing to turn on for the life of me. The status LEDs are off in or out of the car. Very frustrating.

I would start by verifying that I could get you PnP to turn on. I'm not sure where you bought yours, so I don't know how it's wired to get power. This list indicates that you 12v IN should be on the 55-Pin Number 37 and ground on Pin 2:
https://www.diyautotune.com/support/...-1992-bmw-325/

Pin 36 supplies a ground to trigger the main relay. Pin 37 is the power input from the main relay. More info and explinations here:

https://www.r3vlimited.com/board/forum/e30-technical-forums/engine-drivetrain/alternative-tuning-w-a-r-megasquirt-etc/9917593-megasquirt2-v3-0-w-ms2-extra-3-4-2-build-and-wiring

Once it turns on, check it with tuner studio too verify your cables are good. Then check your car's harness to make sure you have power/ground where you need it.

[E30Bastard]

Thanks, McGyver. You are the man.

Progress. I got the ECU to fire up outside of the car following your directions. I then traced out pin 37 to the main relay via the bmw wiring/troubleshooting guide. Main relay has two pins that are hot at all times and both these pins test out good. I also tested motronic pin 37 to main relay receptacle and that wire tested out good as well. Motronic pin 36 gets a constant 12v with the main relay plugged in. Jumped 12v to motronic pin 37 and the ECU turned on inside of the car. I have a couple spares of that main relay, used parts from other cars, and I tried them both with no change in behavior so I don't think the main relay has died. Ignition was recently replaced in 2019 as well.

Not sure what could be keeping 12v from hitting motronic pin 37 when the key is turned as the wire tests out great. Per your earlier post, if I am understanding this correctly, ECU shorts pin 36 and that triggers the main relay to supply power to pin 37. What tells the ecu to short pin 36?

[E30Bastard]

If this isn't a typo in the information attached below it looks like the main relay needs to give 12v to motronic pin 26 (this pin is listed as AFM common, ground pin 4) in order for pin 36 to be shorted, cause the relay to latch, and finally pin 37 to be energized. Not sure how an air fuel meter wire would be involved in the ignition process though. I did test pin 26 with the ignition on and there is no 12v.

In short - ignition on, ecu pin gets 12v from main relay, ecu shorts out pin 36 which in turn causes relay to latch and supply 12v to pin 37.

How/why to pin 26? And if this is not a typo how does an AFM cable tie into ignition sequence, especially if it was unplugged and running fine without it. It has to be a typo?! *Edit* I tested pin 26 to AFM ground 4. Wire is perfect but still don't understand why it would have anything to do with the process described in the below screenshot.

Check this out:

[E30Bastard]

All right. It's a definitively a typo. Pin 27 is what should be getting 12v to tell the ECU to ground pin 36, which in turn energizes pin 37 at the main relay.

So this explains why I'm not getting 12v at the green ignition coil wire either. This is all definitely related to the one cause. The wire from the coil to the ECU checks out. I'll have to check out the diagrams if I get a few minutes at work today. I know pin 27 is energized by the ignition but are there any junctions under the dash? Any leads on pin 27 wire path would be awesome.

And just from my memory what is the mysterious "Fusible Link A", by the battery leading directly to the fuel pump relay? The reason I ask being that the fuel pump relay is also energized by main relay pin 87 (same pin which energizes motronic pin 37 as well) so maybe there's something happening there. Just some morning thoughts. I'll have to search for the fusible link A diagram later in the day. The instant death of my car mid-idle is explained (no voltage at pin 27), now must find the cause.

[JehTehsus]

All right. It's a definitively a typo. Pin 27 is what should be getting 12v to tell the ECU to ground pin 36, which in turn energizes pin 37 at the main relay.

So this explains why I'm not getting 12v at the green ignition coil wire either. This is all definitely related to the one cause. The wire from the coil to the ECU checks out. I'll have to check out the diagrams if I get a few minutes at work today. I know pin 27 is energized by the ignition but are there any junctions under the dash? Any leads on pin 27 wire path would be awesome.

And just from my memory what is the mysterious "Fusible Link A", by the battery leading directly to the fuel pump relay? The reason I ask being that the fuel pump relay is also energized by main relay pin 87 (same pin which energizes motronic pin 37 as well) so maybe there's something happening there. Just some morning thoughts. I'll have to search for the fusible link A diagram later in the day. The instant death of my car mid-idle is explained (no voltage at pin 27), now must find the cause.

I believe with the PNP (I built a wasted spark MS2 harness and completely custom 3 harness recently where I rewired the main relay, but I am somewhat familiar with what has been done on it for the PNP and for the factory setup) they use a transistor circuit that provides ground to the control side of the main relay, which switches (almost) everything in the engine bay on, or at least provides power so it can be switched on. This transistor is turned on when the key is turned to run and small green ignition/switched power wire, coming from C101 pin 7 at the ECU has 12V, and once turned on the main relay should be switched on as well.

I would recommend checking that C101 wire - verifying with the key on and C101 unplugged that you see 12V on pin 7 of the connector, on the car side. If that is true, check the wire on both ends of the engine harness (i.e. c101 pin 7 and ECU connector pin 27), which if you have a break it is likely to be somewhere in there. If you have no power on the C101 car side it could be a bad ignition switch, but you should be able to tell because other things inside won't light up.

Don't stress too much about the fusible link, it is a piece of wire in the trunk on cars with trunk mounted batteries that burns open before the entire wire and car catches on fire. If you burned it you would easily be able to tell by checking whether the big wire that comes into the engine bay from the trunk (+ post) has 12V or not when the battery is connected.

[E30Bastard]

Thanks!! This is great diagnostic info. Will follow the steps you described. I checked for 12v at the post under the engine bay previously but will double check again tonight and cross any potential issues out there.

Take a look at this explanation of the wire route. Interested in this "two pin socket above the glovebox, fitted with a plug and a loop (where the immobiliser should have been connected)" as well. What is the immobiliser? The harness has been manipulated to adjust to the new ECU so maybe there's a break at this two pin socket as well.

*Edit - I'm not sure this site is very accurate. They had pin 26 listed instead of pin 27 and in this attachment pin 20 listed instead of pin 7, as you described.