Getting the speedo working isn't the problem. Getting the ECM to read VSS so it can set OBDII readiness is.

In plain language - the Automatic has a TCM embeded in the transmission. It's writing the VSS speed to the ECM via canbus. With the manual transmission, the ECM is reading the transmission pulses from the VSS sensor. I believe that because my ECM is from an automatic, it lacks the programming to read the VSS pulses.

I think the sensor for a speedometer for a manual transmission was in the hub at least it was for my 99 vette. When you changed rear gears the speedometer was unaffected.

My plan was to use and GPS sensor for the speedometer and the Dakota Dash convertor. I hadn't researched far enough to see what the ouput of the GPS was , but I would guess it is a pulse.

Dakota sells a tunable pulse input speedo. I was looking into them recently.

The next person that mentions a product to drive a speedometer gets the hose. Y'all missing the point.

I did a bit more reading last night about flashing the ECM - E39a ECM's are reflashable via J2534 interfaces that can be had for about $40 (Hurrah for congress - 2004 law states manufacturers can't lock out independent mechanics) - much more palatable than your $1000 TechII scanner or $1500 GM MDI interface. You can also buy a 3-day trial to GM GDS2 (Global Diagnostics System v2) for $57, which gives access to tis2web (repository of the various firmwares).

However - it looks like nearly everything is based off the VIN. Doesn't look like you get to pick and choose the modules (unless they have a associated TSB for corner cases).

I've also run across some annoying news about GM's "Global A" program - under the purpose of preventing the reselling of stolen car parts, modules are encrypted to prevent interoperability in a different car. The article I read was lacking a lot of detail - but remember those stereo's that wouldn't work unless you had a special code? Imagine that, but for a fuel pump control module. Or transmission module. Or ABS controller.

Aside from that annoyance, which I don't think I have to contend with unless the ABS controller somehow uses the wheel speed sensor on conjunction with the driveshaft sensor for traction control and vehicle speed - I think I have plan(s) of action - my 3 options are..

A. Take ECM to dealer for reflash - ($110). Get laughed at when they say they won't do a standalone flash. Get laughed at more when I show up in a Mazda and ask them to reflash. Assuming they'll do it (which I'm doubting - never trust a service manager) I'll probably need to provide a VIN from a manual transmission'd car to get the bits I want, which'll mean using 2 more credits on HPTuners ($100). $210 total.
B. Snag a J2534 controller, flash it myself ($90). Program for another VIN. HPTuners ($100) again. $190 total.
C. Grab another ECM ($50 - $150). HPTuners ($100). $150 - $250 total. Upside - I have 2 ECU's.

C seems most palatable. I'm off to make some phone calls.

Edit: Phone calls complete. I've got a '14 ECM from a manual coming my way for $65.

How did V8 roadsters get around it? They used a different fuel pump with a manual regulator and tuned around the pressure changes. What does it need for the transmission if its a manual? Also, did their ABS just not work?

I'm a gm tech all our reflashes are based on what vin the mdi reads. Basically it reads the vin then the service programming system (sps) decides what calibrations are available. Only thing you can really select is for older calibrations or there might be certain calibrations available based on the rpo code. Now it is possible to manually input the vin into sps (Ive done this once or twice when installing a junkyard ecu) but your still stuck with only the calibrations available for that vin.

Did the automatic car have a tcm? If it did the ecm is expecting to receive the speed signal from the tcm over the high speed data bus.

Thanks for the verification - :likecat: - I figured there's also hoops to jump through to have a dealership reflash to a different VIN. Engine (and harness) originally came from an auto with a TCM that's long gone. I've stripped the automatic wires out and added VSS wires to the Replicated TOS inputs on the ECM.

Hopefully it'll all work out when we get the car back next week.

ABS is still a Mazda module, no tie in with the GM stuff. And - again - I hope with the new ECM all this VSS stuff just starts working.

Forgive my ignorance. Trying to get a grasp of what you are trying to accomplish. VSS, Vehicle Speed Sensor - you're saying the ECM needs this signal? What happens without it? Does the engine shut off or does it reed it to change the tune? The previous generation of LS engine only needed it for an automatic transmission (gear changes).

Judging by his comments regarding the "OBD-readiness" condition, it will throw a CEL. Which in turn, will not allow the car to pass emissions as the Miata chassis is an OBD2 VIN. No emissions pass on OBD2 car in GA (county dependent) = No registration.

According to gm service information that 14 ecm has two possible vss pin outs depending on what rpo the trans was.

I put in a call to v8roadsters and got some more info. Long story short - I made an assumption.

There's 2 versions of the ECM - the E39 and E39a. E39a, on top of having this VSS issue I'm seeing also requires the body module to control the alternator. This could be worked around fairly easily by using a standalone circuit to control the alternator (similar to what megasquirt does with NB's with PWM) instead of the ECM.

But my E39a VSS issue - if I had some time with a V6 Camaro I might could figure it out. My guess is there's communication between the ABS wheel speed sensors and the ECM/TCM for StabiliTrak.

Which is silly. In HP Tuners you just just turn the related codes off and it'll autopass the readyness monitor and wont light the CEL. Of course that is for offroad use only.

Is there any specific wiring diagrams or connector pinouts you need? Also if you have a vin # I can pull up what rpo codes that vehicle was equipped with.

I always forget HP Tuner's integration with this situation, and how compatible it is with emissions laws. Doh, you are correct, I remember this now from a buddy's Colorado he had tuned on HP Tuners, it was nice to just "turn shit off".

Finally set out to build my cluster today. This is a SpeedHut gauge set inserted into the OEM cluster. Pretty pleased with the outcome and not too hard to do. If anyone wants a write up I will be happy to do one.


https://www.miataturbo.net/attachmen...ine=1459028240


SpeedHut gauge set in the OEM cluster.

Yes please do!

Some encouragement for you guys:


Ran the car yeaterday at the DC SCCA test and tune autox. Car ran great, no issues whatsoever with over 30 runs. Throttle is very sensitive and very easy to pick up too much speed even on 205 series R compounds. Next task is going to be to step up to 275s.

Sounded awesome from outside the car. I'm running a tein monoflex suspension and Re-71r's, the same as last year, and there's no noticable change in the handling characteristics other than than lots more power. Still very nuetral, very balanced. All in, super happy with the swap.

What are running for an exhaust? Dual 2.25 into a single 3?

Gooflophaze, If you need a hand pulling signals let me know. I can probably find a v6 Camaro to go rent. I don't have a data analyzer, but I do have a four channel digital O-scope.

Thanks for the offer Cujoel and B6Tfastiva - for the moment, I think I've got everything (well, everything except for an E39 ECM - that'll be my priority this week). I may loop back around to get the E39a working at a later date.

Tow vehicle decided to be a punk when the exhaust was finished on Friday. Thought it was the batteries, hooked up the charger, no joy, took them to autozone, tested, nope they're fine. Googled for why it wasn't cranking - oh, those ignition switches are known to be a PITA. By the time we swapped it out it was late on a Friday before a holiday weekend.

Today, cranked the diesel back up - since its resurrection the fuel gauge has been kaput - went to fill it and reset the odometer - and proceeded to get stuck in the gas station for an hour. Finally smacked the starter the right way and retrieved the miata. Just let the truck idle the entire time.

https://www.miataturbo.net/attachmen...ine=1459206442

2.25 y'd into 2.5 with (I think) a 3in resonator.

I took a video of the exhaust and a couple of free revs, but my cellphone doesn't do it justice. I'll need to break out the gopro.

Yup, 2.25s into a single 3 with a magnaflow muffler - i just modified Enthuzas single LS exhaust to fit. Jason sent it with everything in front of the Y unwelded and it worked great. It's starting to break in well, seems like less rasp.