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lewis

DASH2Pro RPM Help

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lewis

I'm having some trouble with my DASH2Pro RPM readout. I know it used to work when I first fired up the MX-5 engine to test the wiring.

 

Now the wiring is in the car the RPM doesn't work at all. The way the tacho signal comes is there is a black/white wire coming from each of the two coils which merge into one wire. Then it splits back into two, with one going to a pin on the ECU and the other to drive the tacho. When ignition 2 and the engine is running around 12v is being output on the wire to the tacho, however when I connect this to the DASH 2Pro low RPM input (yellow wire on connector B) the signal drops to around 6v and no RPM is displayed. I've even disconnected all other wires from the DASH2 so its just power and RPM.

 

Connecting the original Mazda dash back up shows the RPM working and the tacho wire staying at 12v.

 

Its a post 1994 1.8 MX-5 engine with a 4 pin coil.

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TableLeg

Are you able to view the Rpm via the ECU?

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lewis

Not that I know off, at least on the stock Mazda ECU.

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TableLeg

Ahh right sorry Lewis I didn't realise you were using the stock ecu.

 

Does everything else work on the Dash2?

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lewis

It seems to. The fuel gauge and temp and pressures pick up a signal. Wheel speed might not work but haven't got that far yet. Also all the warning lights and switches work OK.

 

Here is the Mazda wiring diagram

image.png

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TableLeg

Do your coilpacks have 3 or 4 wires? If 4, are you certain both coils have the Blk/Whi wires populated?

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lewis

Yep, definitely 4 wire on the coil pack and connectors.

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TableLeg

Have you checked the diagnostic connector rpm wire as well?

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TableLeg

The reason i asked about the coils as it appears that despite the loom having 4 wires on some MX5's the actual coil does not have the rpm connector pin in it. Pulling off the plug connector and looking inside can reveal on some only 3 pins in the connector.

 

See here

http://www.mx5nutz.com/forum/index.php?showtopic=94140

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lewis

Yeah, seen the earlier 3 pin ones. All signs say I have the 4 pin coil and plug and wiring.

I decimate never had an igniter which the earlier mazda's used.

The diagnostic port reveals the same voltages on IG- and GND pins as the tach wore on the loom.

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TableLeg

Does the tacho output a pulse or give a steady 12v?

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lewis

On my multimeter it looks like it's a steady voltage but it is a pulse. Twice per revolution I belive.

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TableLeg

Strange then, it would seem that if you output is correct on the tacho wire (which it appears to be) then maybe the issue lies with the Dash2.

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lewis

It looks like it could be that, I really hope it's not though. I've emailed their support about it too.

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TableLeg

I hope you get an answer from them soon, in the meantime hopefully someone more knowledgeable may be able to offer some suggestions.

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