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Old 09-09-2016, 06:27 AM   #1
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Default White Wire Ground Block (JC-01) 4x ECU 1x ?

As I seem to be having wiring problems. So I thought I would ask.

The white grounding block (JC-01) on the passanger side (Drivers side for USA) has 5 wires.

I'm assuming 4 of them wires go directly to the ECU and don't bridge into anything else. But where does the 5th wire go to?

Reason I ask is my left headlight died and wouldn't do full beam even after testing the blub. I wiggled the wires coming out of the ground block and it came alive. So I'm assuming it's in relation this this wire and that it gives ground to the left hand side of the car?

This could also be in relation due fueling going mad and TPS jumping around due to a broken / crappy ground.

If the ECU goes direction to this block I will run 4 new wires to rule them out.

Thanks




EDIT *** After looking at a few wiring diagrams. I am wrong in what I said.

2x ECU main ground
1x ECU sensor ground (This has 2 wires from ECU thats going in one wire)
1x Fuel Pump Switch / TPS / O2 Sensor / Coolant Sensor ground
1x ?


Please do correct me if I'm wrong.



Miata mk1 1990 1.6 - MS2e

Last edited by Lawone; 09-09-2016 at 09:16 AM.
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Old 09-09-2016, 07:47 AM   #2
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What year miata? What ECU?
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Old 09-09-2016, 09:15 AM   #3
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What year miata? What ECU?
Well that would bloody help wouldn't it :S


mk1 1990 1.6 on MS2e
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Old 09-09-2016, 09:32 AM   #4
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Yeah, poor grounding can cause all sorts of issues. Your headlights ground directly to that connector so makes sense fixing a loose connection made it come to life.

But your sensor grounds are on a different wiring.

I honestly think there would be service in removing all sensor grounds (Black/LTGreen), removing them from the chassis, and sending those back directly to the MS, before simply "adding grounds" for the MS.

On the ECU harness there's two main grounds (black) and two sensor grounds (black/green). If you look on your wiring diagrams for the AFM you can see this clearly -- the AFM, Thermistor, CLT, AIT, etc, all ground back directly to the ECU via 2C and 2D -- problem is that they also connect at the fuel rail so it kinda defeats the point of grounding at the ECU as opposed to the chassis.


Since you have a noisy TPS, I'm assuming you've added the vTPS. TPS sensor can just be inherently noisy -- one thing you may want to do is adjust the vTPS so it's not at full stop when at 0% throttle. You'll need to recalibrate the TPS in Tuner Studio.

Fueling could just be bad tuning. Would help if you posted logs and a tune file to help any further.


What exact MS2 unit do you have? A diypnp? v3.0? MSPNP? MS Labs MS2e?
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Old 09-09-2016, 11:16 AM   #5
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Originally Posted by Braineack View Post
Yeah, poor grounding can cause all sorts of issues. Your headlights ground directly to that connector so makes sense fixing a loose connection made it come to life.

But your sensor grounds are on a different wiring.

I honestly think there would be service in removing all sensor grounds (Black/LTGreen), removing them from the chassis, and sending those back directly to the MS, before simply "adding grounds" for the MS.

On the ECU harness there's two main grounds (black) and two sensor grounds (black/green). If you look on your wiring diagrams for the AFM you can see this clearly -- the AFM, Thermistor, CLT, AIT, etc, all ground back directly to the ECU via 2C and 2D -- problem is that they also connect at the fuel rail so it kinda defeats the point of grounding at the ECU as opposed to the chassis.


Since you have a noisy TPS, I'm assuming you've added the vTPS. TPS sensor can just be inherently noisy -- one thing you may want to do is adjust the vTPS so it's not at full stop when at 0% throttle. You'll need to recalibrate the TPS in Tuner Studio.

Fueling could just be bad tuning. Would help if you posted logs and a tune file to help any further.


What exact MS2 unit do you have? A diypnp? v3.0? MSPNP? MS Labs MS2e?
Thank you.

MSLABS MS2e

I've removed the Black/green cable from the inlet side. This is the one I found that went too a little spade connector in the inlet manifold itself.
I also have;
2x Black wires
1x COP extra ground wire
1x wire to bulkhead ground

going to a camcover bolt.

So.. from what I understand it would be very worth while to remove the 2C & 2D from the white tab connector and wire directly to the ground cables that feeds as you mentioned above the AFM, Thermistor, CLT, AIT, etc to prevent any unwanted noise.

So for the best setup

2A & 2B are the main ECU grounds and anything that uses the 2C & 2D (sensors) go directly to 2C & 2D cable without touching the chassis or engine block at all? to give MS2e the best signal possible.

In regards to fueling problem. I totally forgot it's due to the vTPS. going mad and turning on acceleration enrichment. So the ground wire is foo barred and cauing mayhem. As when I wiggle the wires next to the white grounding block it's okay.. :S

Last edited by Lawone; 09-09-2016 at 11:30 AM.
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