Speedo not working after a Mitsubishi head unit install?

[dimi_108]

Hey fellas,
Weirdest thing happened today. Because i'm kind of sick listening to AM radio and anything under 90.0 i decided to install an OEM head unit from a 2002 Mitsubishi Verada for now. Anyway, head unit worked great and sounded good but i NOTICED my speedometer totally not working and just sitting on 0km/h. Everything else on the dash worked. Fuel, tacho and temp was functional but just the speedo didn't move. I plugged in the factory Legnum head unit again and then the speedo was back to normal?

Anyone got any idea what's going on there?
The plugs go straight in to the Mitsubishi Verada head unit, no modification or new harness was needed

 

[SiliconAngel]

Freaken heck that's weird. There's a speed signal wire to the back of the dash cluster that controls your gauge, there shouldn't be anything between it and the sensor, which splits off to the ECU as well (but the ECU and the gauge don't communicate). There shouldn't be any connection to the head unit that I'm aware of...

Brad and Carsten, ever heard of anything like this?

 

[Guest]

you've wired something up to the speed sense wire, i'm not 100% of the colour on the loom, but mine came with a few adaptors for the factory sat nav, and it was a green wire.

if you attach something to it, the speedo will sit on 0, but everything else will be fine.

it's used to shut off MMCS/etc. above a certain speed.


edit: found my loom adaptor.
ok, the speed wire is the on the bottom row, third from the right. on my adaptor it is a green wire, but i'm 99% sure the car loom it will be a white/blue wire, its is definately third from the right on the bottom row though.

this picture is showing the 'car' loom coming from the bottom right, and the extension to the deck coming towards the camera.

 

[bradc]

I'm pretty sure Mitch has answered it there!

I'm willing to bet that the Magna wouldn't have had speed cut from factory, and I'm also willing to bet that if you chose to test it out in your VR-4 that you would be able to pass 180kmh now as well

 

[dimi_108]

Thanks you three for the explanation and advice
Brad, so the speed wire is the green one closest to the camera? Should i snip it?

The head unit is the one shown on the top. I relocated the old head unit to the bottom.
If i cut the green wire, will that bring the speedo to life again?

 

[SiliconAngel]

Dimi from what I understand, there are two wires from the sensor, one that goes to the gauge and one to the ECU. If you cut the one to the ECU that removes the 180km/h speed cut and I believe speed information for MUT-II diagnostics (ie EvoScan), but it shouldn't affect the signal to the gauge. However this is just information I have gleaned from reading stuff on CVR4 - I don't know about the pass-through plugs specifically, but I assume what's happening is that plug that you've connected to your deck is plugging the ECU speed sensor wire into an active pin on the deck (as Mitch said), which is pushing a feedback signal down to the sensor which is confusing it and the gauge.

It'd be interesting to cut that wire and see if it affects speed cut or MUT-II diagnostics, or if it's a third cable from the speed sensor that doesn't actually serve any purpose...

 

[ygoslo]

On a related note, when I installed my H/U yesterday we found that at max volume watching a DVD with the engine off the speedo needle went up and down with the sound!!! No idea why, but it doesn't seem to do it anymore...

 

[dimi_108]

Thanks Trev for further explaining it.
Would the same problem with the speedo happen if i were to install, say, an aftermarket head unit? Like a Nakamichi etc.? Or is this most likely happening because the head unit is from a Magna without speed cut?

 

[SiliconAngel]

Well if it were my car I can guarantee I'd never even see your problem - because I'd be running new cables for everything; I never use the factory loom for stereos. Aftermarket head units won't take the factory loom connector, so you'll be forced to cut and join the wires you need and you won't bother with anything else (such as the speed sensor wire).

 

[Chris Rogers]

speed dependent volume - find the speed wire on the radio plug and snip it. post a shot of the plug and I'll help you.

 

[dimi_108]

Thanks Chris. Any help would be really appreciated.

The first photo is showing the pins:

Second photo is the plug on top:

Third photo is the plug underneath:

Fourth photo is a bit closer. Hope you can see what is what:

 

[Chris Rogers]

show me the back of the plug. I think I can see your problem but need to see the wire UNDER the wht/blk one. I can see the front/rear speakers and the lights/pwr ant but I cannot see the other one.

show me a BIG image of it.

 

[Chris Rogers]

so did it get fixed??

 

[dimi_108]

Chris, you're a genius mate thank you.
I did what you said and snipped the wire that was under the white and black one. I've got my speedo back - and best of all, the new factory head unit working

 

[Chris Rogers]

one thing ti bear in mind with that - the left front speaker shares the same colour wire. note that when snipping wires.

speed dependent volume is on a lot of cars. Opel use a similar concept on the astra,vectra etc. when you swap units on those cars the same thing occurs.

glad to see I was of help and you learned something in the process

 

[Maweu]

Facing this problem now.

 

[Maweu]

Thanks Chris. Any help would be really appreciated.

The first photo is showing the pins:

View attachment 51066

Second photo is the plug on top:

View attachment 51067

Third photo is the plug underneath:

View attachment 51068

Fourth photo is a bit closer. Hope you can see what is what:

View attachment 51069

Would you please post these fotos again

 

[tsai1]

Yes I could really use the pics as well

 

[BCX]

Speedo wire at the headunit is white/blue.