Can someone please tell me what that plug is for?

[acjx880]

I have had an aftermarket alarm system and head unit installed when I bought my BH last year from a local shop, and last weekend when I was installing my foglights and the DIY: Brighton Tach posted on this site, I noticed these green plugs not connected:
https://sl-i.net/FORUM/images/imported/2007/04/Image004-2.jpg

Assuming that the plug has been disconnected either by my alarm guy, or the dealership who replaced my front MAS since last December, the car has been running fine. When I did connect these green plugs and start the car the CEL would blink constantly. Thus I was hoping if someone could tell me what that plug is for.

Also after I've installed the new tach I bought from AllSubaru.com, I've noticed that the rev displayed is incorrect as I don't think the engine rev should only be just above 2000 rpm when I'm doing 140 KM/H (80 mph)!

I'm waiting for my friend to get off work tonight and bring the car over to his place to use his reader to get a code for the CEL, but any pointers in the mean time would be much appreciated.

[Wiscon_Mark]

Yeah, it beeps a lot.

That's for techs to reset the ECU without taking the battery out. And presumably to run diagnostics.

[d1giPhux]

I'm pretty sure i have those on my car doing the same thing as well.

[Huffer]

When they are connected the car enters a diagnostic mode.
They are supposed to be disconnected.

Edit.

On cars overseas, there is no OBDII standard, so the readers are not heavily used. When a CEL is triggered, most owners take it into the dealership or attempt to connect the plugs with the intent of reading the code.

The number of flashes on the CEL indicates the error code, usually.

[Khanhfucious]

Those are diagnostic plugs. They plug those together to reflasht he ECU among other things.

[Plays_with_Toys]

At 70mph in 5th gear in my car is 3000 rpm's. I know because above that and my car droned with the old exhaust, so I kept it there for road trips.

[Wiscon_Mark]

At 70mph in 5th gear in my car is 3000 rpm's. I know because above that and my car droned with the old exhaust, so I kept it there for road trips.

huh?

[Plays_with_Toys]

Also after I've installed the new tach I bought from AllSubaru.com, I've noticed that the rev displayed is incorrect as I don't think the engine rev should only be just above 2000 rpm when I'm doing 140 KM/H (80 mph)!

[acjx880]

Alright, I was thinking that it was for something else, maybe even causing my tach to be inaccurate...

Thanks guys!

I also did a little test on the tach again while I was out earlier; I held the car in 2nd gear and accelerated till tha gas was cut-off: the gas cut-off was just past 4000 rpm. I've driven my gf's Legacy Outback and I remember I got it to rev past 6000 rpm under hard acceleration. Could it be a faulty tach that I got, or is there something else I need to check?

[Huffer]

Sounds like your car is in limp mode.
Try a cold reset - unplug the connectors and unplug the battery.

[Wiscon_Mark]

No, it sounds like his tach is completely off - 80mph and 2000 rpms?

[Huffer]

Dunno. I read his last post - 2nd gear until fuel cut = 4000rpm...

maybe the needle isn't sitting on the spindle right...

[Plays_with_Toys]

Did it sound like only 4000 rpm's or was it really rapping out the motor?

[acjx880]

No, it sounded like it really was rapping out the motor, also the needle only sits at 200-250 rpm (1st mark above the zero) once the car is warm...

Even if I floored the gas pedal, the car shifts at about 3000 rpm, and at 4000 rpm the engine sounds like it should be at 6000 rpm. I know this because I used to drive an Integra Type-R for 6 years which I would rev it up the 8000 redline on a daily basis. =P So I'm pretty sure the tach is off, but just don't know how to fix/adjust it. Even when I took it back to the dealer for tranny and diff fluid change today, the tech said it was ok, but when I told him that the cut-off was at 4000 rpm , he just said maybe its because I installed the tach myself and couldn't give any other explanations.

[Wiscon_Mark]

...he just said maybe its because I installed the tach myself and couldn't give any other explanations.

:roll:

Pretty sure you couldn't have screwed it up.

[acjx880]

Maybe I'll take the tach from my gf's Outback tomorrow night after she's asleep and try it out in my car to see if there's any difference. =P
So then I'll at least know if it's the tach or something else...