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I reassembling my engine and have located all connections on my 1999, 3.6 L , 6 speed, carrera , cabrio....except one.

It is located right behind the alternator and is missing a home. Is this an extra diagnostic plug or an outdated connection for an updated alternator design or am I missing something ? it is the plug in the picture with the red pick blade under it.



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Thansk Loren. right on the money. I had connected the wrong plug to to the valve on secondary air. Now I have ethe extra wire below that is on the left back of motor near AOS. lthe plug wires are red with blue stripe and red with purple stripe. Do you know of a link to a wiring diagram for the 1999,3.4, c2, cabrio, 6 speed?



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I am in the same situation (99 996 C2 Tiptronic). I am reassembling and can't find a couple connections. Can you send me a color coded wiring diagram. I took lots of photos prior to removal but still confused.

thanks you

I sent phil53chevy 1 sheet for what he needed.

The wiring diagram for MY1999 is 26 sheets.

You can buy them (individually) at the Porsche PIWIS TSI website or get them all in the Bentley 996 Manual.

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I am attaching a pre-disassembly pic that shows the "mystery wire" laying peacefully on the top of the engine with no partner.

I am at a loss for where it goes. I REALLY want to believe it is an accessory wire or an extra.

follow the black wire sheathing from the front of the AOS untill the female plug appears in front of the starter.

maybe the dealer will know but am hoping my rentechers are more clever.


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Got your PM.

Are you sure it isn't for the knock sensor (it looks like it would connect to the knock sensor right below the plug in your pic).

Are both of your knock sensors connected?

IIRC though both of the knock sensors have different style connectors.

Of course connectors can and do change with different MYs.

That looks more like the kind for a fuel injector, throttle position sensor, change over valve, EVAP valve, etc...

Edited by logray
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Is your EVAP valve connected ? It is a valve that sits between a hose that goes into the throttle body and a fuel hose going to the evap system in the front of the car. The valve normally sits above your alternator near the intake manifold.

Mine has a red wire with blue stripe and a purple wire.

Edited by logray
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both knock sensors connected, evalp valve above alternator connected, all secondary air connected, all injectors, maf, throttle possition, alt, a/c, ....everything lined up perfectly.,yesterday on Rennlist I saw a post with the exact same wire missing a home. i will find and post link and have asked the poster if he ever resolved his issue. his last post was that he put it back together unconnectd and has been driving with no CEL. I think it is a spare as his picture shows a "plug" in the end of the wire but would love to know what it COULD have connectd to...C4 diiferential, autotrans , its a fairly long wire.


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Yes it could very well be a spare wire. There are tons of different versions of the main engine wiring harness. There are lots of possibilities like you point out. Auto, PSM, PSE, etc. In fact there is probably another spare connector in the corner of your engine bay psngr side for emissions, and it is not connected, so your idea is certainly valid.

My car did not have any spares, then again it is an early 99 build. When I had my engine apart I literally took tape, wrote down what it was for, and stuck the tape onto the connector.

I'm sure you've gone over the engine many times, and if you have everything connected, I would just put er back in and fire it up.

Worst case you've got some sorting to do later, but as long as you have the big things connected such as fuel and spark and they are in the correct locations any cel you might have would not be destructive. SAL, EVAP, etc are not going to cause a misfire.

Some of the sensors are also important such as cam and crank sensors, but they have much different connector styles.

Maybe just leave the wire somewhere where you can get to it easily if you need to.

Oh, isn't there a smallish connector similar to that one for the regulator on the back of the alternator? Did you connect that one too? And your throttle position sensor (and IACV if you have one?) are connected, although IIRC IACV is 3 wire, but TPS might be 2 wire.

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yep, alternator connected, cam(s) and crank sensor. I zip tied it to top of intake so I can get to it. follow the link i am attaching to rennlist and this guy has the same deal. My car is early '99 with a factory replace in 2005.

thanks for your help


Edited by Loren
link corrected
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