O2 Sensor wire shorted - no start

[Johnr352]

So I replaced my O2 sensor and the one thing I read was to make sure the heater wire and ground (?) that connect to the two white wires don’t short out against the metal bracket. Well, that’s exactly what they did. Badly. Car was running fine and then died on the road after about 3 miles. The wires had shorted badly enough that two wires to the car had all but disintegrated into the gray harness sheath. Car turns over but won’t start. Ideas on how to replace those wires?, I suppose, all the way up. And what else is fried? Thanks

[Johnr352]

Any advice and ideas are very very appreciated.

[Snwmble]

Not sure if this will help but Kroon offers different harnesses and o2 plug repair sections. I had an o2 sensor plug disintegrate, and installed their plug section fix. Porsche didn’t sell the harness separately

https://www.kroonwireharnesses.com/porsche-911/porsche-911-1983

[Snwmble]

This is what i replaced in mine but im not sure it’s the same plug as the one that shorted on yours.

https://www.kroonwireharnesses.com/o2-sensor-replacement-connector-with-high-quality-screened-cable-artno-o2conncable

[Johnr352]

Thanks! Yes. Been looking at Kroon but but sure where the other ends connect. Meaning the wires themselves are completely stripped and need to be replaced. To where do those two connect? And then, what would cause crank no start. Did I kill the DME, a relay?

[GH85Carrera]

Did it by chance damage the head temperature sensor wire?

That would cause a no start.

[Johnr352]

I can’t really tell. How could I test that?

[Johnr352]

So, a little research indicates: The other two wires are for the O2 sensor heater, these are white wires. One goes to ground, one goes to the fusebox where its connected to the DME relay. Which one goes to the fusebox doesnt matter, the O2 sensor heater has no polarity. This is for a 944 and would like some help to verify if this is correct. I’m presuming that both the ground and DME relay need to be replaced. Any thoughts on how to run a new wire through the engine compartment to the DME relay? Any easy way to tell if my relay is dead? I presume a dead relay would cause a no start?

[wazzz]

Yes, the DME relay must have fried. It is not fused. You can either replace it (should always have a spare in your glove box) or temporarily short pins 30, 87 and 87b on the connector. This will force power to DME unit and fuel pump and will allow you to start the engine or check that it can be started.
As for the O2 wires, can't help you, my car doesn't have it.

[Johnr352]

Thanks very much. DME relay is easy enough but, as I investigate I have more to do. Both the ground and the heater wire melted their respective harness. I can easily see, after cutting away the sheathing, the melted wire melted the insulation off another ground wire. In the heater wire harness (which includes wires to the coil and engine bay fuse block) the sheathing is burned away and I imagine melted some of those wires too. Harder to see.

Unless otherwise advised, I presume the next step is to pull/remove the engine harness or at least these two sections separately if possible. Repair/replace and reinstall. Anyone know how this is done? Where does the engine harness(es) connect? Can it be done without removing the motor?

[pmax]

Originally Posted by Johnr352

Any advice and ideas are very very appreciated.

[Johnr352]

Originally Posted by pmax

Thanks but this is the least of my issues, as it all started with my fresh install of an O2 sensor. See, when installing, I must have allowed the heater wire to touch the ground or the bracket, causing it all to short out.

[Johnr352]

Originally Posted by Snwmble

Not sure if this will help but Kroon offers different harnesses and o2 plug repair sections. I had an o2 sensor plug disintegrate, and installed their plug section fix. Porsche didn’t sell the harness separately

https://www.kroonwireharnesses.com/porsche-911/porsche-911-1983

Thanks for this. I see now that they have a bunch of different options. I wish the engine harness was made such that it was in sections. Seems like it's one big section that runs up to the relay and DME.

Looking to find some sort of tutorial on all of the various sensor/ connector locations and how to remove the harness without pulling the motor.

[pmax]

This is the engine harness with the bracket attached to the engine tin in front.



Removing it is an engine drop , at least a partial one I presume.

[timmy2]

None of the engine harness attached to the engine, coming from the 14 pin connector goes to the DME. ( Nothing in that engine harness photo.)
Completely separate harness that runs from the rear fuse panel to the DME (Motronic unit) through the firewall.

[timmy2]

I don’t do anything with the Motronic harness. Kroon does for around $1500.

[Johnr352]

Thanks very much. I think I need to fix or likely replace what you show in the picture. If I am observing correctly, the pile of red wires are the grounds that bolt to the left rear side of the motor. The long black sheathed wires are the two heater wires for the O2 sensor (The wires I killed). The other wire attached is for the insulator connection to the O2 sensor? Is that correct? Looking closer, maybe not. I need to fix/ replace the harness that includes the O2 sensor heater wires and sensor wire and from what I now see in a wiring diagram one heater wire goes to the DME relay, the shielded wire goes to the DME itslef and the other heater wire goes to ground. It's just hard for me to tell how their bundled together in the harness itself.

[pmax]

Originally Posted by Johnr352

Thanks very much. I think I need to fix or likely replace what you show in the picture. If I am observing correctly, the pile of red wires are the grounds that bolt to the left rear side of the motor. The long black sheathed wires are the two heater wires for the O2 sensor (The wires I killed). The other wire attached is for the insulator connection to the O2 sensor? Is that correct? Looking closer, maybe not. I need to fix/ replace the harness that includes the O2 sensor heater wires and sensor wire and from what I now see in a wiring diagram one heater wire goes to the DME relay, the shielded wire goes to the DME itslef and the other heater wire goes to ground. It's just hard for me to tell how their bundled together in the harness itself.

The one in the pic 911 607 016 02 is the engine harness but it isn't the DME harness 911 612 173 09.

Hopefully you need just one.

[Johnr352]

Originally Posted by pmax

The one in the pic 911 607 016 02 is the engine harness but it isn't the DME harness 911 612 173 09.

Hopefully you need just one.

Well, I'm not feeling very lucky, but...

I did speak with Pete K at Restoration Design in Canada and he had some advice on the DME harness (173 09). The trick is getting the harness out of the car. From what I can see, after removing 12 or so sensor connections, it routes around the back of the motor, from left to right and then passes through the tunnel. I have not found many good pictures or tutorials on how to get the harness free (with or without the motor in place).