Socal_Tom

While the harness goes out to be rebuild there are some test results that indicate problems to be addressed.

1) I don't have ground at pin 23 which is the O2 sensor ground shield. Is that like a bad O2 sensor itself?



2) When I jumper the AFC relay from pin 30 to both pin 87's I only have 11 volts at pin 85. My understanding is that pin 85 is + hot line to activate the relay coil, so not having 12v here would render the relay inoperative but not stop the car from running if there is a three-way jumper from 30 to 87 & 87, right?

Landseer

I don't have it either, but I have replaced the sensor properly.

Am also scratching my head on the lack of ground signal at that pin.

Socal_Tom

Huh, well I suppose that is one less thing to worry about!

Anyone else with the same system also have a healthy car without that pin being grounded?

rjtw

I can't answer your question, but now I'm curious... as I recall, the O2 sensor has just a single wire (on my '83 Ljet)... thus why would there be both a signal pin AND a ground shield pin? Any idea where that pin leads?

Also, off topic, but any idea what pin 11 does and what it's connected to? I'm wondering if it has anything to do with the crazy little upshift light on the dash that in my car stopped working when the car was still almost new! Don't miss it but curious!

Rick

Socal_Tom

Bump for good questions!

And for some 16v love.

Ducman82

pin 11 if not the MPG gauge if your car has it.

if i remember right, the O2 sensor shield wire is grounded IN the computer on the L-jet, so unplugged you would get nothing.

if the relay is that finicky over 1 volt. your relays sucks.

Socal_Tom

Hi guys - did some more research and am wondering about the value on pin 85 as noted above.

I believe pin 85 is a control, along with 86, for the relay. I believe 85 is the ground side of it, so why would it have 12v with 30 and both 87s jumped but nothing else plugged in? In fact, wouldn't any power on 86 without a jumper from 86 to it indicate an issue?

86 senses a current, passes that along to 85. That trips 30 sending power to both 87s. Right?

Socal_Tom

OK - this has been bugging me so I spent some more time on it. Turns out, if I am reading the wiring diagram correctly, that Porsche is NOT using the DIN standard here and they reversed the current flow compared to the DIN standard. So 85 is control hot and 86 control ground.

Cripes!

To Ducman's point that suggests that if you have 11+ here you are probably OK.