AEM O2 sensor oxygen sensor installation, routing
 

Ladies and Gents: I bought an AEM O2 sensor and gauge system install in my 1973.5 911 with 3.2 CIS engine. I could use some advice with routing the wires. If some of you have some good tricks for how to do it, or can refer me to another thread where this has already been beat to death, please share.

I welded the bungs into both SSI exhaust headers, and today I spent a couple hours poking and prodding and figuring out the best way to route the wires from the sensor to the gauge. The gauge will be on or under the dash somewhere, but I haven't decided that yet. I'll probably stick it somewhere convenient and start using it before making a final decision where to mount permanently.

Getting the wires from the engine compartment into the car seems more difficult than it should be. I tried to poke a coat hanger through the penetrations where the wire harness and battery cable now enter the tunnel near the front of the transmission. I had great difficulty pushing a stiff wire (coat hanger) through these channels, and the hard lines were in the way of getting a straight shot and view. I finally stopped and figured I should ask the brain trust here, since surely some of you have done this already!

So what's the trick? Or should I be routing it into the car some other way?

I used the access created by the speedometer cable into the center tunnel. Once the wire is in the tunnel, bring it out under the back seat access panel on the floor, then route it under the carpet to the front, and under the dash. I actually have several wires routed through the same port, and used another grommet to seal it off under the car. Works great.

This is exactly how I did mine too.

Wire through the speedometer wire rubber, through the tunnel, up the wiring access point to the left of the driver's footwell.

Thanks for the suggestions of going through the speedo cable location. Yes, I have a speedo cable, not wires. I was able to easily fish a coat hanger through there, but was somewhat reluctant to leave the boot loose between the car and the cable connection on the tranny. Oh well, it probably doesn't matter, and it's easier than trying to fish it through the existing wire harness location. Maybe the next time I drop the engine and have more room to work I'll find a more elegant solution.

Follow up: I installed the sensor in the exhaust after the collector on the driver side, then routed the harness through the speedo cable boot, as recommended, and through the tunnel to the footwell area, then up to the dash. Under the dash, I found a circuit that's live when the ignition is ON. I used the black/green/white wire coming from the hazard light switch, which conveniently has an in-line OE spade connector right under the hard switch, so I didn't have to cut into anything. I just made a short Y with connectors on each leg so I could plug it in between the OE connectors and have a tap for the power to the gauge.

Then I plugged everything in, and the gauge didn't work. When first plugged in, the LEDs on the face of the gauge flashed intermittently and randomly, maybe every 10 seconds. As I have been troubleshooting, they flash even less frequently. I unplugged and replugged the gauge many times. I tapped the gauge and wiggled the connectors but those actions do not seem to make any difference. I tried with and without the sensor connected I checked for 12v on the red pin of the connector and ground on the black pin of the connector at least a half dozen times. The fine pins in the gauge were not bent. The wiring to the gauge appears to be correct and powered. I do not have a data logger or other external devices attached.

I called AEM tech support and the guy said to fill out the email info he would send me, then destroy the gauge, send them a picture of it, and they would send me a new gauge only (leave the sensor and harnesses where I installed them). That was today, so I hope a new gauge will ship out on Monday and I'll get it next week.

Yep you got a bad one , I'm glad they are sending a new one .
They have trouble with QC

Ian

I junked my AEM when it threw a "code 9" and tech support said "we have no idea what's wrong"
I am using an Autometer now with a analog needle gauge and like it better, just remember you need the long wire kit.