my down pipe is only like 12" long and i placed the o2 bung about 3-4" away from the open end. my single wire 02 wont get hot enough to function since the pipe is so short ( open DP ) so i am gonna use a 4 wire with a heater in it.. i was just gonna wire the signal wire to the ecu and the heater i was gonna wire in with the cars accessory wire. will this work? to my understanding the pinout is :

grn= to ground
black= 12V+ (to acc wire)
other blk = heater ( should this be a + or a ground? )
wht= goes to ecu signal

 

the heater is only designed to be powered for a limited time (during warm up) so the heater element it may not last long.

black - ACC
black - ground

 

someone else said both black are + ????

 

the O2 heater is a 12V device, it requires 12V across the terminals to make it active.
one side has to be ground, the other 12V.

normally the ECU supplies the ground signal to turn it on. (other side is to 12V ignition)
With the car running after a few minutes if you check the O2 heater line from the ECU, it will read 12V. Because the ECU turns off the heater after the car has been running for a little while.
This is the common mistake when reading O2 heater operation. The other mistake is some ECUs only power the heater is the car is running, so just switching on the ignition you will see 12V on both lines as well.

in your case you have switched 12V, so the other has to be ground.

one other thought that just crossed my head, I wouldn't use the ACC line to power it. Typically that's low load items, unless your car is gutted and you run next to nothing in it, I'd run the heater to the 12V ignition Run position. more power on reserve and will only be on when the car is on.

 

ok i got it wired up. and ya i wired it to the main 12v run wire.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">With the car running after a few minutes if you check the O2 heater line from the ECU, it will read 12V. Because the ECU turns off the heater after the car has been running for a little while.</TD></TR></TABLE>
That depends alot, O2 sensors actually stop heating when they reach operational temp and start heating again if the temp falls below the set degrees. If your O2 sensor is very far down the pipe, it will need heat almost all the time when you're not gunning it, because it will cool down fast and lose the signal.
I wired mine directly to a 12V source and its working just fine. it might not last forever, but what does, nothing in this life.