I have a question about installing my heated o2 sensor. it needs to be tied into the ignition power and ground wires. so i was looking at my super coil and it has negative and positive terminals. i tried reading the wires with the ingition off, and got negative voltage readings. with the key turned to the on position i got a reading of .6 to .7 volts. this seemed really low to me i thought it would be 12 to 14 volts? so anyway i started the car and read the wires still a low voltage is this enough volts to run the 02 sensor. any other sugesstions

 

run it off your fuse block.
Is it a 3 or 4 wire O2 sensor? Are you using this in conjunction with a computer or as a stand alone to tune a non-computer controlled carb?

 

it's a 3 wire sensor. it's gonna be in cojunction with a computer. i'm gonna have my chip reburned. so no super coil right
thanks

 

You should run it off of a main power wire with a relay switched by the fuel pump relay. If you wire it to a keyed power source, the sensor will be heating whenever the key is on (which isn't wrong, just not what I would want personally. If it's triggered by the fuel pump relay, it'll only be on when the car is running (as well as briefly when you first turn the key to on).

Actually, the way I have it wired also uses the air divert solenoid. This way the O² sensor is only heating while the engine is running and the car is in open loop.

I just did it because it's good power management, and I had the wiring harness spread all over the floor in one whole room so it was easy to run the wires.

 

This usually works:

 

vador good diagram, i don't really understand it though, i usally need things things in front of my face to see the big picture what realy is the power wire going to

Jza do you have any pics or drawings of your wiring setup. i'm waiting on my helm shop manual to come in the mail if you know of any referance pages or wiring diagrams to refer my to that would be great

 

79,

I've modified the diagram a bit for clarity. Everything in BLACK already exists on your car. You have to add the relay and wiring that are indicated in RED. One of the wires to the O² sensor is already there (the signal wire). The ground wire needs to be grounded properly, and the heater power wire (pink/black, or whatever color your's is) is routed through the relay as indicated. The EVAP purge solenoid is easily accessible in the engine compartment, which is also a good place to mount the relay. The A.I.R. divert solenoid would work just fine, too, but it tends to cycle more on deceleration conditions. It really doesn't matter a lot, since neither are powered in open loop mode, and thus would assure that the O² heater was ON in that mode.

 

Vader, you got me cornfused.

1. B1 on a 730 ECM is +12V constant hot from the battery. No Ign switch.

2. Your using the normally closed output of the "bosch" type relay, which would remain hot, provided the ECM isn't providing a ground output to A3.

As I read your schematic, the O2 would be hot at all times until the ECM triggers A3. cheers, BW

 

My heated O2 is just key switched. I didnt even think about using the ecm to switch it on...silly me. I'd like to switch mine over this weekend, but I'd just like to clarify something. Is the Dk green with a yellow stripe wire grounded in closed loop and open-circut in open loop? Thanks

 

Vader: It cycles more? How so? I may have to review the book on that and the CCP circuit and revise my circuit if that's so. I've been wanting to anyway because I don't really like taking any juice away from the fuel pump even if it's as piddely as a relay.

 

Could someone answer my question? Many thanks!

 

vader,
i wasn't going to post again for fear of sounding stupid but i'm still confused.
i'm assuming that i can go to radio shack and get a relay but i don't know what kind.
the way i read your diagram is that one side of the relay has keyed power going into it. so the o2 sensor will be heating untill the evap grounds the relay and shuts off the heat?
the ground from the o2 sensor can go to any ground.
the signal goes to where it normally goes
but in your post it says that the evap soleniod is not powered in open loop mode, so how can it power the o2 sensor?
what excatully is a relay doing?
what would the harm be in having the o2 sensor heating at all times the car is on, would it destroy it, or just shortem it's life span?

 

..

 

...

 

SaturnV,

The pinout I'm using was from a '165 ECM, and I was looking at a B+ source instead of the GAGE circuit. The idea was getting an ignition switched source for the relay and sensor heater power. I've gone back and amended my diagrams and FTP'ed them to teh server so they'll always come up the correct way.

ANY relay will work. I used the NC contacts so that the failsafe mode was a closed circuit. The idea is that the relay is de-energized (and O² heaters remain ON) until the ECM is in closed loop. The EVAP does not enable until the ECM achieves closed loop, and disables as soon as it reverts to open loop mode. The theory was that if exhaust heating is adequate to maintain sensor temperature, the heaters do not need to remain energized. You read it exactly right.

Incidentally, the EVAP output is sinking, like most (not "all") other ECM outputs. This was done so that EMI and transianets in the ECM were kept to a bare minimum so that power is a clean as possible and RAM was protected from these transients.

I just happened to pick the EVAP output since the circuit is easly accessible in the engine compartment and is still protected by the GAGE fuse.

- - - - - - - - - - - - - - - - - - - - - - - - - - -
Dan,

Exactly right. The ECM outputs are mostly sinking (provide a ground to complete a circuit - NOT apply power to the circuit). When the EVAP circuit is enabled, A3 will go "low", completing the ground path for the EVAP solenoid, and in this case, the HO2S heater relay. Until then, the O2 heaters will remain ON.

Any 12VDC, continuous duty cycle, SPDT relay will work just fine. Relay current is quite low, but for durability I'd suggest one with at least a 5A rating. The factory replacement relays are well suited to this task, or any P&B or Omron meeting that spec will work fine. Radio Shack relays might be more convenient to acquire, but that's about the only good thing about them.

 

are there any benefits to the heated O2 sensors other than heating up quicker? are they more accurate or do they last longer?

 

i'm kinda confused. i have a 730 ecm, so should i splice into the orange constant hot or a switched pink/black? this is the last thing i need to know to get this damn thing in, so anyone that could say i'd appreciate it.

chevyismine

 

repost

 

Vadors diagram is for the 165. Here is the proper pinout for people running the 730.

165 ...... 730
----------------
B1 ........ BB1
A3 ........ GF7
D3 ........ BD6
D7 ........ GE14