O2 circuit clarification

[lakedrifter]

With the Key on I should be getting .5v from ECM correct? 02 Sensor plugged in or unplugged?

thanks in advance.

Heath

[lakedrifter]

When I turn the key on, O2 connected I get .18 volts. If I unplug the O2 it drops to 0 volts. I back probed the ECM and have the same result.

[lionelhutz]

The O2 voltage usually seems to be approximately 0.5V until it warms up.

What does the logging software show for voltage? That number should match your measurements when it's working right.

[lakedrifter]

Thanks for the response Lionel. I'm not using tuner software. I just wanted to understand the circuit. I always thought a .5v reference signal was produced by the ECM. It appears that my understanding is incorrect.

The other day I was getting codes 13, 42, 43. I fixed 42 and 43. I found a broken wire at the Spark Control module.

The code 13, still appears after I have been driving for 2 minutes. It never comes on at idle.

I think tonight I will put my meter back on and see what the O2 sensor does with the engine running. I'f I understand it correctly, the voltage will go up as oxygen in the exhaust depletes.

I'm just trying to trouble shoot to find the culprit.

Heath

[lakedrifter]

Ok so all the codes are back, 13, 42, 43. Any suggestions on where to start looking. A buddy suggested the ECM grounds so Im checking those now.

[lakedrifter]

I was able to Fix code 42 and 43. Color blindness error. lol

I'm still getting the Code 13 for the oxygen sensor. I relocated the Oxygen sensor to the bung directly behind the left exhaust header. The Code will still reappear.

I checked the resistance on the wire last night and found .3 resistance, so i will be changing the wire out tonight to see if that helps.

Even though I have the resistance I can see the O2 sensor signal fluctuate, but it stops at .7 and never goes above.

[lakedrifter]

OK gents, im at my wits end. I still keep getting a Code 13. I have tried to eliminate everything to my ability.

1) no resistance on O2 wire to ECM, even by passed the wiring harness all together
2) replaced the EVM
3) replaced the O2 sensor again.

If I get on the 02 sensor with my meter, after it warms up it reads about .670 volts. Supposedly if you shoot carb cleaner in the TBI it should make the meter go immediately to .900. Mine does not, it stays at .670.
.
Anyone have any idea or advice?

Heath

[lakedrifter]

Ok Im still getting the code 13.

1) Ive made sure there is no resistance on the wire back to the ecm, even by passed the harness all together
2) Put in a new ECM
3) Added extra grounding strap from the head to the exhaust

I continue to get Code 13.

My O2 sensor stays at about 6.7. It does not fluctuate. If I spray carb spray in the TBI, the o2 sensor stays at 6.7 or so. It does not go to .900 as testing procedures say.

Does anyone have any advice at all?

Heath

[lakedrifter]

Finally a solution!!!! Since i finally noticed the ECM had its own ground for the o2 sensor.

High resistance was the issue. Clipped it at the ECM for now and grounded it back to the block.

No more code 13.

Finally... there was peace in the valley once more.