Electrical ground for exhaust system

[bp71k5]

Just by accident yesterday, I am finding that my exhaust system is not grounded. The manifolds have a solid ground, but after the donut gaskets on the manifold, there is no continuity to ground, including where my o2 sensor is screwed in.
Doesn't the o2 sensor require the pipe to be grounded? I haven't seen anything in winaldl that tells me the o2 sensor isn't working.


-Brian

 

[K85 Octane]

I have an A/F gauge in my dash, it doesn't work unless I'm grounded to one of the header bolts. My wire is tied around one of the AC bracket-to manifold bolts.

 

[4X4HIGH]

I know that a 2 wire sensor (heated 02 sensor, one wire is the signal wire and the other receives 12 volts) does require the exhaust system to be grounded but a 3 wire sensor (heated 02 sensor, one wire is the signal wire, one wire receives 12 volts and the last one is a ground) doesn't require the exhaust to be grounded since the 3rd wire of the sensor is a ground wire for the heating element.

 

[bp71k5]

I know that a 2 wire sensor (heated 02 sensor, one wire is the signal wire and the other receives 12 volts) does require the exhaust system to be grounded but a 3 wire sensor (heated 02 sensor, one wire is the signal wire, one wire receives 12 volts and the last one is a ground) doesn't require the exhaust to be grounded since the 3rd wire of the sensor is a ground wire for the heating element.

When i installed the three wire sensor, the two heater wires are the same color so i just hooked up one of them to 12v and grounded the other. Is the heater element grounded to the sensor housing?

-Brian

 

[British Slave]

Just by accident yesterday, I am finding that my exhaust system is not grounded. The manifolds have a solid ground, but after the donut gaskets on the manifold, there is no continuity to ground, including where my o2 sensor is screwed in.
Doesn't the o2 sensor require the pipe to be grounded? I haven't seen anything in winaldl that tells me the o2 sensor isn't working.


-Brian

Isn't it grounded thru the bolts in the donut clamp?

 

[bp71k5]

Isn't it grounded thru the bolts in the donut clamp?

I assumed it was, but I get no continuity on it from my meter.


-Brian

 

[4X4HIGH]

I assumed it was, but I get no continuity on it from my meter.


-Brian

So you've hooked your DVOM from the chassis to the exhaust pipe and no continuity? If that's the case I think I would check your meter out to make sure it doesn't have a problem. There are 6 bolts holding the exhaust pipe to the manifolds and I find it hard to believe that none of them are grounding the exhaust pipe.

 

[bp71k5]

There are 6 bolts holding the exhaust pipe to the manifolds and I find it hard to believe that none of them are grounding the exhaust pipe.

I find it hard to believe too. The meter works fine between two points on the pipe, between the frame and the body, and everywhere else Ivan think of. Actually, the o2 sensor heater is even grounded to the body so I'm super confused. I'll have two twist some of the mounting nuts and see if there's just corrosion causing the problem.




-Brian

 

[496truck]

Don't bother. The exhaust does not need to have any kind of electrical connection to the rest of the system.

An O2 sensor creates it's own voltage via a chemical reaction, only after it reaches a certain temp. Which is why car makers started going to heated O2 sensors over the older 1 wire sensors. The heaters bring them up to operating temp faster thus putting the system into open/closed loop (I can't remember which is which) faster. The older 1 wire sensors simply created their voltage signal once they reached temp. No other electrical signal is required.

I may be fuzzy on every detail but that's the basics that I can remember from 5 years (total) of auto repair school/training. And quickly aproaching 20 years ago now.

 

[K85 Octane]

496:
I don't know squat. There, that's out of the way.
I'm not cool enough for this newer stuff, so my A/F gauge is connected to a 1 wire O2 in the header.
Posi - fuse panel
Sender - wire on O2
Ground - wire to header bolt

nothing works without all of three connected and the best ground (engine ground required by autometer) was at the header bolt.

having said all that, I doubt any of that helped lol, prolly way over my head anyway