O2 sensor voltage

[NO 5 OH]

Okay... I bought a "modified" version of Autometer's Phantom air/fuel guage for my car several months ago. The "modified" guage is reconfigured only to work at WOT as the range on the guage is only calibrated to operate in the voltage of WOT. You can find the guages as well as other stuff at www.gadgetseller.com When I finally got the car running we had all the guages hooked up, and the boost and fuel pressure guages work fine... but the air/fuel guage has yet to work.

My friend and I check all the connections to see if that was the case... we have 12.6 volts to ground, 12.6 volts to power but only 10.6 volts from the O2 signal wire. We wired the guage up like this: power to 12 volt source, ground to orange ground wire to turbo, O2 signal wire to wire on the pigtail plug in to actual O2 sensor wire. Voltages were checked with key on, engine off. I replaced the O2 sensor less than a year ago with a new Ford Bosch unit, when I completely tuned up the car... so I'm pretty sure the sensor isn't bad. Does anybody have any idea if the O2 voltage is supposed to be that low of voltage or is there something wrong with my testing method?

Please advise

[SVOeric]

if you are getting 10 V from the pigtail that connects to the o2 sensor --

a -- 84-85 you are on the wrong wire !! (3 wire connection)

or

b --85.5-86 You got something SERIOUSLY wrong-- (1 wire connection)


the 02 circuit itself should have a max of 1V ---

I hope you haven't "popped" that gauge -- I'm not sure how it is designed -- but running 10V through something that is designed for 1V is usually a bad thing.

[NO 5 OH]

Originally posted by SVOeric
if you are getting 10 V from the pigtail that connects to the o2 sensor --

a -- 84-85 you are on the wrong wire !! (3 wire connection)

or

b --85.5-86 You got something SERIOUSLY wrong-- (1 wire connection)


the 02 circuit itself should have a max of 1V ---

I hope you haven't "popped" that gauge -- I'm not sure how it is designed -- but running 10V through something that is designed for 1V is usually a bad thing.

Hmmm... interesting point Eric. I've got the wire run to the pigtail that connects to the O2 sensor, shouldn't you see 12 volts power there or am I missing something? I haven't done anything else to it besides hooking up the guage... how could I get a 10 volt reading on something that should only have a max of 1 volt? We took readings of the voltages at different places along the wire thinking it was a bad connection... and it's 10 volts at the pigtail and 10 volts at the guage as well.

I hope I haven't popped the guage either... is there a way to tell somehow?

[65289]

If the mfr. says this is the correct way to connect it, then my point is probably irrelevant, BUT...

I would wonder if the supposed 1v signal level is actually supposed to be 1v coming off the sensor, or if it's actually supposed to be 10v and then dropped down a calibrated amount to 1v by something else in the circuit (resistor wire, etc.). If that's the case, and your new gauge is drawing signal from the sensor itself, that would explain the relatively high voltage. And if that's the case, you'd need to wire into the "dropped down" part of the circuit in order to get the correct signal to your new gauge.

Just fishing for an explanation for your gauge's misbehavior...

[SVOeric]

i did a bit of reasearch ... and here is what I found...
If you measure this voltage with a high impedance digital voltmeter, you will get readings :

1.1 volts (rich)
0.45 volts (ratio 14.7)
0.2 volts (lean)



if you want to get real techie about it... if you have one of the digital A/f meters, here are exactly when the lights come on

VOLTS
RED 1.04
RED 0.96
YEL 0.85
YEL 0.75
GRN 0.62
GRN 0.53
YEL 0.42
YEL 0.32
RED 0.21
RED 0.11


so -- on the 1 wire O2 sensor, if you are putting the black lead to ground, and the other lead on the O2 sensor, and getting 10V -- I'd say you have a wiring issue somewhere!!!!

Maybe a 84-85 type of wiring harnes was swapped in at some point, and someone tapped off the wrong wire ?

[SVOeric]

just to clarify ---

you are running a 1 wire o2 sensor ---

with your volt meter, you put the black probe in a ground location (such as engine block, or base of the 02 sensor) and the other wire to the pigtail where it plugs in ...

right ?

[Pat_in_L.A.]

O2 Sensor

Just a silly old fart with a simple question.

Was this a complete kit that you're installing, or did you maybe get a "deal" on a kit that needs it's own dedicated oxygen sensor? Maybe this gauge needs to run off of it's own signal source. I've seen before where folks have tapped into other sensors and the "sharing" of the signal diluted the intended result. (A good example would be coolant temp sensors. There are three on the car. One for the EFI, one for the gauge, and one to signal the fan controller. None of them share the same function.)

[NO 5 OH]

Originally posted by SVOeric
just to clarify ---

you are running a 1 wire o2 sensor ---

with your volt meter, you put the black probe in a ground location (such as engine block, or base of the 02 sensor) and the other wire to the pigtail where it plugs in ...

right ?

That's the way we did it Eric. We put the ground to the - battery terminal, and the positive on the wire off the 02 pigtail. If this helps out any the car had not been run in probably 10 to 12 hours beforehand. I know the sensor has to have time to heat up... but would that make any difference as to what the voltage should be?

The guage itself is an ordinary Autometer air/fuel guage, but it has been "modified" to narrow the range at what voltage it reads at. The regular air/fuel guage reads from .1 volt all the way to 1.00 volts, whereas the guage I bought reads only from .77 v to .97 v. The range of the guage is narrowed to only read 02 sensor voltage in the upper band, or at wide open throttle. It's not necessary (at least I think) for the guage to register at idle or part throttle cruising cause you really aren't risking damage to your engine from running lean.

I hope this is a better explanation... maybe it'll help shed some light as to what's wrong.



Shannon