Disabling "Post" O2 Sensor on OBDII 460 EFi
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Tuned
Joined: Apr 2003
Posts: 351
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From: Davis County, UT
Disabling "Post" O2 Sensor on OBDII 460 EFi
I am trying to figure out how to disable the "post" O2 sensor (sensor after the catalytic convertor). I am not running a CAT and I don't want my check engine light to trip because all the 02 sensors are reading the same reading. I also don't want the computer leaning out the fuel two much because the POST 02 sensor is giving the same reading as the PRE sensors. I am going to be running this in a '71 F-250 - that why am not running a CAT.
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From: Cloud USA
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From: Cullman Alabama
1 watt resistor
A one Watt Resistor might work.
I dont know the value of the O2 sensor in question, but all of the snesors convert what they 'see' to a voltage the Compputer can 'see'.
So get somebody to measure the resistance of the warm O2 sensor and simply plug a 1 watt resistor of that value into the 2 pin connector to the O2 sensor.
Sometimes the trouble shooting information will tell you what resistance to expect. If you know what voltage to expect, use a trip pot to figure out what resistance you need. But you will need a good quality resistor. Ceramic would be good.
I dont know the value of the O2 sensor in question, but all of the snesors convert what they 'see' to a voltage the Compputer can 'see'.
So get somebody to measure the resistance of the warm O2 sensor and simply plug a 1 watt resistor of that value into the 2 pin connector to the O2 sensor.
Sometimes the trouble shooting information will tell you what resistance to expect. If you know what voltage to expect, use a trip pot to figure out what resistance you need. But you will need a good quality resistor. Ceramic would be good.
New User
Joined: Oct 2004
Posts: 16
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From: Montrose, CO
O2 sensor...
I do not see how using a resistor would simulate an O2 sensor.
An O2 sensor generates voltage based on oxygen it "sees".
A voltage is developed across a resistor based on the current flowing through it.
Jim
An O2 sensor generates voltage based on oxygen it "sees".
A voltage is developed across a resistor based on the current flowing through it.
Jim
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From: Cullman Alabama
FordPartsOnly
O2 sensor generates a Voltage?
Do you mean something like the Piezo electric type voltage? Heat the Rock, or Squeeze the Rock?
I thought (and still do think) the O2 sensor is a Variable resistor. More or less Oxygen in the mixture changed the value of the Resistor in the circuit.
Similar to the Cad Cell in the heart of the household Furnace.
So somewhere in the middle of the range, would be what we want the Computer to see.
It's possible the code writers may have wanted the Computer to see the sensor output as 'cold' on startup, and lean out as the engine warms.
So the sensor port might have to vary in order to keep the fault code from showing up.
If you have been to school on this. The School says the O2 Sensor generates a voltage, then you'd be right.
In that case, to dupe the PC into thinking the O2 Sensor was working, you would make a parallel circuit, using the 12 V Battery source, which would present the correct voltage to the sensor port at the Computer.
Does your trouble shooting manual say what we should see at the port?
This is interesting! C'mon back.
O2 sensor generates a Voltage?
Do you mean something like the Piezo electric type voltage? Heat the Rock, or Squeeze the Rock?
I thought (and still do think) the O2 sensor is a Variable resistor. More or less Oxygen in the mixture changed the value of the Resistor in the circuit.
Similar to the Cad Cell in the heart of the household Furnace.
So somewhere in the middle of the range, would be what we want the Computer to see.
It's possible the code writers may have wanted the Computer to see the sensor output as 'cold' on startup, and lean out as the engine warms.
So the sensor port might have to vary in order to keep the fault code from showing up.
If you have been to school on this. The School says the O2 Sensor generates a voltage, then you'd be right.
In that case, to dupe the PC into thinking the O2 Sensor was working, you would make a parallel circuit, using the 12 V Battery source, which would present the correct voltage to the sensor port at the Computer.
Does your trouble shooting manual say what we should see at the port?
This is interesting! C'mon back.
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New User
Joined: Oct 2004
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From: Montrose, CO
O2 sensor...
In response to our discussion about O2 sensors, there is a very good article in IMPORT CAR magazine this month. The web site is www.import-car.com and in the right side of the home page is the title "In This Month's Issue..." and the article is called "Selling Oxygen Sensors".
If someone has problems finding it and wants a copy, I can email it to you.
The typical range of an O2 sensor is 0.1V to 1.0V and this voltage is continuously changing (looking at it on an oscilloscope).
Thanks,
Jim
If someone has problems finding it and wants a copy, I can email it to you.
The typical range of an O2 sensor is 0.1V to 1.0V and this voltage is continuously changing (looking at it on an oscilloscope).
Thanks,
Jim
Last edited by FordPartsOnly; Nov 18, 2004 at 07:45 PM.
New User
Joined: Nov 2004
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O2 Sensor operation
He's right The O2 sensor generates a voltage between about .3v and 1v and sends it to the ECM so that it can do it's thing as far as enriching or leaning the fuel mixture. If the rear sensor reads the same as the front sensor because of the non existant cat it will excessively lean his mixture and he'll also get tired of seeing the check engine light.
Originally Posted by Thudpucker
FordPartsOnly
O2 sensor generates a Voltage?
Do you mean something like the Piezo electric type voltage? Heat the Rock, or Squeeze the Rock?
I thought (and still do think) the O2 sensor is a Variable resistor. More or less Oxygen in the mixture changed the value of the Resistor in the circuit.
Similar to the Cad Cell in the heart of the household Furnace.
So somewhere in the middle of the range, would be what we want the Computer to see.
It's possible the code writers may have wanted the Computer to see the sensor output as 'cold' on startup, and lean out as the engine warms.
So the sensor port might have to vary in order to keep the fault code from showing up.
If you have been to school on this. The School says the O2 Sensor generates a voltage, then you'd be right.
In that case, to dupe the PC into thinking the O2 Sensor was working, you would make a parallel circuit, using the 12 V Battery source, which would present the correct voltage to the sensor port at the Computer.
Does your trouble shooting manual say what we should see at the port?
This is interesting! C'mon back.
O2 sensor generates a Voltage?
Do you mean something like the Piezo electric type voltage? Heat the Rock, or Squeeze the Rock?
I thought (and still do think) the O2 sensor is a Variable resistor. More or less Oxygen in the mixture changed the value of the Resistor in the circuit.
Similar to the Cad Cell in the heart of the household Furnace.
So somewhere in the middle of the range, would be what we want the Computer to see.
It's possible the code writers may have wanted the Computer to see the sensor output as 'cold' on startup, and lean out as the engine warms.
So the sensor port might have to vary in order to keep the fault code from showing up.
If you have been to school on this. The School says the O2 Sensor generates a voltage, then you'd be right.
In that case, to dupe the PC into thinking the O2 Sensor was working, you would make a parallel circuit, using the 12 V Battery source, which would present the correct voltage to the sensor port at the Computer.
Does your trouble shooting manual say what we should see at the port?
This is interesting! C'mon back.
Junior User
Joined: Jan 2001
Posts: 81
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Ford PCMs use the downstream (post cat) O2 to calculate converter effeciency. This is to guage the health of the cat and throw a trouble code when you need to replace the cat. It does not effect the fuel metering. The closed loop fuel metering is done by the upstream O2 sensors.
I am addressing the same issue adding a 1996 OBD-II computer in my 1994 Bronco with a 460.
460 computers that support Mass Air are all reflashable. They all are set up for 3 O2 sensors as well.
Just my two cents,
John
I am addressing the same issue adding a 1996 OBD-II computer in my 1994 Bronco with a 460.
460 computers that support Mass Air are all reflashable. They all are set up for 3 O2 sensors as well.
Just my two cents,
John
New User
Joined: Oct 2004
Posts: 16
Likes: 0
From: Montrose, CO
460 Odbii
John,
I do not have much experience with 96 and newer ECUs. Is there a source for the factory parameters, that a person could tweak from that point?
Thanks,
Jim D6TZ@msn.com
I do not have much experience with 96 and newer ECUs. Is there a source for the factory parameters, that a person could tweak from that point?
Thanks,
Jim D6TZ@msn.com
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