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Discussion Starter #1
Hi all,
I just ran a live test data on my mk1 with Forscan and noticed that the O2 sensor bank 2 shows 0 volt (O2 bank 1 around 0.79 V), and the throttle position TP was at 16%.
Does it indicate that the second O2 sensor is not functioning and needs to be replaced?
Also the TP seems high as I expected it should be around 5%, any advice on how to reduce it?

thanks in advance
 

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You have NO bank 2 sensor, that is for V6 and V8. Why you get errant readings. The TPS is about right at that number, mine read 19%. Can't 'reduce it' anyway, locked into the clocking of the part and that cannot be changed.
 

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^^^ Yup

A normal scan tool would show N/A for sensors not used (at least my cheap one does). Any "bank 2" reports for your engine are spurious.

That TP "percentage" isn't an actual throttle opening percentage as amc mentioned, it's a reference value the ECU uses for it's calculations (percent of ref. voltage returned?) as it determines the throttle position for fuel/spark calculations.
 

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My Focus has 2- O2 sensors. One pre-cat, and one post cat. That should be common to all OBD2 engines. I don't know about overseas vehicles, but what I've been reading lately is that there is not much difference on pollution and therefore engine controls in OBD2 vehicles.

It is possible that your bank 2 O2 sensor is bad, but those can read 0 in perfect conditions. Typically those sensors last about 100-150k miles, so if your vehicle has more mileage than that then the sensor is suspect. I probably need to replace both of mine, but I'm just lazy- LOL
 

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Bank One, Sensor #1 - #2 - #3 if used should be the way it reads
 

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X2, common callout is bank 1 sensor 1, bank 1 sensor 2 (after cat) on a four cylinder but some have extras (sensor 3 most likely). When engine becomes a multiple bank or two rows of cylinders (6 or 8) then you use the 'bank 2' term. A four has no bank 2 since a single row engine, now a FLAT or opposed or vee four? Another subject.
 

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Discussion Starter #7
thanks for the replies, is there any way to get the exact value of throttle opening position by a software?
So you mean in a 4 cylinder engine like mine there is only 1 O2 sensor? I had a look at some online stores and they are selling two different types of O2 sensors, one before the CAT, and one after the CAT.
 

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Nope, there are 2. Bank 1 sensor 1 = pre-cat, Bank 1 sensor 2 = post cat.

Do you have a CEL at all? If there was something wrong with the O2 sensor (other than age) it would show up as a check engine light.

Bank 2 responses have more to do with the programming of your Forscan. It just wants to give you something even though nothing is there.
 

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Discussion Starter #9
I don't get any check engine error light at all. I am going to replace the catalytic converter as it is dead for a while and I wanted to make sure whether I should order it or not, I thought in the period that CAT wasn't functioning, it might have damage the sensor and that was my concern why it didn't show any value for the second sensor (post cat).

What do you mean by CEL?
 

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Software is never going to know the exact throttle opening without inputting some actual (estimates) yourself. For example, it can "see" a normal throttle closed % value from the TP sensor, but it doesn't know what % that is from an actual fully closed value you never hit because of the throttle crack built in (throttle stop screw).

ECU has a pretty good idea of where it is, but it's main concern is how it changes & the relationship to air flow estimated by other means (the MAF in this case) as well as RPM etc. to calculate fuel input & spark timing. Fuel & timing need to be changed based on all the inputs, throttle opening is just one of them.

You could get rough numbers for yourself if you recorded TP% at idle opening, half throttle & full throttle for curiosities sake.
 

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Yesterday I was answering post #7 while you typed post #9.

CEL = Check Engine Light, and you mentioned you don't have one.

What makes you think the CAT hasn't been working for a while? Details would help out with responses.

"defective" CAT wouldn't hurt an O2 sensor.


The question on the "bank 2" sensor is answered at this point, you don't have one so any "readings" for one mean nothing. You have bank one sensor one & bank one sensor two.

Inexpensive Dongles & Apps don't give a lot of explanation, just a lot of data you need to interpret in most cases. This one is giving you a "zero" reading for an item, rather than telling you N/A (Not Applicable) for your engine.

Early computer folks invented a term for this - GIGO for "Garbage In, Garbage Out". Without an input to that system telling it to ignore (or report N/A) any items not used in the car, it instead reports a "zero" value. If the user doesn't know in advance that the item doesn't exist on that vehicle, it looks like something has been tested and is either defective or actually reporting a "zero" value.
 

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Forget the cat if you are not getting codes on it.

Forget absolute TPS idle numbers as well, each one changed may vary a bit, the PCM simply uses the start % and then extrapolates the range after it gets a chance to view the swing amount. Meaning absolute TPS idle % is worthless to you. You are FINE like you are.
 
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