[tedybear]

Hello all.

Finally got around to checking out the scan tool I picked up. And of course I needed to get one that would service all the cars in the family, not just VW. (Sorry RossTech)

As expected we do have some issues that may be playing up with the P0420 code. Namely the fuel trim numbers. The short term trim numbers are right where they should be. Long term? Hosed and out of whack. Below are a few of the data shots:

Live Data
Number of DTCs stored in this ECU 1
Fuel system 1 statusCL
Fuel System 2 status--
Calculated LOAD Value(%)20.4
Engine Coolant Temperature(¡£C)93
Short Term Fuel Trim -Bank 1(%)-2.3
Long Term Fuel Trim - Bank 1(%)9.4
Engine RPM(rpm) 2731
Vehicle Speed Sensor(km/h)90
Ignition Timing Advanece for #1 Cylinder(¡£)27.5
Intake Air Temperature(¡£C)-4
Air Flow Rate from Mass Air Flow(g/s)14.00
Absolute Throttle Position(%)10.2
Commanded Secondary Air StatusOFF
Location of Oxygen SensorsB1S12--B2S----
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.630
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
OBD requirements to which vehicle is designedOBD&OBDII
Equivalence Ratio (lambda)(Bank 1-Sensor 1)1.008
Oxygen Sensor Current(Bank 1-Sensor 1)(mA)0.016

Now I'm not the sharpest knife in the bulb box. (bad pun) But it looks like the engine is running rich for the long term trim. And the other oddball question? I can interpret the O2 sensor bank 2--that should be the one after the converter. (I would hope)

But I'm in the woods as to the bank-1-sensor-1 only showing current and not voltage? Should this not be a voltage reading I'm looking at?

I know this little bug has some issues and it appears to be running a bit on the rich side. Just looking for some information on why the tool would only report amps on the front sensor? Or am I missing something simple?

S-

 

[red99]

With a plus sign on the fuel trim the engine is said to be running lean. The ECU is adding more fuel than should be needed based on the MAF reading, therefore the engine would be lean if not for the correction based on the O2 sensor. Abnormal is considered to be above +15% or below -15%, so you are in the normal range. A lean fuel trim can be caused by a dirty MAF sensor or vacuum leak.

Bank 1 sensor 1 is the front O2 sensor and bank 1 sensor 2 is the rear one. An engine with more than one catalytic converter (such as a V-engine) would have bank 2 sensors. Not sure why one is reading in amps. You may be able to change the reading type on the scan tool somehow. It probably has to do with what data the tool is requesting from the ECU.

 

[tedybear]

Found this posting reply on a general automotive forum. It makes sense--and at the same time I have to wonder about a 2001 car using a "Wide Band" o2 sensor:

The o2 sensor that has current flow readings is a wide range o2 sensor. instead of the old fashioned o2 sensor that uses a signal voltage between 0-1 volt to tell the computer how rich/lean the engine is running, wide range o2 sensors use current(amps in the sensor circuit, not exhaust current). A rich condition will cause a negative current, and lean condition will cause a positive current, and at stoichiometry (air fuel ratio at 14.7:1) there is no current. the amount of current in either direction dictates how rich/lean the engine is running. in your case, the reading on your scan tool is telling you the vehicle is running lean. the fuel trim and lambda readings agree.

I did not find any settings in the scan tool for changing what the o2's read out. I think for the sake of comparing the results I'll swing by the local Advance Auto store and have them hook up their scan tool and see what the o2's are doing and reporting back to the engine computer. The scan tool I purchased has a fairly recent flash memory upgrade (listed as Aug of 2013...sat on the shelf a bit LOL, but it's still pretty recent)

This is quite interesting.

S-