Live Data readings on a scan tool?

I just got a scan tool that reads live data. I’m looking to read live data on a 04 NIssan Sentra which has a P1273 code on it (and a pending P0113 which I don’t think it’s related to each other?). I’m looking to see what the readings are suppose to be around on the scan tool. There 20 readings, I’d like to get what the numbers are on these readings. Or where I can find it because I searched and haven’t yet found it online. I am really looking for the numbers on the MAF and 02B1S1 because it could help figure out the p1273 code and please let me know if there are other reading types I should watch out for. I need to know if the # are in standard or metric?

02B1S1 *

With only 20 data inputs you’re going to be severely limited in what you can figure out. And more important is how fast the data refreshes. If you’re only getting new data every second you’re missing out on more than you’re seeing.

MAF is what the Mass Air Flow sensor is telling the engine computer. It’s a measurement of how much air is going into the engine. Are you reading in volts or grams per second or hertz?

Oxygen sensor bank 1 sensor 1 is the input from that specific sensor. Basically it tells the engine computer whether the engine is running rich or lean. I would expect that sensor to rapidly switch between about 300mv and 700mv at 2500rpm.

asemaster the maf is reading in grams. I tried the scan tool in 2 other newer cars the 02B1S1 was reading 2.000 to 3.500 (V) while driving and stopped when the car was sit hot. That’s why I’m asking, I saw in a couple videos that it should be between .200 - .800

Those codes may be related, and you should always start with the lowest code. P0113 code is a problem with the intake air temp sensor, which works in conjunction with the MAF. With the intake air temp sensor malfunctioning, the MAF cannot accurately measure airflow, which throws off the mixture ratio, possibly causing the P1273 code.

Fix the P0113 code first and it may clear the other code.


“I tried the scan tool in 2 other newer cars the 02B1S1 was reading 2.000 to 3.500 (V) while driving and stopped when the car was sit hot. That’s why I’m asking, I saw in a couple videos that it should be between .200 - .800”

Based on those readings, I’d say the “2 other newer cars” are NOT using oxygen sensors. They seem to be using air/fuel ratio sensors. An entirely different beast

That said, an UPSTREAM oxygen sensor should be fluctuating from below 200mv to above 800mv. The average should be around 450mv

Depending on what vehicle you have, the intake air temperature sensor may actually be part of the MAF sensor. This is a common . . . but not universal . . . practice

The “live data” scan tools can really help out with a difficult problem. The local Chevy dealer connected one to my HHR because it was getting several conflicting fault codes right after a recall “fix.” The scan tool finally got the problem isolated to the Throttle Position Sensor and the Accelerator Position Sensor. Since both are expensive…I did some troubleshooting and found that the crimps on the TPS connector wires were bad from the factory. I simply replaced the connector (with soldered connections) and the problem went away.

I am curious re any newer cars that don’t have O2 sensors @db4690.

My car is 10 years old and has upstream a/f ratio sensors

It has downstream O2 sensors, but their only purpose is to monitor the cat

a/f ratio sensors are more accurate

The Toyota Corolla/Matrix (without the optional engine) went to drive-by-wire throttle and a/f sensors in 2005.

AS db4690 says above, there’s more than one technology used in O2 sensors. The most common type is usually used upstream (directly after the exhaust manifold, before the cat) and that type will measure between 0 to 1 volt usually, it oscillates in this range. Usually more like 0.2 to 0.8 volts. Other types of O2 sensors are used though, and those could well have different voltage outputs. You need to figure out what kind your car has, and which – if it has several – the scanner is measuring. If the O2 reading was out of whack the computer would turn on the check engine light and flag a sensor code or a mixture code I expect.

One of the most useful parameters you scanner measures is the “fuel trim”. those are the parameters with “FT” in them. Suggest you study up a bit on how to use those parameters, as fuel trim can narrow down an engine problem pretty fast, to help you determine if it is caused by air, fuel, or spark.

a/f ratio sensor readings do not fluctuate, like an oxygen sensor reading does

They are NOT referred to as oxygen sensors

One of the reasons . . .

There were some vehicles, where the federal version had oxygen sensors, but the california version had a/f ratio sensors

There have been cases of guys mistakenly replacing a/f ratio sensors with oxygen sensors. They didn’t even plug in without modification. But the boneheads were convinced the new sensor electrical connector had a manufacturing defect. So they modified it to fit . . .


I got live data readings on notepad as a dtc trigger (at idle). I found out sensor 1 is an air fuel ratio sensor not an 02 sensor. The Oxygen Sensor Output Voltage Bank 1-Sensor 1 is reading study but is it suppose to be that low at .265? I tried live data on a 2011 nissan versa and noticed it read 2.500 or so. The main question is can I still get low voltage reading on live data for the air fuel ratio sensor and have it because of an intake leak, fuel pressure, air meter, etc? Or a low voltage reading on the air fuel ratio sensor is because the sensor is bad?

Let me know if there are any other readings out of wack but I would really like to get to the bottom of this p1273 code, with a pending p0113. Noticed the Absolute Throttle Position stood open at idle, on another car i tried it was reading 0.0 at idle.
I put the live data dtc trigger reading notepad on zippyshare, thought it would be to long for a post. But here’s the first part of it.

Live Data
Numbers of DTCs 1
Fuel system 1 statusOL-Fault
Fuel System 2 status–
Calculated Load Value(%)23.5
Engine Coolant Temperature(¡£F)174
Short Term Fuel Trim -Bank 1(%)-1.6
Long Term Fuel Trim - Bank 1(%)7.8
Engine RPM(rpm) 862
Vehicle Speed Sensor(mph)0
Ignition Timing Advanece for #1 Cylinder(¡£)11.0
Intake Air Temperature(¡£F)80
Air Flow Rate from Mass Air Flow Sensor(lb/s)0.01
Absolute Throttle Position(%)1.2
Location of Oxygen SensorsB1S12–B2S----
Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.265
Short Term Fuel Trim Bank 1-Sensor 1(%)-1.6
Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.080
Short Term Fuel Trim Bank 1-Sensor 2(%)N/A
OBD requirements to which vehicle is designedOBDII
Distance Travelled While MIL is Activated(miles)19

Check the intake air temp sensor with an ohmmeter to address P0113.
Has the IAT value been varying test to test, or has it been fixed at 80?
Long term fuel trim at 7.8% is a strong clue.

Agree, the long term fuel trim I shows some kind of problem.

circuitsmith: I only did one test with the scan tool and and the IAT stood at 80-82 that i saw.
The fuel trim being at 7.8, what does that tell you? Is it something fuel related?

And my main question was the air fuel ratio sensor, should that have been steady around .265(V) at idle, or at 2.000-3.000? Would a problem like intake leak, fuel delivery, or just when the sensor is bad would lower the voltage? Looking to rule out the sensor, if that is the problem.

I can’t speak to the sensor voltage issue as I’ve no experience with air/fuel mixture sensors. The typical O2 sensors vary between 0.1 and 0.8 volts usually, but no sure what voltages to expect to see in a/f sensors.

The long term fuel trim expresses the difference in the amount of gasoline the computer thinks would need to be injected for that operating condition, vs what it actually needs to inject to maintain the correct level of O2 in the exhaust stream. When the engine warms up the computer decides how much gasoline to inject by reading the amount of O2 in the exhaust. Ideally there’d be none, as the gasoline would burn it up. But it has no way to determine if there’s too much gas and running rich, so it tries to keep the O2 levels low, but not zero. That’s all in a computer controlled feedback loop.

The long term fuel trim is just an average of the short term. Usually the long term value is less than the short term, as it averages out spikes, and it usually doesn’t vary beyond the +/- 3% range for properly running engines. So a 7.8% is a definite tell-tell sign of something amiss.

What the 7.8% long term fuel trim is saying is that the computer is having to inject 7.8% more gas than that operating condition should require, based upon factors such as the rpm, the intake air flow, the intake air temperature, the throttle position, the intake manifold vacuum, and the engine coolant temperature.

Possible causes, not necessarily in order of likelihood, are:

  • Clogged fuel injectors. The computer is firing the injectors, but not as much gas is getting sprayed out as it thinks.

  • Unmetered air & O2 getting into the engine from vacuum leaks.

  • Inaccurate intake air flow or MAP sensor.

  • Inaccurate engine coolant temp sensor.

  • Faulty throttle position sensor

  • Inaccurate rpm reading

The other possible cause of the fuel trim being off is what I suggested earlier: you also have a fault code for the intake air temp sensor. If the air temp sensor is faulty, the MAF reading will be incorrect, which will result in a fuel/air ratio imbalance, which the computer then tries to correct by changing the fuel trim.

The two codes you have are related. You must address the P0113 code first.