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Here’s How To Become a Car Whisperer Using OBD2 Live Data

how to use live data to diagnose car problems

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Using the live data function of the FIXD scanner and app allows you to literally talk to your car when diagnosing most check engine light problems.



What is Live Data?



Today’s automobiles are filled with advanced technologies controlled by various computer systems, and each computer operates through numerous sensors. A problem in any system is quickly relayed to the driver through a check engine light, and the use of an OBD2 scan tool helps show what area of the vehicle is experiencing a fault. All of these sensors and computers are able to display live data in real time to provide easier diagnostics, but you need to have the right scan tool in order to do so. That’s where the FIXD scanner and app comes into play offering the ability to not only read and clear any diagnostic trouble codes but also show live data to make repairing modern vehicles much more possible for DIY mechanics.



Benefits of Live Engine Sensor Data



Simply knowing the diagnostic trouble code that caused a malfunction indicator light to come on isn’t always enough to repair the condition. A check engine light can be triggered by a number of different components from a faulty sensor to bad wiring, so before you go junkyarding to throw a new part on your car, you should slow down and attempt to properly diagnose the root cause. On top of that, some powertrain and driveability issues won’t always result in a check engine light. That’s where OBD2 live data readouts come in handy.



The real advantage of viewing live sensor data is seeing how the engine and its computerized systems are behaving in real time. Information from this data can then help DIY mechanics narrow down the origin of a certain problem by revealing what parts may be faulty or confirm the proper operation and continue diagnosis. This includes anything from air and fuel mixture, emissions, engine speed, and more. 



A good example of when viewing live OBD2 data would be most helpful is in the case of a check engine light that comes on intermittently. Even for a seasoned mechanic, this can be extremely frustrating, but having the ability to view live OBD2 data through the FIXD scanner can make the job a little easier. 



In this scenario, the check engine light could be cleared, and then the live data would show exactly what conditions are present for the light to come back on as indicated by the amount of run time, distance traveled, and the number of warm-ups that have occurred since the code was cleared. 



Also, if the diagnostic trouble code indicates a faulty sensor, double checking the live data could verify the part is actually bad (and not another condition such as bad wiring) before spending the money on a new sensor.



How to View Your Car’s Live Data with FIXD





The first thing you need to do when using live data to diagnose a problem with your car is to plug the FIXD scanner into your car’s OBD2 port and fire up the app on your smartphone. To use the scanner and app, the engine needs to be running. 



Although it depends on what type of issue you are trying to diagnose, most diagnostic tests require that the engine is operating in a closed loop, which means that the engine is warmed up. This refers to the engine’s computers and sensors being in a closed loop, and you can usually hear when this happens after you start your engine and the idle drops to a quieter rpm once it gets warmer.



Once your engine is warmed up, click on the “Toolbox” tab in the FIXD app to see live vehicle data.



View Live Data and Track Down Your Problem





All gasoline-powered cars, trucks, SUVs and vans built after 1996 have an OBD2 port (diesel trucks, 2008 and newer), but the parameters that are available in the FIXD scanner live data display will vary by the year, make and model of your vehicle. In the vehicle I used for this article (a Kia Telluride), the sensor was able to read almost four dozen parameters from the Engine Control Module, which were then shown in real time (up to four at a time) on my smartphone.



Below Is the List of Live Data Feeds Allowed Through the FIXD App As Read From A Kia Telluride SUV



Calculated Engine Load



Engine Coolant Temperature



Engine RPM



Vehicle Speed



Throttle Position



Run Time Since Engine Start



Distance Traveled with MIL On



Warm-Ups Since Codes Cleared



Distance Traveled Since Codes Cleared



Control Module Voltage



Short Term Fuel Trim Bank 1



Long Term Fuel Trim Bank 1



Short Term Fuel Trim Bank 2



Long Term Fuel Trim Bank 2



Intake Manifold Absolute Pressure



Timing Advance



Intake Air Temperature



Oxygen Sensor 2 Voltage



Oxygen Sensor 6 Voltage



Command Evaporative Purge



Fuel Tank Level Input



Evap System Vapor Pressure



Absolute Barometric Pressure



Oxygen Sensor 1 Current



Oxygen Sensor 5 Current



Catalyst Temperature: Bank 1 Sensor 1



Catalyst Temperature: Bank 2 Sensor 1



Catalyst Temperature: Bank 1 Sensor 2



Catalyst Temperature: Bank 2 Sensor 2



Absolute Load Value



Fuel-Air Commanded Equivalence Ratio



Relative Throttle Position



Ambient Air Temperature



Absolute Throttle Position B



Absolute Throttle Position D



Absolute Throttle Position E



Command Throttle Actuator



Time Run With MIL On



Time Since Trouble Codes Cleared



Short Term Secondary Oxygen Sensor Trim Bank 1



Long Term Secondary Oxygen Sensor Trim Bank 1



Short Term Secondary Oxygen Sensor Trim Bank 2



Long Term Secondary Oxygen Sensor Trim Bank 2



Fuel Rail Absolute Pressure



Actual Engine-Percent Torque



Engine Reference Torque



How to Read and Interpret Live Sensor Data



As you can see with the Kia example, FIXD shows a wide range of live sensor data. But for you, this list might look much different. Regardless of what data you can view on your make and model, here’s a high-level breakdown of what to look for with the most common OBD2 live data readings:



Fuel Trims: Short Term Fuel Trim (STFT) and Long Term Fuel Trim



Fuel trims are important when it comes to understanding how the ECU (engine control unit)  or ECM (engine control module) is controlling fuel delivery to the engine. The role of the ECM is to ensure your vehicle operates at optimal performance by managing the air-fuel mixture, regulating the emission control systems, and more.



A positive reading of 0.0% or above means more fuel is being added to the air-fuel mixture to compensate for a lean condition, while a negative reading (<0.0%) indicates that the ECU is taking away fuel from the mixture to compensate for a rich condition.



Fuel trims are often displayed as Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). The Long Term Fuel Trim is made up of accumulated data from Short Term Fuel Trim readings and stored as historical data for the ECM to quickly pull from. Short Term Fuel Trim normally runs between -10.0% and 10.0%, and Long Term Fuel Trim levels typically run between -5.0% and 5.0%. When viewing STFT, you should see your data reading shifting rapidly between rich and lean. The LTFT reading will appear more stable.



If you see readings outside of these, it could be an indication that there is another problem with the engine or fuel delivery system. Another common issue that could cause you to see very high fuel trim levels is a vacuum leak. If you see too high or too low readings, investigate further.



Oxygen Sensor Voltage



The oxygen sensor tells you the air-fuel ratio of your exhaust so the engine can make adjustments if more or less fuel is needed to run the car efficiently. FIXD will read this level in terms of voltage. If there’s a perfect ratio of oxygen to fuel, you should get a reading of 0.45V. But since this is virtually never the case, the voltage will probably fluctuate around 0.5V.



Engine Revolutions Per Minute (RPM)



RPM, or revolutions per minute, refers to how fast the engine turns. Knowing your RPM is helpful to decide when to shift gears in a manual transmission, increase mileage by shifting at the right time, determine if your engine and transmission are working properly, and drive your car safely without damaging the engine.



Check your car’s RPM while idling. It should hover between 600-1000 rpm. For trucks, it may be closer to 600 rpm. For motorcycles, it will be higher, around 1000-1500 rpm.



If you see RPM surging, dropping, or stumbling when the engine is warm, this could be a sign of a performance issue that requires attention.



Intake Air Temperature



The intake air temperature (IAT) sensor monitors the temperature of the air entering your vehicle’s engine. The ECM needs this information to balance air-fuel mixture since colder air is denser than hot air and requires more fuel to maintain the same air-fuel ratio.



Normal readings should display a temperature similar to that of the garage or surrounding environment. Otherwise, there may be an issue with the sensor itself, which will trigger an OBD2 trouble code you can read with FIXD.



Engine Coolant Temperature



The ideal operating temperature for an engine is between 190°F and 220°F. If you see readings below this, the ECU will add more fuel to the mixture and raise the idling speed to compensate for cooler temperatures.



Ignition Timing



Setting the correct ignition timing is crucial in a spark ignition internal combustion engine. If a spark happens too early or too late, it can cause vibrations and damage. Ignition timing also affects engine longevity, power, and fuel consumption.



Ignition timing live data can tell you how much time the engine’s computer is adding or subtracting based on sensor inputs.



Mass Air Flow



The mass air flow (MAF) sensor measures the amount of air that enters the intake system of the internal combustion engine. There are multiple types of Mass Air Flow sensors but the most popular are hot wire sensors. An internal air temperature (IAT) sensor is typically installed within the MAF sensor. This air flow sensor helps optimize the air-fuel ratio as well as determine the shift points in the transmission and reduce the amount of exhaust emission.



MAF sensor readings will vary depending on the type of sensor. However, output is often displayed as grams/second or as voltage. Check your owner’s manual for the manufacturer’s specifications for air flow at idle and various engine speeds.



If your engine has a bad MAF sensor, it may be hard to start, hesitate while under load, run rough, or run excessively rich or lean. Sometimes these sensors become contaminated and interfere with their ability to properly read air mass.



If you suspect there’s an issue with your mass air flow sensor, use FIXD to scan for check engine codes. Trouble codes associated with a faulty mass air flow sensor can include:





Manifold Absolute Pressure



Your engine requires the right combination of air, fuel, and spark to run. The manifold absolute pressure (MAP) sensor helps ensure this combo goes off without a hitch so you can get where you’re going trouble-free.



More specifically, the MAP sensor measures the amount of air entering the manifold, the air temperature, and the number of revolutions in the engine. Using this data, your ECU can adjust fuel and airflow to ensure maximum operating efficiency. If your engine isn’t fuel injected, you probably don’t have this sensor.



To interpret MAP sensor data, you’ll need to know how the information is read by the OBD2 scanner. It displays MAP values as pressures measured in inches of Mercury (in. Hg). 1 bar of pressure equals 29.4 in. Hg.



Normal MAP readings are 29.6 in. Hg at sea level with the engine off and around 9.6 in. Hg. while the engine is idling.



Congratulations Car Whisperer



Now that you know what live data is and how to read it with the FIXD scanner and app, you’re on your way to becoming a true car whisperer. Diagnose problems like never before and save hundreds of dollars in repair shop diagnostic fees! If you don’t have an easy-to-use OBD2 scanner like FIXD to read your car’s live data, be sure to check out FIXD today!




Jeffrey N. Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

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About the Author

Jeffrey N. Ross

Jeffrey N. Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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