OBD2 Freeze Frame explained

OBD2 Freeze Frame is a simple but powerful tool when trying to diagnose car malfunctions. Freeze Frame provides insight into the conditions that were present when a malfunction occurred. This post will explain in detail what the Freeze Frame is.

What is Freeze Frame?

In simple terms, a freeze frame is a snapshot of data. It’s a snapshot of sensor or component readings (parameter values) captured at the moment when the electronic control unit detected a malfunction. In addition, the freeze frame contains the Diagnostic Trouble Code (DTC) that the computer system identified as the reason for the malfunction.


OBDII Freeze Frame with the Android app
OBDII Freeze Frame with the Android app


Quite often, the car might have multiple DTCs simultaneously when some fault or faults occur. In this case, you cannot tell what DTC was the first one and caused the Malfunction Indicator Light (MIL) to light. The DTC that’s part of the Freeze Frame will reveal to you the DTC that is the main cause for the problems and occurred first.

The sensor data values stored in the frame help you figure out what might be wrong with your vehicle. However, sometimes coming to conclusions might need some guesswork. Experience with engines and cars will help when analyzing the possible solutions to fix the malfunctions.

For example, when an engine misfire is detected, a snapshot of the current sensor values is captured. The engine control unit stores this snapshot data along with the DTC, and it’s called a freeze frame. The causing DTC might be P0301 Cylinder 1 Misfire Detected, for example.

All OBD2 compliant cars are required to support Freeze Frame. It’s an essential part of onboard diagnostics.

How to read the Freeze Frame?

As the Freeze Frame is an integral part of the OBD2, basically all OBD2 scanners can access and present the snapshot data to you. Reading the Freeze Frame data with OBD Auto Doctor is straightforward. The software fetches the data from the car and gives it to you in a human-readable format.

Whether you are using the computer software or the mobile app, navigate to Trouble Codes -> Freeze Frame.


OBDII Freeze Frame with the macOS software
OBDII Freeze Frame with the macOS software


It’s rather essential to read the Freeze Frame data as soon as it’s stored because most cars can provide only a single Freeze Frame. In some cases, a new Freeze Frame snapshot will override the previously stored data, and you will lose the older data. For instance, an engine misfire will most likely override the previous content. In any case, you should notice that the Freeze Frame is not stored indefinitely.

Can there be multiple freeze frames?

Sure, the OBD2 specification allows the manufacturers to save additional freeze frames. The conditions for storing these extra frames and the content of them are manufacturer-specific.

Is it possible that there’s no freeze frame data stored?

Yes, in some real-world examples, we have seen cases when the Check Engine Light (CEL) was turned on, and OBDII Trouble Code was set without providing a Freeze Frame. The frame was either not stored at all or automatically deleted after multiple successful warm-up cycles. It is not a typical case to happen, but it’s possible.

Is it possible that there’s a Freeze Frame without an Engine Malfunction light?

Yes, in some cases, the car might automatically remove the Engine Malfunction light and the related OBD2 codes. Depending on the severity of the issues, this might happen after multiple warm-up cycles without the problem present. However, the car computer should not clear the Freeze Frame data in this case. Looking at the Freeze Frame snapshot gives you a hint of an intermittent problem.

Can I reset the Freeze Frame?

Yes, you can use OBD Auto Doctor to reset and clear the Freeze Frame. Freeze Frame is removed when you reset the MIL and clear the OBD2 trouble codes. It’s an all-in-one action that resets all the diagnostics data in the car. However, the trouble codes and other data will come back if the problem is detected again.





Dark mode now available for iOS and Android

Earlier this year, we were happy to make the announcement of the updated mobile apps in our Twitter account. Dark mode can extend your phone’s battery life significantly. It might be also easier for your eyes in low light conditions. OBD Auto Doctor honors your phone’s system settings to use or not to use the dark theme. You have full control of the used theme.

Both Android and iOS apps got support for the dark mode / theme. On Android, the dark theme can be used in all supported app versions back to Android 5. With iOS, the dark mode is supported only in iOS 13 and newer. This is because the platform restrictions and Apple not backporting new features to old iOS versions.

If you are new to on-board diagnostic, or regular DIYer, now you can run car diagnostics in the dark! Update the app from the store and get ready!

Android: Google Play

iOS: App Store


Dark Mode screenshot on iOS 13 (iPhone 11)
Dark Mode screenshot on iOS 13
Dark Theme screenshot on Android 10 (Pixel 3 XL)
Dark Theme screenshot on Android 10






What an automotive mechanic thinks about Auto Doctor?

This is a guest post by Tim Miller. He’s an automotive mechanic from Colorado. Read on what he thinks about OBD Auto Doctor.

What is OBD Auto Doctor?

Given the name, you can imagine this OBD2 application can diagnose and cure problematic symptoms in your vehicle - all this without scheduling an appointment.

While this doctor is unlike most others, the OBD Auto Doctor is an advanced software that puts the medicine in your hands.

With this software you are able to use your PC, Mac or Mobile device to read and clear diagnostic codes from your car’s onboard diagnostics module. Either computer, tablet or smartphone can be your home mechanic with OBD Auto Doctor.

If you want to get to know your car’s diagnostics better and put all the tools into your handheld device, this is just a simple download.

With this software you will be able to find out why the check engine light or the MIL is blinking. Above all, it will tell you what steps you need to take to turn it off.

Additionally, you will have access to live data streaming and graphing in order to monitor your engine’s performance and make sure your car can pass emissions tests.

If you are tired of overpaying at the dealer, it’s time to upgrade your future repairs with a device that can help you save time and money.

What does it do: Features and Functions?

With the OBD Auto Doctor, you simply have to attach the adapter to your vehicles OBD2 port. OBD Auto Doctor is the best application for most of the trusted Bluetooth OBD2 adapters in the market.

This device will act as your personal communicator between your car’s computer and your mobile device.

Using Bluetooth, WiFi connection, serial port, or USB connection, you can utilize many ways to begin communicating and diagnosis your vehicles internal needs.

You will be able to turn your mobile device into a tool to help read Diagnosis Trouble Codes (DTCs) that appear when a malfunction is detected, such as confirmed codes, pending codes, or permanent codes.

Access to Freeze Frame data in order to capture live data from your engine at the exact time a malfunction is detected.

Beyond just reading the DTCs with a library full of over 18,000 trouble codes, this will also clear the check engine light.

Additionally, you’ll have access to readiness monitors to test the emissions of your vehicle, with the OBD Auto Doctor two readiness groups will be displayed.

Check your emission test yourself with this device, it will tell you the status of your vehicle since the last cleared DTC, as well as the status for the current driving cycle.

It is also loaded with various sensors and modulators that can help you monitor your vehicle in real time.

Some sensors include coolant temperatures, fuel pressure, manifold absolute pressure and airflow pressure.

One nice feature is the availability of both the metric and imperial system, making this device universally adaptable.

Moreso, you can perform oxygen sensor monitor tests, onboard diagnostics monitoring, and find ECU information.

Tell me the Pros and Cons

All is good here:

  • Compatible with Windows, Mac, and Linux - Turn your computer into your comprehensive auto scanner with this next level technology.

  • Transferable data - Unlike some software which only allows you to use with one computer, the license key for OBD2 Auto Doctor can be transferred from each computer you own.

  • Multilingual functionality - With a user-friendly setup, you will have access to twelve different languages.

  • DTC database with 18000 trouble codes - You no longer have to look up an unknown trouble code, with an extensive database, the definition is at your fingertips.

  • Accurate diagnosis - With freeze frame data, clear emission readiness tests as well as sensor and parameter graphs, you will gain extensive knowledge about your vehicle, from the inside out.

What you need to know:

  • Subscription setup - In order to keep the OBD2 Auto Doctor updated and accurate, you’ll have to pay for updates along the way. To this end, the subscription model is quite flexible depending on your needs. Namely, if you want to use the software on a computer, it’s a single purchase.

Will it work with your device and vehicle: Compatibility?

The software works on Windows, Linux and Mac computers. For mobile devices, OBD Auto Doctor supports all iOS, Android and Windows phone. However, if you’re using iPhone or iPad you just need to check if it is a Bluetooth Low Energy adapter.

As long as you have an OBD2 compliant vehicle, OBD Auto Doctor should work for you.

This means you should double check if an OBD2 port is readily available within your vehicle, this is normal protocol for all vehicles newer than 1996 in the US or 2001/2004 in Europe.

However, if your car is an older model, this technology may not be suitable to assist you with vehicle diagnosis.

Who is it built for?

This technology is useful for those people in or outside of the automotive world.

If you’re a car enthusiast who would like to monitor your vehicle’s systems and stop paying dealership fees, the OBD Auto Doctor can help you have all the tools you need while keeping money in your pocket.

If you’re more involved in the automotive industry, such as a modern DIY mechanic, or small repair shop owner, OBD Auto Doctor technology can help reduce the time you spend trying to figure out a complication within a vehicle.

With OBD Auto Doctor monitoring all OBD2 systems and diagnosis, you will be able to identify and repair small problems before they become a big hassle.


Tim Miller profile photo

I’m Tim Miller, an automotive mechanic and blogger from Denver, Colorado. I’m the founder of obdstation.com, the automotive blog about OBD2 scan tools. My fanpage is facebook.com/autozikcom or twitter.com/autozik. I’ve had over 10 years experience in car repair and using OBD scanners. Some of my review articles about car diagnostic tools can be found on my own website obdstation.com.





How does lambda affect fuel consumption?

The engine fuel rate parameter ($5E) is supported only by rather new OBD2 compliant cars. The engine gives real-time data on how it’s consuming fuel with this parameter. But don’t worry even if your car doesn’t support it.

OBD Auto Doctor provides the calculated fuel consumption for almost every car. The software calculates the estimated fuel consumption based on several other parameters. The formula is a bit different depending on what parameters your car supports and what fuel it uses.

What is lambda?

In car diagnostics domain, air-fuel equivalence ratio is often regarded as lambda (λ). This is especially true in spoken language. Air-fuel equivalence ratio is the ratio of actual air-fuel ratio (AFR) to stoichiometry for a given mixture. In other words, lambda is the ratio between the amount of oxygen actually present in a combustion chamber versus the amount that should have been present to get perfect combustion.

  • In an ideal mixture, there’s exactly the amount of oxygen required to burn the amount of fuel present. Thus, lambda = 1.0.

  • In a lean mixture, there’s too much oxygen for the amount of fuel. Thus, lambda > 1.0.

  • In a rich mixture, there’s too little oxygen for the amount of fuel. Thus, lambda will be < 1.0.

In practice, the AFR devices measure the amount of residual oxygen or unburnt hydrocarbons in the exhaust gas. The engine monitors the lambda values in a feedback loop to adjust the air-fuel mixture.

OBD Auto Doctor uses the lambda values for the fuel consumption calculations. This is to get the most accurate estimation of fuel consumed.

Sources, and more information available at Air-fuel ratio on Wikipedia and Lambda as a Diagnostic Tool.

Lambda in practice

We did an experiment to find out how the lambda values affect the calculated fuel consumption in practice. In a data set A, we fetched the real lambda values from the car, and used those in the calculations. In a data set B, we assumed that the mixture was ideal all the time. In this case, the value of 1.0 was used as the lambda value.

We drove a sample track and measured both data sets during the same drive. Below is a graph containing the results. Click the image for larger view.


Fuel consumption with ideal and measured lambda
Fuel consumption chart from the csv data. Click for large image.


As you can see from the image, the ideal vs measured lambda doesn’t have too much impact in fuel consumption calculations. When driving at a constant speed, the difference is barely noticeable. During and after acceleration and deceleration, you can observe the change easier.

With this experiment, the average consumption with the ideal lambda was 5.69 [l/100km] while with the measured lambda it was 5.64 [l/100km]. So on average, the calculations are accurate even without the measured lambda value. However, with other engines and car models, the change can be different. This data was collected from 2.0 liter TFSI gasoline engine.





Torque, engine power and boost pressure added

A few days ago we launched the updated OBD Auto Doctor software. This time our main focus was in calculated performance parameters such as Engine Torque, Engine Horsepower and Turbo Boost Pressure.

You can now measure the performance of your car by monitoring these new sensors in real time. Read further to get insight into the details.


Torque, Engine Power and Boost Pressure
Engine performance sensors chart from the csv data, saved using Google Sheets


Engine Power or Horsepower

Engine power (or horsepower) can be estimated quite well using vehicle speed and its change over very short period of time. The total weight of the vehicle is also needed for valid results.

OBD Auto Doctor measures the engine power at the wheels. This is not the same as at the flywheel. Therefore, if the vehicle speed doesn’t change, the power will show zero. The horsepower will be greater than zero only when the vehicle is accelerating.

The software will also take power loss due to drag into consideration when calculating the power. An average drag coefficient and vehicle frontal area are used.

You can set the vehicle weight in the app settings. To get the most accurate weight, drive your car to a weightbridge. You could also estimate the total weight by using manufacturer defined weight added with the passenger weight, fuel weight plus any extra weight included in the vehile.

Torque

Torque is calculated from the engine power and RPM. With these two pieces of information, the torque can be estimated quite accurately. Torque is measured at the wheels just like the engine power.

Since torque is using engine power for the calculation, the vehicle weight is a factor in the calculation. Remember to set the correct weight!

Boost Pressure

Boost pressure value yields from the intake manifold absolute pressure. Barometric pressure is also taken into consideration. Now, the vehicle is required to support MAP (manifold absolute pressure) in order for the boost pressure to appear as supported. Barometric pressure is optional. The default pressure value at sea level is used unless the car provides support for the actual barometric pressure.

Negative pressure values represent vacuum. Positive values are boosted by a turbocharger or supercharger.

Other improvements

Among the new calculated performance parameters, we also added more.

The software has now support for all Mode $06 scaling IDs. The latest OBD2 standard version added 12 new identifiers. OBD Auto Doctor implements now all the new IDs in addition to the old ones.

If you are using the desktop software, download the latest version from the download page. The updated mobile apps can be found from the approriate app stores using your phone.