What is Freezing Frame Data, Why You Need It: A How-To Guide

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Obtaining Freeze Frame Data From Your Cars ECU

Obtaining Freeze Frame Data from Your Cars ECU - Image by TPN TV

The OBD2 freeze frame data may look like a meaningless set of symbols, numbers, and acronyms to the untrained eye. But what is this data if not an expert mechanic?

If you don't know what it means, you should find out. The OBD2 freeze frame data will be discussed in the following article and why it may be necessary for anyone who owns or drives a car.

What is Freeze Frame Data?

The "freeze frame" is when your car says that there is a problem and that this might make the Check Engine Light (CEL) go on. The OBDII system saves what it was like before the problem happened. When a problem occurs during the first two consecutive trips, all information from all sensors involved in that engine management function is collected.

As a result, freeze frame data is a picture of what occurred when the issue occurred. Until the code is fixed or until you remove the battery, the data recorded at the time of a problem will stay in this system's fault memory. 

If a defect with a greater priority occurs before the initial code is fixed, such as an issue that threatens to damage the catalytic converter(s) or even the engine, the first freeze frame data may be overridden by the freeze frame data of the more serious codes. 

Freeze frame data comprises some "layers" integrated into a single, coherent message that can be retrieved using standard scan methods. Below are some examples of what makes up a single frame of data.

Freeze Frame Data Indications

The data from OBD2 freeze frames are more than just numbers. The freeze frame shows the PID or parameter ID values when a diagnostic trouble code (DTC) is activated.  Due to the presence of the issue code, the check engine light will illuminate.

Similar Conditions Window

When a problem stops a readiness monitor from running or completing, this layer holds information regarding engine operation when the monitor is functioning. Generally, the engine load in MAP (Manifold Absolute Pressure) data and the engine speed are recorded.

It's worth noting that there are two Similar Conditions Windows, one for the fuel system and the other for misfire detection. If the fuel system fails, the OBD II system records the actual MAP value and engine speed to see if there was a possible connection between the fuel delivery strategy and engine speed/load when the failure occurred. 

If so, the system changes from "YES" to "NO." The stored MAP value refers to the engine load, i.e., the engine idling or at full throttle when the failure happened, whereas the engine speed value informed the user of the engine speed when the failure occurred.

Adaptive Memory Factor

The ECU computes the total fuel adjustments necessary over a given period, rather than a predetermined distance using both long and short-term fuel trim values. This guarantees that fuel consumption does not exceed the restrictions set by the emission control system.

Similar Conditions Time Window

The engine's duration without any faults being present is tracked by this window, which is limited only by all identical conditions being met. A so-called "good trip" counter is kept for each failure-free journey.

Fuel System Good Trip Counter

The Common Engine Light (CEL) will turn off when the ignition is switched OFF after the car has been driven for a few seconds. The CEL light may be turned on by using the key fob or pressing the Start/Stop button, but it cannot be turned off this way. 

How to Read Freeze Frame Data?

It is dependent on the type of OBD2 scanner. Reading freeze frame data with a professional OBD2 scan tool like the Autel AL519 or Bluedriver is a piece of cake. It's self-evident if you understand how a modern engine works.

The meanings of many of the readings are self-explanatory. Engine RPM, airflow rate, fuel rail pressure gauge, vehicle speed sensor, and Engine Coolant Temperature (ECT) are all reasonably simple to comprehend. When the trouble code is detected, the data shown provides a snapshot of what the engine sensors have been doing.

What if you don't have a more sophisticated scan tool? This is when things start to get complicated. Let's look at what typical freeze frame data looks like and then analyze it piece by piece:

  • Fuel SYS1 CL
  • Fuel SYS2 N/A
  • DTC P0261
  • P0261 Cylinder 1 injector circuit low

All of those acronyms, symbols, and numbers are meaningless to the typical vehicle owner. Let's take a look at each code, and see the definition of what it means!

  • DTC P0261 - This is the DTC, or Generic OBD2 Trouble Code, which is a diagnosis code that all automobiles can understand.
  • Fuel SYS1 CL - When bank 1's fuel injector is in closed-loop mode, it receives an error.
  • Fuel SYS2 N/A - A no-fuel injector in bank 2 means that the engine is four or six-cylinder with just one bank.
  • ECT (Engine Coolant Temperature) - This is a measuring temperature unit. The coolant temperature in this situation is 223 degrees Fahrenheit.
  • Load PCT 87 - The motor's air volume is below 100%.
  • SHrtFT1 2.6 - This code means short-term fuel trim is at 2.6%.
  • Long FT1 -3.0 - The fuel injectors have not yet been switched to long-term fuel trim because the oxygen or O2 sensor hasn't changed.
  • Map kpa 26.3 - When the error occurs, the reading from the manifold absolute pressure sensor or MAP. The sensor produces a pressure signal of 26.3 kPa in this example.
  • VSS 48 - This code indicates the vehicle's current speed when the DTC was triggered.
  • Rpm 1495 - This was the number of engine revolutions per minute when the error occurred.
  • IAT 57 - The PCM detected a diagnostic trouble code when the intake air temperature was 57 degrees F.

Now, keep in mind that the data indicated above may vary depending on the vehicle's make and model, OBD2 protocol, and the type of OBD2 scan tool used to retrieve the freeze frame data, but this should be a decent basic explanation to get you started!

How OBD2 System Store Freeze Frame Data?

Understanding the two types of system monitors is necessary to know how an OBD2 system maintains the freeze frame data.

  1. Continuous monitors - This implies that the monitors are continuously on and operational anytime the vehicle is running. The fuel trim and misfire detectors are two continuous monitors. It's known as a "one-trip" emissions diagnostic monitor since it allows the powertrain control module (PCM or vehicle ECU) to save a diagnostic issue code together with the required freeze frame data right away.
  2. Two-trip or non-continuous monitors - Oxygen sensors, heaters, the EGR system, evaporative emissions, and the catalytic converter will be tested once every trip. However, the PCM will keep a diagnostic issue code until the next trip with two-trip monitors. The temporary fault code will be erased from the ECU memory if the failure occurs during the second journey.

Note: The ECU will save a DTC along with the necessary freeze-frame data if the fault happens again on the next trip. Also, keep in mind that the freeze frame data will not be refreshed or updated if the test cycle fails again. The freeze frame data will be altered only if the system detects an engine misfire or fuel trim problems.

How OBD2 System Clear the Freeze Frame Data?

So, let's imagine your vehicle's check engine light is on. The CEL or MIL will be switched off if the malfunction does not occur after three travels. The fault code and freeze frame data, on the other hand, will stay in the ECU memory. This is referred to as automatic clearing.

But what if the OBD2 scanner is plugged in and no freeze frame data is found? This is unlikely to happen if the PCM activates the check engine light, but it can. If your automobile goes through around 40 warm-up cycles without identifying a problem, the PCM will automatically remove the issue code and freeze frame data.

However, more essential data from continuous monitoring, such as engine misfires and fuel trim, may overwrite the freeze frame data. Misfire and fuel supply fault codes will always take precedence over other non-continuous fault codes.

Can I Manually Clear Freeze Frame Data?

To manually remove any related trouble codes and freeze frame data, you need a good scan tool like the BAFX or Bluedriver. The CEL in the instrument console will also be turned off due to this procedure. To wipe or remove the data, follow the instructions on the OBD2 scanner. Here are some pointers on how to pick a good scanner:

If the problem is not resolved, the check engine light, together with the error number and associated freeze frame data, will return. This is why you should only erase or delete DTC and freeze frame data once the problem's cause has been identified and/or replaced.

Conclusion

Freeze frame data can help in the diagnosis of many of your vehicle's underlying issues. You'll be able to spot trends in your car's performance, especially those that cause faults or problems, using the OBD II system. 

You'll be well on your way to having your vehicle back in perfect functioning condition with the right scan tools and a little diagnostic trouble code (DTC) research. We hope you now have a thorough understanding of how to view OBD2 freeze frame data.