Freeze Frame Diagnostics

Freeze Frame Diagnostics

Freeze frame data is a "snap shot" of when the code occurs of the specific sensor PIDs.

More than 20 years ago, automakers and the EPA developed the standard that we know today as OBDII. This standardized many of the onboard emissions protocols and codes and allowed states to perform onboard emissions testing. For technicians, it opened a whole new world of diagnostics. As time passed, even large trucks and motorcycles adopted this same method to test the emissions status of a vehicle.

As part of OBDII, Mode$02 for the logging of freeze frame data was created. This diagnostic protocol saves data PIDs and information when a code is set. In 1995, freeze frame gave technicians a powerful diagnostic tool that was previously only available on expensive factory tools – and it’s still useful today. 

What is Freeze Frame Data?

Without going into details concerning the types of codes and monitors, freeze frame data is a “snap shot” of when the code occurs of the specific sensor PIDs. In general, the newer the vehicle, the greater number of PIDs in a freeze frame. These PIDs focus on the how the engine burns fuel and manages emissions. You will not find data for the variable valve timing or other devices that might be unique to the manufacturer. 

Chances are you have a scan tool that offers specific make and model coverage and generic/global OBDII. But, in some cases, the fastest way to get to the bottom of a check engine light might be to access the vehicle with generic protocols.

Most engine control modules store only one freeze frame record per code. The freeze frame data is stored when a test fails or a DTC is set. The freeze frame is not updated with current values. If the code P0171 for bank one is too lean, and if the criteria for the code are set again, it will overwrite the previous freeze frame data.

What is contained in freeze frame data?

On some vehicles, the freeze frame data is limited to data PIDs focused on a narrow set of values that determine the fuel system performance and emissions. These can include rpm, fuel system status, calculated engine load, readings of absolute pressure,  readings from the MAP sensor or MAF sensor, spark advance, throttle position, coolant temperature, long- and short-term fuel trims, vehicle speed, voltage,  MIL status, EVAP status  and EGR status.

Depending on the vehicle and code, the amount of information can vary. But there are several key pieces of information you need to look for:

  • What was the vehicle doing at the time the code was set?
  • What was the coolant temperature and fuel system status?
  • Did the problem occur at idle or under load, and at what rpm?
  • What are the fuel trims, and what are the differences between the short- and long-term?

From this information, you can replicate the problem on a test drive faster. Other information can include vital “nuggets” of information like battery voltage, fuel pressure and EVAP status that can point you in the right direction faster than just going on the code alone. 

Limitations of Freeze Frame data

The main limitation of freeze frame is it captures only when the code triggered and not the events that occurred before or after. Also, freeze frame data is limited to standardized codes and there is typically never freeze frame information for body or chassis codes. 

Freeze frame data does not stay around forever. If a scan tool clears a code, or the code is cleared due to prerequisite number of trips or drive cycles, the freeze frame data might be erased.

You May Also Like

Using a Scope

Ignition coil and plug diagnostics.

Scope-diagnostics

A secondary ignition waveform is not just about the coil; it is also about the resistance of the air and fuel mixture inside the combustion chamber. When you are looking at a secondary ignition waveform, you need to be looking at the spikes and the hash in between. Measuring the voltage of the secondary ignition directly is not an option. The high voltages will damage any scope or meter. Capturing a secondary ignition waveform requires a capacitive probe. This type of probe can be either the traditional clamp over an ignition wire or a “paddle” that makes contact with the surface of the coil or wire.

Diagnostic Procedures For Stop/Start Systems

Stop/start technology is more than just a switch wired to the brake pedal and starter.

Auxiliary Cooling Pumps

An auxiliary cooling pump’s primary function is to circulate warm coolant to the heater core.

Battery Management Means Knowing How It Ages

The battery may be fully charged, but you also need to measure how low the voltages go while the engine is cranking.

Detecting Misfire And Knock Conditions

Knock sensors are mounted on the block near the base of the cylinder head.

Other Posts

BMW Spark Plug Replacement

Here are a few things that you need to know before replacing spark plugs in a BMW.

Diagnosing Intercooler Boost Trouble Code P0299

The criteria for setting the code is very basic.

Alternators and Ripple Voltage

The alternator produces an AC current that must be converted into DC current by way of a rectifier.

Hybrid Vehicle Fluid Maintenance

There are opportunities your shop can’t pass up just because the car or SUV has a hybrid badge on the back.