PCM Snapshot Data

PCM SNAPSHOT ON CODE SET (FREEZE FRAME, FAILURE RECORDS)
When a PCM DTC sets, the PCM does several things. Among them is to save useful data and input parameter information for service diagnosis. This information is referred to as Freeze Frame, Failure Records. You will see references to these in many PCM DTC trouble charts because this information can be useful in pinpointing a problem even if the problem is not present when the vehicle is in the service bay.

Freeze Frame, Failure Records save relevant data parameters with a DTC snapshot. Which data parameters are saved varies based on the DTC set. Transaxle DTC snapshots generally contain transaxle related data parameters while fuel DTC snapshots generally contain fuel related data parameters. If several DTC(s) are set, snapshots for the three most recently set DTC(s) will be saved.

Freeze Frame, Failure Records data may be retrieved through the DTC menu on scan tool. When Fail Rec. is selected, snapshots on DTC set will appear first in the order the DTC(s) were set, most recent first.

Keep in mind that once Freeze Frame or Failure Record is selected, the parameter and input data displayed will look just like the normal PCM data except the parameters will not vary since it is displaying recorded data.

PCM SNAPSHOT USING A SCAN TOOL
PCM snapshot data may also be taken and retrieved using a diagnostic tool by selecting the SNAPSHOT option. These parameters may then be viewed right away. This snapshot will only be saved while the diagnostic tool is in use.

Keep in mind that once Snapshot is triggered, the parameter and input data displayed will look just like the normal PCM parameter and input data with the same parameter numbers except it will not vary since it is displaying recorded data.

DIAGNOSING INTERMITTENTS USING PCM SNAPSHOTS
PCM snapshots may be very useful in diagnosing powertrain problems. Data stored by the scan tool, or when a PCM DTC was set may be retrieved and used to determine if a particular input was incorrect when the problem occurred. Many of the PCM DTC trouble charts will use Freeze Frame Failure Records information to pinpoint a problem if it is not current. For example, the trouble chart for DTC P1810 uses the gear ratio snapshot data parameter to indicate what gear the transaxle was in when the DTC set. This information may be used along with the transaxle pressure switch indication to zero in on the circuit(s) that are intermittently shorted or open. Snapshot on DTC set data may even be used, as in DTC P1350 trouble chart, to determine whether the engine was running or not. This is an important piece of data in diagnosing DTC P1350. In order to use PCM snapshot data that was recorded by the scan tool, you must first understand what problem the driver was experiencing, Once this is understood, any appropriate parameters may be retrieved and any abnormal parameter readings used to pinpoint what sensor or system is causing the problem. For example, say a vehicle comes in with an intermittent rough engine condition and a snapshot was taken while the engine was running rough. Several data parameters may be retrieved and an abnormal parameter noted. MAP sensor, ECT sensor, IAT sensor, and knock sensor parameters may be compared to normal values of those parameters and any values that are out of the normal range investigated. Also, fuel injector pulse width or spark advance may be retrieved. This may indicate a fueling or ignition irregularity that should be investigated. While this method may result in increased diagnosis time, it also results in less actual repair time and fewer service comebacks.