Diagnosing Intermittents Using Snapshot

INTERMITTENT PROBLEMS
Powertrain Control Module (PCM) snapshots may be very useful in diagnosing intermittent powertrain problems. Data stored while in on-board diagnostics, or when a PCM code was set may be retrieved and used to determine if a particular input was incorrect when the problem occurred. Many of the PCM diagnostic trouble code trees will use Snapshot on code set information to pinpoint a problem if it is not current.

UNDERSTANDING THE CUSTOMER'S PROBLEM
In order to use PCM snapshot data that was recorded in on-board diagnostics, you must first understand what problem the driver was trying to capture in the snapshot. 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. Manifold Absolute Pressure (MAP) sensor, Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor parameters may be compared to normal values of those parameters and any values that are out of the normal range investigated. While this method may result in increased diagnosis time, it also results in less actual repair time and fewer service comebacks.