For 1990-2009 cars

### History Data

Enhanced diagnostic information is found in the History Data function of the scan tool. Enhanced diagnostic information provides the service technician with specific malfunction occurrence information.

The scan tool will display the last three DTCs to occur, one at a time. The DTC with the most recent occurrence will be displayed first. Each DTC will include the following:

• | The number of drive cycles since the DTC last occurred.

• | The number of occurrences for the DTC since the scan tool DTC information was last cleared.

The most recent DTC will also display various data parameters with values from the time of the DTC occurrence.

### Strategy Based Diagnostics

In difficult diagnostic situations use the above information to identify malfunction occurrence trends. Ask question such as the following:

• | Did the malfunction only occur once over a large number of drive cycles, indicating an unusual condition present when it occurred?

• | Does the malfunction occur infrequently over a large number of drive cycles, indicating that special diagnostic techniques may be required to identify the source of the malfunction?

A malfunction that occurs more frequently increases the odds of finding the cause of the malfunction.

Use the information in order to determine if a DTC is intermittent. Use the information in order to determine if the DTC has not set for long periods of time due to weather changes or a repair prior to this visit.