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.
Diagnostic Test Drive
When servicing vehicles with the vehicle stability enhancement system (VSES), test drives will be necessary to allow all tests to be run, and all system functions to be enabled and exercised. A test drive may also be required to duplicate specific DTCs. The diagnostic system check (including test drive) should be run when vehicle repairs are complete in order to verify the repair. The diagnostic test drive will vary for ABS, TCS, or VSES concerns.
The following is a suggested VSES diagnostic test drive:
- Turn OFF the ignition.
- Reconnect any previously disconnected components.
- Start the engine.
- Install a scan tool.
- With the scan tool, observe the VSES Is Centered parameter in the VSES data list. The scan tool will indicate Yes with the steering wheel centered. Drive the vehicle in a straight line for 45 seconds at 24 km/h (15 mph) while monitoring the scan tool.
Remove the scan tool.
NOTEDo not perform any unlawful or unsafe maneuvers.
Drive the vehicle under the following conditions for at least 10 minutes.
- Highway driving.
- Rough roads.
- Perform turning maneuvers (curved freeway entrance ramp, parking lot maneuvers) and high steering angles and yaw rates at low speeds.
- Verify the customers concern and duplicate driving conditions.
- With the engine still running, use the scan tool in order to check for DTCs. If any DTCs are set, repair the concern as necessary.
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 3 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.