Preliminary Testing

Before any diagnostic testing is done on vehicle, some preliminary checks must be performed, as listed below. Be sure to write down findings, especially any DTCs found, for future reference.
- Check the transmission fluid level and condition.
- Check for add-on items (phones, computers, CB radio, etc.).
- Visually inspect the wiring harness and connectors.
- Check for vehicle modifications.
- Check the shift linkage for proper adjustment.
- Verify the customer concern: upshift, downshift, coasting, engagement, noise/vibration
- The vehicle must be at normal operating temperature.
- Perform vehicle On-Board Diagnostics.
- Record all DTCs.
- Repair all non-transmission codes.