Before On-Board Diagnostics

Before any diagnostic testing is done on a vehicle some preliminary checks must be performed, as outlined. Be sure to write down the findings, especially any DTC, for future reference.
1. Know and understand the customer concern.
2. Verify customer concern (when does it exist?)
- Upshift.
- Downshift.
- Coasting.
- Engagement.
- Noise/vibration.
If noise/vibration, check for dependencies:
- rpm
- Vehicle speed
- Shift
- Gear
- Range
- Temperature
3. Vehicle at normal operating temperature.
4. Check transmission fluid level and condition.
5. Visually inspect the vehicle for the following items:
- Vehicle modifications
- Electronic add-on items
- Leaks
- Proper linkage adjustments
6. Check TSBs for concern information.
7. Perform the complete On-Board Diagnostic procedures (KOEO, KOER).