How To Perform Trouble Diagnosis
BASIC CONCEPT^ To perform trouble diagnosis, it is the most important to have understanding about vehicle systems (control and mechanism) thoroughly.
^ It is also important to clarify customer complaints before inspection.
First of all, reproduce symptoms, and understand them fully.
Ask customer about his/her complaints carefully. In some cases, it will be necessary to check symptoms by driving vehicle with customer.
CAUTION: Customers are not professional. It is dangerous to make an easy guess like "maybe the customer means that...," or "maybe the customer mentions this symptom".
^ It is essential to check symptoms right from the beginning in order to repair malfunctions completely.
For intermittent malfunctions, reproduce symptoms based on interview with customer and past examples. Do not perform inspection on ad hoc basis. Most intermittent malfunctions are caused by poor contacts. In this case, it will be effective to shake suspected harness or connector by hand. When repairing without any symptom diagnosis, you cannot judge if malfunctions have actually been eliminated.
^ After completing diagnosis, always erase diagnostic memory.
^ For intermittent malfunctions, move harness or harness connector by hand. Then check for poor contact or reproduced open circuit.
INTRODUCTION
^ Before troubleshooting, verify customer complaints.
^ If a vehicle malfunction is difficult to reproduce, harnesses, harness connectors or terminals may be malfunctioning. Hold and shake these parts to make sure they are securely connected.
^ When using a circuit tester to measure voltage or resistance of each circuit, be careful not to damage or deform connector terminals.
