1. Verify the problem.
Operate the complete system and list all symptoms as follows:
• Check the accuracy and completeness of the complaint.
• Learn more that might give a clue to the nature and location of the problem.
• Analyze what parts of the system are working.
2. See Section 7 in this manual or the correct chassis manual.
Read the electrical operation for the problem circuit and review the circuit diagram. Understanding electrical operation and the circuit diagram can narrow the cause of the problem to one component or certain parts of the circuit.
3. Check the circuit diagram.
Check the circuit diagram for possible clues to the problem. Location of specific components in the circuit will help identify the source of the problem. Circuit diagrams are designed to make it easy to identify common points in circuits. This helps to narrow the problem to a specific area. For example, if several circuits fail at the same time,
check for a common power source or common ground connection (i.e., VREF, signal ground, actuator power, actuator ground). If part of a circuit fails, check the connections between the part that works and the part that
does not work. For example, if the low-beam headlights work, but both high-beam headlights and the high-beam indicator do not work, the power and ground paths must be good. Since the dimmer switch is the component that switches the power to the high-beam headlights, it is probably the cause of failure.
4. Determine the cause of the problem and follow diagnostic procedures in Section 7.
5. Make the repair.
Repair the problem circuit as directed in the diagnostic tables
6. Verify that the repair is complete.
Operate the system. Check that the repair has removed all symptoms and that the repair has not caused new symptoms.