The following electrical wiring diagram applies for 1991 Lexus ES 250. This manual provides information on the electrical circuits in on vehicles by dividing them into a circuit for each system. The actual wiring of each system circuit is shown from the point where the power source is received from the battery as far as each ground point. All circuit diagrams are shown with the switches in the OFF position. When troubleshooting any problem, first understand the operation of the circuit where the problem was detected, the power source supplying power to that circuit, and the ground points. See the System Outline to understand the circuit operation.
When the circuit operation is understood, begin troubleshooting of the problem circuit to isolate the cause. Use Relay Location and Electrical Wiring Routing sections to find each part, junction block and wiring harness connectors, wiring harness and wiringharness connectors, splice points, and ground points of each system circuit. Internal wiring for each junction block is also provided for better understanding of connection within a junction block.