Application of multimeter to detect engine electronic control system
(1) Unless otherwise specified during the test process, pointer multimeters cannot be used to test computers and sensors. A high-impedance digital multimeter should be used. The internal resistance of the multimeter should not be less than 1OKΩ.
(2) First check the condition of fuses, fusible wires and terminal blocks, and then use a multimeter to check after troubleshooting these places.
(3) When measuring voltage, the ignition switch should be turned on (ON) and the battery voltage should not be lower than 11V.
(4) When using a multimeter to check a waterproof connector, you should carefully remove the leather cover. When inserting a test pen into the connector to check, do not apply excessive force to the terminal. During testing, the test leads can be inserted from the rear end with wiring or from the front end without wiring.
(5) When measuring resistance, gently shake the wire in the vertical and horizontal directions to improve accuracy.
(6) When checking for circuit breakage, you should first disconnect the connector between the computer and the corresponding sensor, and then measure the resistance between the corresponding terminals of the connector to determine whether there is a circuit break or contact failure.
(7) When checking the line for ground short circuit fault, the connectors at both ends of the line should be disassembled, and then the resistance value between the tested terminal of the connector and the vehicle body (ground) should be measured. If the resistance value is greater than 1MΩ, there is no fault.
(8) Before disassembling the engine electronic control system circuit, you should first cut off the power supply, that is, turn off the ignition switch (OFF), and remove the wiring on the battery pole.
(9) The symbol of the ground terminal on the connector varies depending on the vehicle model. Please refer to the maintenance manual to identify it.
(10) When measuring the voltage between two terminals or two lines, the two test leads of the multimeter (voltage range) should be in contact with the two terminals or two wires being measured.
(11) When measuring the voltage of a certain terminal or a certain line, the positive test lead of the multimeter should be in contact with the terminal or line being measured; and the negative test lead of the multimeter should be in contact with the ground wire.
(12) Checking the continuity of terminals, contacts or wires refers to checking whether the terminals, contacts or wires are energized but not disconnected. You can check the resistance value by measuring the resistance value of a multimeter.
(13) When measuring resistance or voltage, the connector is generally disassembled, thus dividing the connector into two parts. One part is called a sensor (or execution component) connector; the other part is called a sensor (or Actuator) wire harness connector or a sensor (or actuator) connector (or connector sleeve) on one side of the wire harness. For example, when you remove the connector on an injector, one part is called the injector connector and the other part is called the injector wire harness connector or the injector connector on one side of the wire. When measuring, you should figure out which part of the connector it is.
(14) All sensors, relays and other devices are connected to the computer, and the computer is connected to the actuator through wires, so when checking for faults, tests can be performed on the corresponding terminals of the computer connector.
