Application of multimeter to test engine electronic control system
(1) Unless otherwise specified during the test, the computer and sensors should not be tested with a pointer multimeter, and a high impedance digital multimeter should be used, with an internal resistance of not less than 1 OKΩ.
(2) Check the condition of fuses, fusible wires and terminals first, and then use the multimeter after eliminating faults in these places.
(3) When measuring the voltage, the ignition switch should be on (ON) and the battery voltage should be not less than 11V.
(4) When checking the waterproof type connector with the multimeter, the holster should be removed carefully and no excessive force should be applied to the terminal when inserting the test pen into the connector for inspection. When testing, the test meter pen can be inserted from the rear end with wiring or from the front end without wiring.
(5) Gently shake the wires in vertical and horizontal directions when measuring resistance to improve accuracy.
(6) When checking for line break faults, disconnect the connectors of the computer and the corresponding sensors, and then measure the resistance between the corresponding terminals of the connectors to determine whether there is a break or a contact safety fault.
(7) When checking the line hitch short-circuit fault, you should disengage the connectors at both ends of the line, and then measure the resistance value between the connector's measured terminals and the body (hitch). Resistance value greater than 1MΩ for no fault.
(8) before removing the engine electronic control system line, you should first cut off the power supply, that is, the ignition switch is disconnected (OFF), remove the battery pole stakes on the wiring.
(9) The symbol of the ground terminal on the connector is different depending on the model, and you should pay attention to the maintenance manual to identify.
(10) When measuring the voltage between two terminals or two lines, the two pens of the multimeter (voltage) should be in contact with the two terminals or two wires to be measured.
(11) When measuring the voltage of a terminal or a line, the positive pen of the multimeter should be in contact with the measured terminal or line; and the negative pen of the multimeter should be in contact with the ground.
(12) Checking the conductivity of terminals, contacts or wires, etc. means checking whether the terminals, contacts or wires, etc. are energised without being disconnected, which can be checked by measuring their resistance values with the resistance gear of the multimeter.
(13) In measuring resistance or voltage, the connector is generally removed, so that the connector is divided into two parts, one of which is called a sensor (or executive part) connector; the other part is called a sensor (or executive part) wire bundle connector or wire bundle side of a sensor (or executive part) connector (or connector sleeve). For example, after removing the connector on the injector, one part is called the injector connector and the other part is called the injector wire bundle connector or the injector connector on the wire side. When measuring, figure out which part of the connector it is.
(14) All sensors, relays and other devices are connected to the computer, which in turn is connected to the actuating parts by wires, so when checking for malfunctions, you can test on the corresponding terminals of the computer connector.
