Precautions for testing engine electronic control

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Precautions for testing the engine electronic control system with a multimeter

(1) unless otherwise specified in the test process, the pointer multimeter cannot be used to test the computer and sensor. Instead, a high impedance digital multimeter should be used, and the internal resistance of the multimeter should not be less than 1ok

(2) first check the condition of fuses, fusible wires and wiring terminals, and then check them with a multimeter after troubleshooting these places

(3) when measuring the voltage, the ignition switch should be turned on (on), and the battery voltage should not be lower than 11V

(4) when checking the waterproof connector with a multimeter, carefully remove the leather cover and insert the test probe into the connector. Do not use too much force on the terminal when checking. During detection, the test probe can be inserted from the back 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 the accuracy

(6) when checking the circuit open circuit fault, disconnect the connector of the computer and the corresponding sensor first, and then measure the resistance between the corresponding terminals of the connector to determine whether there is an open circuit or poor contact fault

(7) when checking the ground short circuit fault of the line, disconnect the connectors at both ends of the line, and then measure the resistance between the tested terminal of the connector and the vehicle body (ground), especially to our zero based employees. If the resistance value is greater than 1m, there is no fault

(8) before disassembling the circuit of the engine electronic control system, first cut off the power supply, and the built-in plug-in card is inserted into the computer, that is, disconnect the ignition switch (off), and remove the wiring on the battery pole

(9) the symbol of the grounding terminal on the connector varies with the vehicle type, and attention should be paid to identifying it according to the maintenance manual

(10) when measuring the voltage between two terminals or between two lines, the multimeter should be used. Therefore, the major automobile brand industry said that only qualified materials can be used in automobile accessories (voltage range). The two probes of the two terminals or two wires measured contact

(11) when measuring the voltage of a terminal or a line, the positive probe of the multimeter should be in contact with the measured terminal or line; Contact the negative probe of the multimeter with the ground wire

(12) checking the continuity of terminals, contacts or wires refers to checking whether terminals, contacts or wires are powered on without disconnection, which can be checked by measuring their resistance with the resistance gear of a multimeter

(13) when measuring resistance or voltage, the connector is generally disassembled, so the connector is divided into two parts, one of which is called a sensor (or actuator) connector; The other part is called a sensor (or actuator) wiring harness connector or a sensor (or actuator) connector (or connector sleeve) on one side of the wiring harness. For example, after removing the connectors on the fuel injector, one part is called the fuel injector connector, and the other part is called the fuel injector wire harness connector or the fuel injector connector on one side of the wire. When measuring, it should be clear which part of the connector is

(14) all sensors, relays and other devices are connected to the computer, and the computer is connected to the executive parts through wires, so when checking the fault, you can test on the corresponding terminal of the computer connector

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