Multi-meter test method for automobile engine electronic control system

In winter, when the car engine is difficult to start, there are often electronic control system failures. Here are several methods of testing the multimeter.

1, resistance measurement method

After the multimeter switch is turned to the proper position of the resistance (Ω) and calibrated, the resistance value can be measured. The technical status of many electrical devices on automobiles can be judged by the method of detecting the resistance value, such as checking the open circuit and short circuit of electrical components and lines.

2, DC voltage measurement method

Turn the switch to the DC voltage (V range) (choose the appropriate range) and connect the test leads to both ends of the test. The method of measuring the voltage can be used to check the voltage (signal voltage or supply voltage) at each point on the circuit and the voltage drop across the electrical components.

3, open circuit (open circuit) detection method

If there is wire breaking malfunction, the method can be "checked on" or "Check voltage" to determine the disconnection portion.

"Check on" Method:

(1) Disconnect connectors B and C and measure the resistance between them. If the resistance value between connector A terminal 1 and connector C terminal 1 is ∞, they will not conduct (break); if the resistance value between connector A terminal 2 and connector C terminal 2 is 0 Ω , between them conduction (no break).

(2) release connector, measuring the resistance value between the connectors A and B, B and C. If the resistance value between terminal 1 of connector A and terminal 1 of connector B is 0 Ω, and the resistance between terminal 1 of connector A and terminal 1 of connector B is ∞, then terminal 1 of connector A There is continuity between the terminal 1 of the connector B and the terminal 1 of the connector C and the terminal 1 of the connector C.

"Check voltage" method:

In circuits where voltage is applied to the terminals of a computer connector, an "inspection voltage" method can be used to check the open circuit fault. When the connectors are connected, in the circuit where the computer output terminal voltage is 5V, measure the terminals 1 of the connector A, the terminals 1 of the connector B, the terminals 1 of the connector C, and the body (ground) When the measured voltage is 5V, 5V, and 0V, it can be determined that the wiring between B's terminal 1 and C's terminal 1 has an open circuit fault.

4, short circuit inspection method

If the wiring is short-circuited to the ground, it can be determined by checking whether the wiring and the body (or ground) are conducting.

(1) Disconnect connectors A and C and measure the resistance between terminals 1 and 2 of the connector A and the body. If the measured resistance values ​​are 0Ω and ∞, respectively, there is a short-circuit ground fault between the wiring of terminal 1 of connection A and terminal 1 of connector C and the body.

(2) Disconnect connector B and measure the resistance between terminal 1 of connector A and terminal 1 of connector C and body (ground). If the measured resistance values ​​are ∞ and 0Ω, respectively, it can be determined that there is a short-circuit ground fault between the wiring between the terminal 1 of the connector B and the terminal 1 of the connector C and the vehicle body.

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