Toyota Corolla Repair Manual: Check open circuit

Toyota Corolla Repair Manual / Introduction / How to troubleshoot ecu controlled systems / Electronic circuit inspection procedure / Check open circuit

For the open circuit in the wire harness in fig. 1, Perform a resistance check in step (b) or a voltage check in step (c) to locate the section.

Check the resistance.

Disconnect connectors a and c and measure the resistance between them.

Resistance: 1 Ω or less

Hint

: measure the resistance while lightly shaking the wire harness vertically and horizontally. In the case of fig. 2: Between terminal 1 of connector a and terminal 1 of connector c " 10 kΩ

or higher between terminal 2 of connector a and terminal 2 of connector c " below 1 Ω

therefore, the cause is an open circuit between terminal 1 of connector a and terminal 1 of connector c.

Disconnect connector b and measure the resistance between the connectors.
In the case of fig. 3: Between terminal 1 of connector a and terminal 1 of connector b1 " below 1 w between terminal 1 of connector b2 and terminal 1 of connector c " 10 kw therefore, the cause is an open circuit between terminal 1 of connector b2 and terminal 1 of connector c.

Check the voltage.

In a circuit in which voltage is applied (to the ecu connector terminal), an open circuit can be checked by conducting a voltage check.
As shown in fig. 4, With each connector still connected, measure the voltage between the body ground and terminal 1 of connector a at the ecu 5 v output terminal, terminal 1 of connector b, and terminal 1 of connector c, in that order.
If the results are: 5 v: between terminal 1 of connector a and body ground 5 v: between terminal 1 of connector b and body ground 0 v: between terminal 1 of connector c and body ground therefore, the cause is an open circuit in the wire harness between terminal 1 of connector b and terminal 1 of connector c.

Check short circuit

Basic inspection

Resistance measuring condition of electronic parts unless stated, all resistance is measured at an ambient temperature of 20 c (68 °F). As the resistance may be outside the specifi ...

Check short circuit

If the wire harness is ground shorted as shown in fig. 5, Locate the section by conducting a resistance check with the body ground in step (b). Check the resistance with the body grou ...

Other materials:

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