General concepts of electrical troubleshooting
The connection diagrams are in the electrical system sections; pay attention to these diagrams as they show the connector/component as viewed from the cable harness side, that is looking at the cables when going out of the "main" cable harness and into the connector/component.
Caution! Before carrying out any troubleshooting procedure on the vehicle, check that the battery voltage is above 12V.
Connector check procedure
The procedure includes the following checks:
1. Observation and check of the connector position on the component or on the coupling connector, making sure that the locking catch is released.
2. Observation of the terminals on the connector: no rust marks or dirt should be present and it is important to check terminal correct positioning on the connector (i.e., all terminals aligned at the same depth) and terminal integrity (i.e., that terminals are not loose, open/bent, etc.). For connectors whose terminals are not visible (e.g. Marelli control unit) use a metal cable of suitable diameter and introduce it carefully in the connector slot at the same depth as for the other terminals of the connector.
Caution! In case of temporal malfunctioning, carry out all due checks looking for fault by moving slightly the cable harness being inspected.
3. Pulling the cables slightly from the back of the connector in order to check the correct position of the terminals on the connector and of the cable on the terminal.
Continuity check
Check goal: this control is to check that there are not any circuit interruptions nor excessive resistance, for instance caused by rust, on the two terminals being inspected.
Tester: set the tester on the "continuity" symbol and place the tester probes on the two circuit ends: the tester emits a sound signal only if there is continuity; the tester can also be set to the Ohm symbol to check that the circuit resistance is null or a few tenths of an Ohm.
Caution! The circuit should not be energised, otherwise the test is irrelevant.
Ground connection check
Check goal: this control is to check if a cable or a circuit is in contact with the vehicle ground (-) connection.
Tester: set the tester on the "continuity" symbol and place one tester probe on the vehicle ground connection (or on the battery - terminal) and the other probe on the cable being inspected: the tester sends out a sound signal only if there is continuity. The tester can also be set to the Ohm symbol to check that the circuit resistance is null or a few tenths of an Ohm.
Caution! If there is a ground connection coming from the control unit, make sure that during the test the control unit is ground connected to the circuit.
Voltage check
Check goal: this control is to check if a cable is energised, i.e. if it receives power supply from the battery or the control unit.
Tester: set the tester on the direct current symbol and place the tester red probe on the cable being inspected and the black probe on the vehicle ground connection (or on the battery - terminal).
Caution! In case of temporal malfunctioning, carry out all due checks looking for fault by moving slightly the cable harness being inspected.