A typical electrical circuit may include an electrical component, various switches, relays, motors, fuses, fuses, or circuit breakers related to that component, as well as wiring and electrical connectors that connect the component to the battery and body ground. To facilitate the task of troubleshooting electrical circuits, circuit diagrams of electrical connections are attached at the end of the Manual.
Before you start troubleshooting any of the electrical circuits, carefully study the corresponding diagram in order to understand its functional purpose as clearly as possible. Narrowing the circle of troubleshooting is usually done by gradually identifying and eliminating normally functioning components of the same circuit. If several components or circuits fail at the same time, the most likely cause of the failure is a blown fuse or a ground fault (different circuits in many cases can be closed to one fuse or ground terminal).
Electrical equipment failures are often due to the simplest causes, such as terminal corrosion, fuse failure, fusible link burnout, or a defective switching relay. Perform a visual inspection of the condition of all fuses, wiring, and electrical connectors in the circuit before proceeding with more specific component testing.
In the case of using diagnostic tools for troubleshooting, carefully plan, in accordance with the attached electrical diagrams, at which points in the circuit and in what sequence the device should be connected in order to most effectively identify the defect.
Basic diagnostic tools include an electrical circuit tester or voltmeter (12 V pilot lamp can also be used with a set of connecting wires), indicator of the conductivity of the contour segment (probe), including a light bulb, its own power source and a set of connecting wires. In addition, you should always have in the car a set of cables for starting the engine from an auxiliary source, equipped with alligator clips and, preferably, a circuit breaker, which can be used to bypass and connect various electrical components during the circuit diagnostics. As mentioned above, before proceeding to check the circuit using diagnostic equipment, determine from the diagrams the place of its connection.
Checking for voltage
Voltage checks are made in the event of a malfunction of the circuit. Connect one of the circuit tester leads to either the negative battery post or a well grounded point on the vehicle body. Connect the other tester lead to the circuit's electrical connector terminal, preferably the one closest to the battery or fuse. If the control lamp on the tester lights up, there is voltage on this section of the circuit, which confirms the health of the circuit between this terminal and the battery. Continuing in a similar manner, explore the rest of the outline. The detection of a lack of voltage indicates the presence of a malfunction between this point of the circuit and the last one previously checked (where tension was present). In most cases, the failure is caused by loose electrical connections and poor contact quality.
Please note that some of the onboard electrical circuits are only energized in the ignition key positions «ACC» (Parking) or «RUN» (Movement).
Looking for a short circuit
One of the methods for searching for a short circuit is to remove the fuse and connect a probe lamp or voltmeter instead. There must be no voltage in the circuit. Pull the wiring while watching the probe lamp. If the lamp starts flashing, there is a short to ground somewhere in this harness, possibly caused by chafing of the wire insulation. A similar check can be made for each of the circuit components, including switches.
Grounding check
This test is made to determine the reliability of the grounding of the component. Disconnect the battery and connect one of the wires of the probe lamp equipped with an independent power source to a known well-grounded point. Connect the other lamp wire to the harness or terminal being tested. If the lamp lights up, ground is OK (and vice versa).
Conductivity Tests
The check is made in order to detect breaks in the electrical circuit. After turning off the power to the circuit, check it with a probe lamp equipped with an independent battery. Connect the probe wires to both ends of the loop (or to «power» end (+) and a well-grounded body point), if the control lamp lights up, there is no break in the circuit. Failure to turn on the lamp indicates a violation of the conductivity of the circuit. In the same way, you can check the health of the switch by connecting a probe to its terminals. When the switch is turned to position «On» the test lamp should light up.
Cliff localization
When diagnosing a suspect for an open circuit, visually detecting the cause of a malfunction turns out to be quite difficult, since inspecting the terminals for corrosion or a violation of the quality of their contacts is difficult due to limited access to them (usually the terminals are covered by the connector housing). A sharp twitch of the connector housing on the sensor or its wiring harness in many cases leads to the restoration of conductivity. Do not forget about this when trying to localize the cause of the suspect's failure to break the circuit. Intermittent failures can be caused by terminal oxidation or poor contact quality.
Diagnosing faults in electrical circuits is not at all a difficult task, provided it is clear that the current flows to all electrical loads (lamp, electric motor, etc.) from the battery through wires through switches, relays, fuses, fuses, and then returns to the battery through the vehicle ground. Any problems associated with the failure of electrical equipment can only be caused by the interruption of the supply of electric current to them from the battery or its return to it.