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Fault diagnosis onboard electric equipment - the general information
Procedures and codes of diagnostics of electronic control systems discussed in Chapter Electric engine.
The structure of a typical electric circuit may include an electrical component, a variety of switches, relays, motors, fuses, fuses or circuit breakers that are relevant to this component, as well as wiring and electrical connectors that serve to connect the component to the battery and chassis ground. To facilitate the task of troubleshooting electrical circuits at the end of the Guidelines attached schematic diagrams of electrical connections.
Before starting to work on troubleshooting any of the electrical circuits, read the appropriate scheme to ensure that as clearly as possible to imagine its functional purpose. Narrowing the range of troubleshooting is usually done at the expense of the progressive identification and elimination of well-functioning components of the same circuit. With the simultaneous failure of several component or circuit most likely cause of failure is a blown fuse or a violation of the relevant ground (various contours in many cases close to one fuse terminal or mass).
Electrical failure is often explained by simple reasons, such as corrosion of the terminals, the failure of fuse burning fuse or defective relay switch. Perform a visual check of the status of all fuses, wiring and electrical connectors circuit before embarking on a more specific check of serviceability of its components.
In the case of applications for troubleshooting diagnostic tools, plan carefully in accordance with the wiring diagrams in any point of the circuit and the sequence in which the device must be connected with the aim of identifying the most effective defect.
The main diagnostic devices include electrical circuits tester or voltmeter (can also be used in the warning lamp 12 with a set of connecting wires), an indicator of the conduction path length (probe), which includes a light bulb, its own power supply and a set of connecting wires. Furthermore, one should always have a set of cables in the vehicle to start the engine from the auxiliary source equipped with alligator clips and preferably interrupter circuit which can be used for bridging and connecting various electrical components in diagnostic circuit. As mentioned above, before proceeding to the verification of the circuit using the diagnostic equipment, determine the schemes of his place of connection.
Checking voltage
Check availability of the voltage produced in the event of malfunction of the circuit. Connect one of the wires in the electrical circuits of the tester or to the negative pole of the battery or to a well-grounded point of the car body. Another wire tester connected to the terminal of the electric connector circuit, preferably next to the battery or fuse. If the warning lamp on the tester lights up, the voltage on this segment of the chain takes place, confirming serviceability of the circuit between the terminal and the battery. Continuing to operate in a similar manner, explore the rest of the circuit. Detection of absence of voltage indicates a fault between a given point of the circuit and the last of the previously tested (where the voltage is present). In most cases, the cause of failure is a weakening of the electrical connections and the violation of the quality of contacts.
 | Remember that power some of the contours of an onboard electric equipment is supplied only in the ignition key position "ACC" (parking) or ?�RUN?� (Movement). |
The search for short circuit
One method of searching is to extract short-circuit fuse and connection instead lamp or voltmeter probe. The voltage in the circuit should be absent. Pod?�rgayte wiring, watching the lamp-sampler. If the lamp flashes, somewhere in the harness has a short to ground, possibly caused by rubbing the wire insulation. A similar test can be performed for each of the components of the circuit, including the switches.
Check of earthing
This test is performed to determine the reliability of the ground component. Disconnect the battery and connect one wire-equipped self-powered lamp probe grounded to a known good point. Another lamp wire to connect the wiring or the terminal under test. If the lamp lights up, grounding in the order (and vice versa).
Check for conductivity
Checks are made to identify the continuity circuit After a power circuit, check it with a lamp-sampler equipped with autonomous battery. Connect the probe to both ends of the circuit (or "force" the end of the (+) and a well-grounded point of the body), if the warning lamp lights up, there is no break in the circuit. Disclaimer turn on the lamp indicates a violation of the conduction circuit. Similarly, the same way you can check the power switch and connecting the probe to the terminals. While translating the switch in the "On" indicator lamp should light up-sampler.
Localization cliff
In the diagnosis of a suspect for an open circuit to visually detect the cause of the problem is rather difficult, as inspection terminals for corrosion or violation of the quality of their contacts is hindered due to the limited access to them (normally closed terminal connector housing). Sudden twitching body connector on the sensor or its wiring harness in many cases leads to the restoration of conductivity. Keep this in mind when trying to localize the causes of failure of a suspect for an open circuit. Unstable occurring failures can be caused by oxidation of terminal or violation of the quality of contacts.
Troubleshooting of electrical circuits is not intractable problem, provided a clear idea of what current is supplied to all electrical loads (lamp, motor, etc.) from the battery through the wires through switches, relays, fuses, fusible links, and then It returns to the battery via the vehicle weight. Any problems associated with electrical failure can have their cause only the outage on their electric current from a battery, or return it to her.
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