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Inspection connections
A WARNING When checking the control module Motronic 4.3, do not remove it from the car as long as the main switch does not disconnect the power supply. This occurs within 150 seconds after the ignition is switched off. |
| Fig. 10.4. Check the plug connector
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When all the measurements and inspections, accompanied by the separation of the connectors, be sure to examine the findings of the connector (Fig. 10.4). Check each plug and socket for the presence of the oxidation of both the connecting portion, and sealing the wires. Oxidation is unacceptable. Make sure the plugs and sockets are not damaged and are securely fastened to the connector, the conductors are securely connected to the plugs / sockets. Pay particular attention to plugs and jacks belonging to a chain, which registered a fault. Check for loose individually each plug and socket in the connector housing. With a slight twitch, they should remain in place.
Open circuit
In the open circuit indicates Failure of the electrical signal from the device to the sending device receives his or distortion of the output signal parameters. Usually the cause of a problem is a worn-out, disconnect the wiring or oxides. This usually occurs in the connectors and sealing wire. To check the wires that are part of the tested circuits, remove the connectors on both ends of the wire.
| Fig. 10.5. Check for open circuit using ohmmeter
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Connect an ohmmeter to both ends of the wires (Fig. 10.5) and measure the resistance of the absence of a wire break meter should read 0 ohms. Be sure to check for the control module and the connector box control modules bent or damaged plugs or sockets, as this defect can cause malfunction. Be particularly careful to check the plugs and sockets belonging to the chain, which registered a fault. Here are some faults that you may encounter when testing:
Short circuit on "weight"
Short circuit between the current carrying conductor and "weight" usually leads to the circuit fuse to blow, or a violation of any of the function (or functions). To verify: 1) Turn on all the switches and activate all sensors circuit to check whether the fuse burns out; 2) Disconnect the circuit components, so they did not affect the results of measurements; 3) Using an ohmmeter, measure the resistance between the wire and "weight"; 4) the absence of the components in the chain of the device should show "infinite" resistance; 5) carefully check the plugs and jacks belonging to a chain, which registered a fault.
Short circuit on the current-carrying conductor
Short-circuiting the wires to another current-carrying wire is usually causes a blown fuse or unplanned operation of a system. To verify:
| Fig. 10.6. Detection circuit short-circuit current-carrying wire
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1) Use a voltmeter to measure the voltage at various points in the circuit (Fig. 10.6), including with the switches and cycling sensors. The voltage shown by the voltmeter depends on the circuit where the measurement is made, as well as the position of the switches and the state of the sensors. Average for the circuit voltage is provided in the electric circuit; 2) If you plan to short-circuit between the wires, measure the resistance between them with an ohmmeter. The ohmmeter should show "infinite" resistance between wires not connected to each other in the chain; 3) carefully check the plugs and jacks belonging to a chain, which registered a fault;
Increased contact resistance due to oxidation
Theoretically, the resistance of connectors, wires and conclusions should be 0 ohms. However, some resistance is always present due to wear and oxidation conclusions. If the resistance becomes excessively large, the operation system is disturbed. The magnitude of the contact resistance, which interferes with the functioning of the system depends upon the load circuit. Typically, this value is a few ohms.
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