Ford Taurus, Руководство пользователя

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some electronic engine control systems. Some tach/dwell meters are powered by
an internal battery, while others take their power from the vehicle battery in use.
The internal battery powered testers usually require calibration much like an
ohmmeter before testing.
Special Test Equipment
A variety of diagnostic tools are available to help troubleshoot and repair
computerized engine control systems. The most sophisticated of these devices are
the console type engine analyzers that usually occupy a garage service bay, but
there are several types of aftermarket electronic testers available that will allow
quick circuit tests of the engine control system by plugging directly into a special
connector located in the engine compartment or under the dashboard. Several
tool and equipment manufacturers offer simple, hand held testers that measure
various circuit voltage levels on command to check all system components for
proper operation. Although these testers often cost about $300-$500, consider
that the average computer control unit can cost just as much and the money
saved by not replacing perfectly good sensors or components in an attempt to
correct a problem could justify the purchase price of a special diagnostic tester
the first time it's used.
These computerized testers can allow quick and easy test measurements while
the engine is operating or while the vehicle is being driven. In addition, the on-
board computer memory can be read to access any stored trouble codes, in effect
allowing the computer to tell you "where it hurts" and aid trouble diagnosis by
pinpointing exactly which circuit is malfunctioning. In the same manner, repairs
can be tested to make sure the problem has been corrected. The biggest
advantage these special testers have is their relatively easy hookups that
minimize or eliminate the chances of making the wrong connections and getting
false voltage readings or damaging the computer accidentally.
It should be remembered that these testers check voltage levels
incircuits; they don't detect mechanical problems or failed components.
Testerssimply can inform you if the circuit voltage falls within the pre-
programmedlimits stored in the tester PROM unit. Also, most of the hand
held testers aredesigned to work only on one or two systems made by a
specific manufacturer.
A variety of aftermarket testers are available to help diagnose different
computerized control systems. Owatonna Tool Company (OTC), for example,
markets a device called the OTC Monitor which plugs directly into the Assembly
Line Diagnostic Link (ALDL). The OTC tester makes diagnosis a simple matter of
pressing the correct buttons and, by changing the internal PROM or inserting a
different diagnosis cartridge, it will work on any model from full size to
subcompact, over a wide range of years. An adapter is supplied with the tester to
allow connection to all types of ALDL links, regardless of the number of pin
terminals used. By inserting an updated PROM into the OTC tester, it can be
easily updated to diagnose any new modifications of computerized control
systems.
Wiring Harnesses
The average vehicle contains about
1
/
2
mile (0.805 km) of wiring, with hundreds
of individual connections. To protect the many wires from damage and to keep
them from becoming a confusing tangle, they are organized into bundles,
enclosed in plastic or taped together and called wiring harnesses. Different wiring
Стр . 10 из 16 UNDERSTANDING AND TROUBLESHOOTING ELECTRICAL SYSTEMS
18.11.2005 http://www.chiltondiy.com/content/8687/8687_6_1.html