Ford Corsar Repair Manual page 190

TROUBLE DIAGNOSES
- 1
Sensors
Control unit Actuators
SEF232G
S E F 2 3 4 G
How to Perform Trouble Diagnoses for Quick
and Accurate Repair
INTRODUCTION
The engine has an electronic control unit to control major sys-
tems such as fuel control, ignition control, idle speed control,
etc. The control unit accepts input signals from sensors and
instantly drives actuators. I t is essential that both kinds of signals
are proper and stable. At the same time, it is important that
there are no conventional problems such asvacuum leaks, fouled
spark plugs, or other problems with the engine.
It is much more difficult to diagnose a problem that occurs
intermittently rather than continuously. Most intermittent
problems are caused by poor electric connections or faulty
wiring. In this case, careful checking of suspicious circuits may
help prevent the replacement of good parts.
A visual check only may not find the cause of the problems.
A road test with a circuit tester connected to a suspected circuit
should be performed.
Before undertaking actual checks, take just a few minutes to
talk with a customer who approaches with a driveability com-
plaint. The customer is a very good supplier of information on
such problems, especially intermittent ones. Through the talks
with the customer, find out what symptoms are present and
under what conditions they occur.
Start your diagnosis by looking for "conventional" problems
first. This is one of the best ways to troubleshoot driveability
problems on an electronically controlled engine vehicle.