Page 363 - Understanding Automotive Electronics

2735 | CH 10 Page 350 Tuesday, March 10, 1998 1:27 PM

10 DIAGNOSTICS

code was set in memory. If 20 such cycles have occurred without a fault, this
counter is set to zero and all trouble codes are cleared.
Parameter 10 is a logical (binary) variable that indicates whether the
engine control system is operating in open or closed loop. A value of 1
corresponds to closed loop, which means that data from the O sensor is fed
2
back to the controller to be used in setting injector pulse duration. Zero for this
variable indicates open-loop operation, as explained in Chapters 6 and 7
Parameter 11 is the battery voltage minus 10. A decimal point is assumed
between the digits. Thus, 2.3 is read as 12.3 volts.
After completion of parameter data values, the climate control display will
advance to 95. The remaining codes are specific to certain Cadillac models and
are not germane to the present discussion.
Once the mechanic has read all of the fault codes, he or she proceeds with
the diagnosis using the shop manual in the same manner as explained for the
Cadillac example. For each fault code there is a procedure to be followed that
attempts to isolate the specific components that have failed. Obviously, the

Figure 10.11
Engine Data
Display

FPO

350 UNDERSTANDING AUTOMOTIVE ELECTRONICS