70 KENR9126
Troubleshooting Section
g01365757
Illustration 14
Example of the typical operating range of a sen sor
(1) This area represents the no rmal operating range of the engine
parameter.
(2) In these areas, the engine is operating in an unsafe operating
range of the monitored param eter. A n event code will be
generated for the m onitored parameter. The sensor circuit
does not ha ve an electronic problem . R efer to Troubleshooting,
“Troubleshooting with an Event Code” for additional information
on event codes.
(3) In these areas, the signal from the sensor is outside of the
operating range o f the sensor. The sensor circuit has an
electronic problem. A diagnostic code will be generated for
the sensor circuit.
Active Diagnosti c Codes
An active diagnostic code represents a problem with
the electronic control system. Correct the problem
as soon as possible.
When the ECM generates an active diagnostic code
and the diagnostic lamp is activated in order to alert
the operator . If the condition that generated the code
is momentary, the message disappears from the
list of active diagnostic codes. The diagnostic code
becomes logged.
Logged D iagnostic Codes
When the ECM generates a diagnostic code, the
ECM logs the code in permanent memory. The
ECM has an internal diagnostic clock. Each ECM
willrecordthefollowinginformationwhenacodeis
generated:
•
The hour of the first occurrence of the code
•
The hour of the last occurrence of the code
•
The number of occurrences of the code
This information is a valuable indicator for
troubleshooting intermittent problems.
A code is cleared from memory when one of the
following conditions occur:
•
The service technician manually clears the code.
•
The code does not recur for 100 hours.
•
A new code is logged and there are already ten
codes in memory. In this case, the oldest code is
cleared.
Some diagnostic codes may be easily triggered.
Some diagnostic codes may log occurrences that
did not result in complaints. The most likely cause
of an intermittent problem is a faulty connection
or damaged wiring. The next likely cause is a
component failure. The least likely cause is the failure
of an electronic module. Diagnostic codes that are
logged repeatedly may indicate a problem that needs
special investigation.
Note: Always clear logged diagnostic codes after
investigating and correcting the problem which
generated the code.
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