
RENR5622 21
Troubleshooting Section
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Illustration 11
Output voltage from a typical analog temperature sensor
Illustration 11 indicates the signal range for a typical
analog sensor. Diagnostic codes will be generated if
the sensor’s output signal is below 0.2 VDC or above
4.8 VDC.
Note: This graphic is an example. The ranges in this
graphic are examples.
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 engine’s ECM generates an active
diagnostic code, the “Active Alarm” indicator (“Engine
Control Alarm Status” on Cat ET) 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 Diagnostic 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.
i02415088
Event Cod
eList
SMCS Code: 1901
Cross-Reference Information for
Event Codes
Table 6 i
s a list of the event codes for the engine.
The event codes are cross-referenced with the
appropriate functional test or the procedure that can
be used t
o troubleshoot the code.
Event codes are generated when abnormal operating
conditi
ons exist. A further explanation of event codes
and the engine’s monitoring system are described
after Table 6.