522 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Tachometer Output Circuit
Figure 496 Function diagram for the tachometer output circuit
The function diagram for the tachometer output circuit
consists of the following:
• Remote tachometer
• Electronic Control Module (ECM)
• Camshaft Position (CMP) sensor
• Crankshaft Position (CKP) sensor
The E CM provides an output for a remote tachometer
with a 0 V to 12 V digital signal that indicates engine
speed. The frequency sent by the ECM is 1/5th of the
actual engine rpm (12 pulses per engine revolution).
Tachometer Input Signal
The ECM receives a signal from the CMP s ensor and
calculates engine speed (rpm). The ECM sends the
calculated engine speed as a digital buffered TACH
signal from the ECM connector to the owner installed
tachometer.
Tachometer Diagnostic Trouble Codes (DTCs)
DTCs are not available for communication between
the ECM and the remote tachometer.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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