Cmp Circuit Operation - Navistar International DT 466 Diagnostic/Troubleshooting Manual

356 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS

CMP Circuit Operation

Figure 410 CMP circuit diagram
The ECM uses the CKP and CMP signal to calculate
engine speed and position. The CMP sensor provides
the ECM with a signal that indicates camshaft position.
The CMP contains a permanent magnet which
creates a magnetic field. The signal is created when
the camshaft peg rotates past the sensor breaking
the magnetic field. The ECM pins for the CMP sensor
are CMP positive X1-9 and CMP negative X1-10.
NOTE: Engine will not operate without CMP signal.
Fault Detection / Management
An inactive CMP signal during cranking is detectable
by the ECM. During engine cranking the ECM
monitors the CKP signal and Injection Control
Pressure (ICP) to verify the engine is rotating.
the CMP signal is inactive during this time a DTC
will be set. Electrical noise can also be detected
by the ECM. When the level is sufficient to effect
engine operation a corresponding DTC will be set. An
inactive CMP signal will cause a no start condition.
CMP Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
DTC 143
Incorrect CMP signal signature
• DTC 143 is set by the ECM when the CMP
transition occurs at the wrong CKP location.
• DTC 143 can be set due to a mistimed camshaft
to crankshaft, electrical noise in the CMP circuit,
or a failed CMP sensor.
DTC 145
CMP signal inactive
• DTC 145 is set by the ECM when CMP signal is
not detected while CKP signal is active or ICP has
increased.
If • DTC 145 can be set due to an open, short to
ground or open voltage source in the CMP circuit.
A failed CMP sensor can cause DTC 145 to be
set.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• Breakout Box
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.