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

458 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS

ICP Circuit Operation

Figure 462 ICP circuit diagram
The ICP sensor is supplied a 5 V reference signal at
Pin 2 through valve cover gasket Pin B from ECM Pin
X1–14. The ICP sensor is supplied a signal ground at
Pin 1 through valve cover gasket Pin C from ECM Pin
X1–6. The ECM monitors the ICP signal from sensor
Pin 3 through valve cover gasket Pin A to ECM Pin
X1–20.
Fault Detection / Management
The ECM continuously monitors the signal of the ICP
sensor to determine if the signal is within an expected
range. If the ECM detects a voltage greater or less
than expected, the ECM will set a DTC, illuminate the
amber ENGINE lamp, ignore the ICP sensor signal,
and use a preset value based on engine operating
conditions.
ICP Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamps.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
DTC 124
ICP signal out-of-range low
• DTC 124 is set by the ECM if signal voltage is less
than 0.039 V for more than 0.1 second.
• DTC 124 can be set due to an open or short to
ground on the signal circuit, a failed ICP sensor
or an open V
• When DTC 124 is active the amber ENGINE lamp
is illuminated.
DTC 125
ICP signal out-of-range high
• DTC 125 is set by the ECM if the signal voltage is
greater than 4.9 V for more than 0.1 second.
• DTC 125 can be set due to a signal circuit shorted
to V
• When DTC 125 is active the amber ENGINE lamp
is illuminated.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
circuit or V
REF REF
or B+, or a failed ICP sensor.
REF
short to ground.