320 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
BCP Circuit O peration
Figure 387 BCP circuit diagram
TheBCPsensorissuppliedwitha5Vreferencesignal
at Pin 2 through the valve cover gasket Pin B from
ECM Pin X1–14. The BCP sensor is supplied a signal
ground at Pin 1 through the valve cover gasket Pin C
from ECM Pin X1–6. The BCP sensor sends a signal
from sensor Pin 3 through valve c over g a sket Pin A to
ECM Pin X2–11.
Fault Detection / Management
The ECM continuously monitors the signal of the BCP
sensor to determine if the signal is within an expecte d
range. If the ECM detects a voltage greater or less
than expected, the ECM will se t a DTC an d illuminate
the amber ENGINE lamp.
BCP Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamps.
DTC 126
BCP signal out-of-range low
• DTC 126 is set by the ECM if signal voltage is less
than 0.039 V for more than 0.35 second.
• DTC 126 can be set due to an open or short to
ground on the sig na l circuit, a failed BCP sensor,
an open V
REF
circuit or V
REF
short to ground.
• When DTC 126 is active the amber ENGINE lamp
is illuminated.
DTC 127
BCP signal out-of-range high
• DTC 127 is set by the ECM if the signal voltage is
greater than 4.9 V for more than 0.35 second.
• DTC 127 can be set due to a signal c ircuit shorted
to V
REF
or B+, or a failed BCP sensor.
• When DTC 127 is active the amber ENGINE lamp
is illuminated.
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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