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7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
MAP Circuit Operation
Figure 484 MAP circuit diagram
The MAP sensor is supplied with a 5 V reference
voltage at Pin 2 from ECM Pin X1–14. The MAP
sensor is grounded at Pin 1 from ECM Pin X1–6. The
MAP sensor returns a variable voltage signal from Pin
3 to ECM Pin X2–3.
Fault Detection / Management
The ECM will ignore the MAP signal when the signal
is detected to be out of range or an incorrect value is
read. The engine will continue to operate based on
estimated values.
MAP Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
DTC 121
Intake MAP signal out-of-range high
•
DTC 121 is set by the ECM when the MAP signal
is greater than 4.9 V for more than 0.4 second.
•
DTC 121 can be set due to a signal circuit short
to V
or B+ or a failed MAP sensor.
REF
•
When DTC 121 is active the amber ENGINE lamp
is illuminated.
DTC 122
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Intake MAP signal out-of-range low
•
DTC 122 is set by ECM when the MAP signal is
less than 0.039 V for more than 0.4 second.
•
DTC 122 can be set due to an open or short to
ground on the signal circuit, a failed MAP sensor
or an open V
•
When DTC 122 is active the amber ENGINE lamp
is illuminated.
DTC 123
Intake MAP signal in-range fault
•
DTC 123 is set by ECM when the MAP signal is
greater than 115 kPa (17 psi) absolute at low idle.
•
DTC 123 can be set due to a restricted or plugged
sensor inlet, open signal ground, V
voltage source above 5.5 V, biased circuit, or a
failed MAP sensor.
•
When DTC 123 is active the amber ENGINE lamp
is illuminated.
Tools
•
EST with MasterDiagnostics® software
•
EZ-Tech® interface cable
•
Digital Multimeter (DMM)
•
3-Banana Plug Harness
•
500 Ohm Resistor Harness
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
circuit or V
short to ground.
REF
REF
REF
501
shorted to
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