7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 509
MAT Circuit Operation
Figure 489 MAT circuit diagram
TheMATsensorissuppliedwitha5Vreference
voltage at Pin 2 from ECM Pin X2–14. The sensor
is grounded at Pin 1 through the signal ground at
ECM Pin X1–6. As the air temperature increases
or decreases, the sensor changes resistance and
provides the air temperature signal voltage at the
ECM. The signal voltage is monitored by the ECM to
determine the temperature of the air.
Fault Detection / Management
The ECM continuously monitors the signal of the MAT
sensor to determine if the signal is within an expected
range. If the ECM detects the signal voltage is greater
or less than expected, the ECM will set a DTC.
MAT Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
DTC 161
MAT signal out-of-range low
• DTC 161 is set by the ECM when the s ignal
voltage is less than 0.098 V for more than 0.35
second.
• DTC 161 can be set due to a short to ground in
the signal circuit or a failed M AT sensor.
• When DTC 161 is active the amber ENGINE lamp
is illuminated.
DTC 162
MAT signal out-of-range high
• DTC 162 is set by ECM when the signal voltage
is greater than 4. 58 V for more than 0.35 se cond.
• DTC 162 can be set due to an open signal or
ground circuit , short to a voltage source, or a
failed M AT sensor.
• When DTC 162 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
• Breakout Box
• Breakout Harness
• Terminal Te st Adapter Kit
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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