Navistar International DT 466 Diagnostic/Troubleshooting Manual page 306

302 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
is working correctly when using a Digital Multimeter
(DMM).
Fault Detection / Management
When the key is on, the ECM continuously monitors
the APS/IVS circuits for expected voltages. It also
compares the APS and IVS signals for conflict. If
the signals are not what the ECM expects to see,
Diagnostic Trouble Codes (DTCs) will be set.
Any detected malfunction of the APS/IVS sensor
circuit will illuminate the amber ENGINE lamp.
the ECM detects an APS signal Out of Range HIGH
or LOW, the engine will ignore the APS signal and
operate at low idle. If a disagreement in the state of
IVS and APS is detected by the ECM and the ECM
determines that it is an IVS fault, the ECM will only
allow a maximum of 50% APS to be commanded. If
the ECM cannot discern if it is an APS or IVS fault,
the engine will be allowed to operate at low idle only.
APS/IVS Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
NOTE: If multiple APS/IVS DTCs are present, verify
the APS/IVS part number is correct for the specific
vehicle model.
NOTE: If elevated low idle rpm is experienced after
replacing the pedal assembly or APS/IVS sensor, and
there are no DTCs present, check pedal assembly or
APS/IVS sensor part numbers for correctness.
DTC 131
APS signal out-of-range low
• DTC 131 is set if the ECM detects voltage less
than 0.147 V. The ECM will then restrict engine
speed to idle.
• DTC 131 can be set due to a short to ground or
an open V or signal circuits. If the condition
REF
causing DTC 131 is intermittent and the condition
is no longer present, the code will become inactive
and normal engine operation will resume.
• When DTC 131 is active the amber ENGINE lamp
is illuminated.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
DTC 132
APS signal out-of-range high
• DTC 132 is set if the ECM detects a voltage
greater than 4.55 V. The ECM will then restrict
engine speed to idle.
• DTC 132 can be set due to a short to V
the APS signal circuit.
• When DTC 132 is active the amber ENGINE lamp
is illuminated.
If
DTC 133, 134, and 135
• The ECM checks the voltage output of the APS
by comparing the APS signal to the IVS signal.
APS and IVS signals can disagree in the following
situations:
•
•
DTC 133
APS in-range fault
• If the IVS signal is changing and the APS signal
is constant, the ECM assumes the APS is the
conflict source and sets DTC 133. The engine
rpm is restricted to idle.
• When DTC 133 is active the amber ENGINE lamp
is illuminated.
DTC 134
APS signal and IVS disagree
• If neither the APS or IVS is changing, or both are
changing, or the ECM cannot determine the DTC
in specified time, DTC 134 is set and engine rpm
is restricted to idle.
• When DTC 134 is active the amber ENGINE lamp
is illuminated.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
The APS signal indicates the pedal is pressed
down to accelerate, but the IVS signal
indicates idle position.
The APS signal indicates the pedal has been
released to allow the engine to return to idle,
but the IVS signal indicates off-idle position of
the pedal.
If the ECM detects either of the above
conditions, the ECM attempts to isolate
the source of conflict and set a DTC.
or B+ in
REF