Aps/Ivs Circuit Operation - Navistar International DT 466 Diagnostic/Troubleshooting Manual

7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS

APS/IVS Circuit Operation

Figure 376 APS/IVS circuit diagram
The APS/IVS are integrated into one component
and mounted on the pedal. The accelerator pedal
assembly is serviceable to the extent that the APS/IVS
switch can be replaced without replacing the complete
assembly.
The ECM determines the accelerator pedal position by
processing input signals from the APS and the IVS.
The accelerator pedal position is one of the controlling
variables in the calculation of desired injection control
pressure.
APS
The ECM supplies a regulated 5 V signal from ECM
chassis connector Pin X4–4 to APS connector Pin C.
The APS returns a variable voltage signal (depending
on pedal position) from the APS connector Pin A to
ECM Pin X4–18. The APS is grounded at Pin B from
the ECM Pin X4–24.
APS Auto-Calibration
The ECM learns the lowest and highest pedal
positions by reading and storing the minimum and
maximum voltage levels from the APS. In this manner
the ECM auto-calibrates the system to allow maximum
pedal sensitivity. The ECM auto-calibrates as the
ignition switch is on, but when the ignition switch is
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
turned OFF, these values are lost. When the key is
turned on again, this process starts over. When the
pedal is disconnected (or a new one is installed),
the pedal does not need to be calibrated. It simply
auto-calibrates the new pedal assembly whenever
the key is turned on again.
IVS
The ECM expects to receive one of two signals
through the ECM chassis connector Pin X4–12 from
APS/IVS connector Pin D:
• 0 V when the pedal is at the idle position.
• B+ when the pedal is depressed
The IVS receives a 12 V ignition voltage at Pin F from
the ignition fuse in the power distribution box. When
the pedal is not in the idle position (throttle applied),
the IVS supplies a 12 V signal to the ECM.
The ECM compares APS/IVS inputs to verify when
the pedal is in the idle position. If the APS signal
at Pin X4–18 indicates throttle is being applied, the
ECM expects to see 12 V at the IVS. If the APS signal
indicates throttle is not applied, the ECM expects
to see 0 V at the IVS. The timing process is critical
between the APS and IVS sensors. For this reason, it
is very difficult to determine if the APS/IVS assembly
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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