If the application is equipped with two throttles, the
engine will use the second throttle until the fault is
repaired.
If a second throttle is not installed or if the second
throttle has a fault, the following conditions will occur:
• The engine will default to the limp home speed.
• If the engine speed is higher than the limp home
speed, the engine will decelerate to the limp home
speed.
• If the engine speed is lower than the limp home
speed, the engine speed will remain at the current
speed.
• The engine will remain at this speed while the
diagnostic code remains active.
• All inputs from the faulty throttle are ignored by the
ECM until the fault is repaired.
• All inputs from the repaired throttle will be ignored
by the ECM until the keyswitch has been cycled.
Check that the software configuration in the ECM is
correct for a multi-position throttle.
If the engine has an analog throttle with an Idle
Validation Switch (IVS), then refer to
Troubleshooting, “Idle Validation - Test”.
The throttle switch provides the operator with the
ability to select the desired engine speed. The throttle
switch configuration may be selected between 0 to 4
switches. A multi-position rotary switch may be used.
The throttle switch is typically connected to the four
throttle inputs of the ECM. Each position generates a
specific ON/OFF pattern on the throttle inputs. A
diagnostic code is generated if a pattern that does
not correspond with any of the switch positions is
detected.
Once a diagnostic code is generated, the ECM
ignores the throttle input signals. The desired engine
speed is set to low idle if no alternative throttle is
detected.
Voltage at the throttle inputs to the ECM should be
13.8 ± 0.5 VDC when the throttle inputs are open.
The voltage should be less than 0.5 VDC when the
throttle inputs are closed.
During the following procedure, refer to the electrical
schematic for the application.
Complete the procedure in the order in which the
steps are listed.
UENR4469-36 439
Circuit Tests
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