Hyundai HL955 Manual page 112

3) 3)
DEFINITION OF OPERATING MODES DEFINITION OF OPERATING MODES
(1) (1)
Normal Normal
There's no failure detected in the transmission system or the failure has no or slight effects on
transmission control. TCU will work without or in special cases with little limitations. (See
following table)
(2) (2)
Substitute clutch control Substitute clutch control
TCU can't change the gears or the direction under the control of the normal clutch modulation.
TCU uses the substitute strategy for clutch control. All modulations are only time controlled.
(Comparable with EST 25)
(3) (3)
Limp-home Limp-home
The detected failure in the system has strong limitations to transmission control. TCU can
engage only one gear in each direction. In some cases only one direction will be possible.
TCU will shift the transmission into neutral at the first occurrence of the failure. First, the operator
must shift the gear selector into neutral position.
If output speed is less than a threshold for neutral to gear and the operator shifts the gear selector
into forward or reverse, the TCU will select the limp-home gear.
If output speed is less than a threshold for reversal speed and TCU has changed into the limp-
home gear and the operator selects a shuttle shift, TCU will shift immediately into the limp-home
gear of the selected direction.
If output speed is greater than the threshold, TCU will shift the transmission into neutral. The
operator has to slow down the vehicle and must shift the gear selector into neutral position.
(4) (4)
Transmission-shutdown Transmission-shutdown
TCU has detected a severe failure that disables control of the transmission.
TCU will shut off the solenoid valves for the clutches and also the common power supply (VPS1).
Transmission shifts to neutral. The park brake will operate normally, also the other functions
which use ADM1 to ADM8.
The operator has to slow down the vehicle. The transmission will stay in neutral.
(5) (5) TCU-shutdown TCU-shutdown
TCU has detected a severe failure that disables control of system.
TCU will shut off all solenoid valves and also both common power supplies (VPS1, VPS2). The
park brake will engage, also functions are disabled which use ADM 1 to ADM 8.
The transmission will stay in neutral.
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Abbreviations Abbreviations
OC : Open circuit
SC : Short circuit
OP mode : Operating mode
TCU : Transmission control unit
EEC : Electronic engine controller
PTO : Power take off
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