Daewoo Korando. Manual - part 255

AUTOMATIC TRANSMISSION 5A-63

Figure 6.1.1 - Wiring Loom Pins

5A-64 AUTOMATIC TRANSMISSION

Default Transmission Operating Modes

The TCU relies on accurate information from its inputs and complete control of its outputs to effectively control the
transmission. To ensure that it has both valid inputs and functioning outputs, the TCU carries out both hardware and
software fault detection routines. The TCU will respond to any faults detected by adopting the operating modes which
are detailed below.

The following symptoms of faults are the most obvious results of each fault under ‘normal’ conditions.

There is always the possibility that a fault may not be detected. If undetected fault conditions are present, the
operation of the transmission is difficult to predict.

1 Throttle Fault

All shifts will occur as if a nominal throttle (approx. 44%) were applied for shift scheduling.

All shifts will be firm as full throttle and hence high engine torque is assumed.

The torque converter will be unlocked at all times.

All downshifts initiated by the shift lever will occur as though they were ‘automatic’ shifts. That is the engine

braking effect will not occur until near the end of the shift.

Line pressure will always stay high (solenoid 6 OFF) to cope with assumed high throttle/torque.

If a fault is undetected, the percent throttle is most likely to be interpreted as higher than actual, resulting in late
upshifts, early downshifts, firm shifting and a harsh 3-1 shift when stopping.

2 Throttle Not Learnt Fault

The transmission operates from default throttle calibration values which results in the evaluation of the throttle being
higher (more open) than it is. There(ore at zero throttle settings, the transmission may calculate that sufficient throttle
opening is present to justify high line pressure and switch solenoid 6 to OFF.

Other symptoms are:

a. late upshifts and

b. lock-up maintained at zero throttle when the vehicle speed is sufficiently high.

3 Engine Speed Fault

All shifts will be firm because an engine speed corresponding to peak engine torques is assumed.

If a fault is undetected, the engine speed is likely to be interpreted as stalled resulting in soft shifting possibly with an
end of shift bump.

4 Vehicle Speed Sensor Fault

All shifts will be controlled by the shift lever with skip downshifts disabled and downshifts only allowed if the

engine speed is low. Fourth gear will be inhibited.

The torque converter will be unlocked at all times.

If a fault is undetected, the vehicle is likely to be interpreted as being stationary resulting in first gear operation at all
times. Note that speedometer transducer faults are likely to cause the vehicle’s speedometer to become inoperative.

5 Gear Lever Fault (Inhibitor/PRNDL Switch)

The gear lever is assumed to be in the Drive position.

The transmission is limited to 2nd,3rd, and R gears only.

The rear band will apply at all times when the lever is shifted to P, R or N. (B2 inhibition and reverse lockout

protection is disabled.)

The torque converter will be unlocked at all times.

Manually (gear lever) initiated downshifts will not be available.

If a fault is undetected, the gear lever position is likely to be interpreted as being higher than actual. Where Park is the
highest position and Manual 1 is the lowest, the result being the availability of higher gears than selected by the gear
lever.

AUTOMATIC TRANSMISSION 5A-65

If the gear lever is incorrectly adjusted, the transmission may shift gears on bumpy road surfaces.

Transmission Oil Temperature Sensing Fault

All shifts will be firm until the transmission has warmed up, because a high transmission oil temperature is

assumed.

If a fault is undetected, the temperature is likely to be evaluated as being lower than actual, resulting in softer shifts
with ‘end bump’ (very firm feel at the end of the shift).

Mode Setting Fault

All shifts will occur as if the mode is set to ‘NORMAL’.

The mode indicator will always be off indicating that ‘NORMAL’ mode is selected.

The mode indicator will not respond to changes in switch setting.

If a fault is undetected, the mode as indicated by the mode indicator is not likely to respond to the mode switch.

Battery Voltage Sensing Fault

If the battery voltage is low then shifts to first gear are inhibited.9 the battery voltage is high (>16.5V) then the
transmission goes into limp home (LHM) mode.

If a fault is undetected, the transmission is likely to incorrectly evaluate an ON/OFF solenoid fault resulting in limp
home mode (LHM) operation.

ON/OFF Solenoid Fault (Solenoids 1,2,3 and 4)

The transmission adopts its limp home mode (LHM) operation, described above. However, if solenoid 1 is faulty then
the fourth gear LHM strategy will be adopted independent of vehicle speed.

If a fault is undetected, the operation of the transmission is dependent on which solenoid is actually faulty. The
characteristics for different solenoid fault conditions are listed in table 6.1.2.

10 ON/OFF Solenoid Fault (Solenoids 6,7)

If solenoid 6 is found faulty it is always disabled resulting in high line pressure being applied continuously.

If solenoid 7 is found faulty it is disabled resulting in the transmission being locked always.

The transmission does not go into LHM.

11 Variable Pressure Solenoid Fault

The transmission adopts its LHM operation.

If a fault is undetected, the transmission shift feel is likely to be poor for all shifts.

12 Software Fault

The transmission adopts the third gear LHM strategy of operation, independent of vehicle speed. The operation of
the TCU under this condition is difficult to predict. Its operation may be erratic.

If a fault is undetected, the operation of the TCU is likely to be erratic.

13 Power Supply Fault

The transmission adopts the third gear LHM strategy of operation, independent of vehicle speed. If there is an
intermittent power supply connection, the TCU will power-up in fourth gear and then shift to the appropriate gear to
satisfy the conditions present. The power supply is not monitored for fault evaluation.

All faults except for solenoid faults can be recovered without having to turn the TCU off and back on. However, in
general the recovery requires that no faults are present for a period of time (approx. 3 or 30 seconds). Recovery from
a fault will not clear the fault from the keep alive memory

14 Transmission Sump Temperature Exceeding 135°C

The converter lockup clutch will be applied at lower speeds, causing a shudder through the vehicle.

The mode indicator will flash in some vehicles.

These faults can be due to the transmission oil overheating or due to an incorrect signal received from the temperature
sensor.

5A-66 AUTOMATIC TRANSMISSION

Diagnostic Trouble Messages

The diagnostic trouble messages generated by the TCU and their possible causes are listed in table 6.1.3.

Table 6.1.2 - Transmission Operations for On/Off Solenoid Faults

Transmission Operation

First gear instead of second and fourth gear instead of third.

This results in a 1

4 shift as the vehicle accelerates from rest.

Second gear instead of first and third gear instead of fourth.

This results in second gear starts.

Fourth gear instead of first and third gear instead of second.

This results in fourth gear starts.

Second gear instead of third and first gear instead of fourth.

This results in a 1

2 then 2

1 (overrun) downshift as the vehicle

accelerates from rest.

The following shifts become poor:

3, 1

4, 2

1 2

3, 2

4, 4

2, 4

The following shifts become poor:

4, 4

3, 3

There may be slippage in the gears during torque converter locking.

The following shifts become poor:

2, 1

3, 1

4, 2

3, 2

4, 3

1, 3

2 (All Including Manual), 3

1,4

The following shifts become poor:

4, 3

There may be slippage in the gears during torque converter locking.

Line pressure always high.

Line pressure always low thus resulting in risk of slippage in gears.

Torque converter always unlocked.

Torque converter always locked in 3rd and 4th gears, causing the

vehicle to shudder at lower speeds,

Condition

Always ON

Always OFF

Always ON

Always OFF

Always ON

Always OFF

Always ON

Always OFF

Always ON

Always OFF

Always ON

Solenoid

Content .. 253 254 255 256 ..