AUTOMATIC TRANSMISSION ± Troubleshooting <A/T>
23-21
INSPECTION PROCEDURE 8
Upshifting occurs spontaneously
Probable cause
Upshifting occurs in ranges where upshifting should not occur, e. g. upshifting to
2nd gear in L range, 3rd gear in 2 range or 4th gear in D range when overdrive
is disconnected.
D Malfunction of inhibitor switch
D Malfunction of overdrive switch
D Malfunction of A/T-ECU
MUT-II SERVICE DATA
D 37 ± Inhibitor switch
OK: MUT-II display and selector
lever position should match
NG
Inspection Procedure 14 ± Inhibitor
switch system (Refer to P. 23-25.)
OK
MUT-II SERVICE DATA
D 35 ± Overdrive switch
OK: MUT-II display and mode
selected should match
NG
Inspection Procedure 15 ± Overdrive
switch system (Refer to P. 23-25.)
OK
Replace the A/T-ECU.
INSPECTION PROCEDURE 9
Incorrect drive gear position
Probable cause
Vehicle starts off in 2nd, 3rd or 4th gear when in D range. Often occurs when starting
off is not smooth.
D Malfunction of inhibitor switch
D Malfunction of direct clutch
D Malfunction of planetary gear
D Malfunction of valve body
D Malfunction of forward clutch
D Malfunction of solenoid valve No. 1
D Malfunction of A/T-ECU
L: Refer to the Transmission Workshop Manual.
MUT-II SERVICE DATA
D 37 ± Inhibitor switch
OK: MUT-II display and selector
lever position should match
NG
Inspection Procedure 14 ± Inhibitor
switch system (Refer to P. 23-25.)
OK
Does the vehicle move forward in 2nd
gear?
Yes
Inspection Procedure 6 ± Downshifting
does not occur (Refer to P. 23-20.)
No
Does the vehicle move forward in 3rd
gear? (D range)
Yes
Does the vehicle reverse in R range?
Yes
Check the direct clutch. L
No
No
Check the planetary gear. L
Does the vehicle move forward in 3rd
gear? (2, L range)
Yes
Malfunction of 2±3 shift valve L
Malfunction of solenoid valve No. 1L
No
Does the vehicle move forward in 4th
gear?
Yes
Does the vehicle reverse in R range?
Yes
Malfunction of solenoid valve No.
1 L
No
No
Check the forward clutch. L
Malfunction of 2±3 shift valve L
Check the trouble symptoms.
NG
Replace the A/T-ECU.
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