Lexus ES300 (1997 year). Manual — part 348

Q07781

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–169

321

1997 LEXUS ES300 (RM511U)

DTC

P0750, P0755

Shift Solenoid A/B Malfunction
(Shift Solenoid Valve No.1/No.2)

SYSTEM DESCRIPTION

The ECM uses signals from the vehicle speed sensor to detect the actual gear position (1st, 2nd, 3rd or O/D
gear).
Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical
trouble of the shift solenoid valves and valve body.

DTC No.

DTC Detecting Condition

Trouble Area

P0750

P0755

During normal driving, the gear required by the ECM does not

match the actual gear

(2 trip detection logic)

Shift solenoid valve No.1/No.2 is stuck open or closed

Valve body is blocked up or stuck

Check the shift solenoid valve No.1 when DTC P0750 is output and check the shift solenoid valve No.2 when
DTC P0755 is output.

INSPECTION PROCEDURE

1

Check shift solenoid valve No.1 or No.2 operation.

PREPARATION:
(a)

Remove the oil pan.

(b)

Remove the shift solenoid valve No.1 or No.2.

CHECK:
(a)

Applying 490 kPa (5 kgf/cm

2

, 71 psi) of compressed air,

check that the solenoid valve does not leak air.

(b)

When battery positive voltage is supplied to the shift sole-
noid valve, check that the valve opens.

NG

Replace the shift solenoid valve No.1 or No.2.

OK

Check the valve body (See page

DI–164

).

DI0CS–01

Position

NORMAL

SHIFT SOLENOID NO.1
MALFUNCTIONING

Solenoid valve
No.1

No.2

Gear

SHIFT SOLENOID NO.2
MALFUNCTIONING

BOTH SOLENOIDS MAL-
FUNCTIONING

Solenoid valve
No.1

No.2

Gear

Solenoid valve
No.1

No.2

Gear

Gear when shift selector is
manually operated

D

2

L

ON

ON

OFF

ON

ON

OFF

OFF

OFF

ON

ON

OFF

ON

ON

OFF

ON

ON

ON

OFF

1st

2nd

3rd

O/D

1st

2nd

3rd

1st

2nd

X

X

X

X

X

X

X

X

X

ON

ON

OFF

OFF

ON

ON

ON

3rd

3rd

O/D

3rd

3rd

1st

2nd

X

X

X

X

X

X

X

X

X

OFF

OFF

ON

ON

OFF

OFF

OFF

ON

ON

1st

O/D

O/D

1st

O/D

O/D

O/D

1st

1st

O/D

O/D

O/D

O/D

O/D

O/D

O/D

1st

1st

X: Malfunctions

ON

ON

3rd

3rd

DI–170

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

322

1997 LEXUS ES300 (RM511U)

DTC

P0753, P0758

Shift Solenoid A/B Electrical Malfunc-
tion (Shift Solenoid Valve No.1/No.2)

CIRCUIT DESCRIPTION

Shifting from 1st to O/D is performed in combination with ON and OFF of the shift solenoid valves No.1 and
No.2 controlled by ECM. If an open or short circuit occurs in either of the shift solenoid valves, the ECM con-
trols the remaining normal shift solenoid valve to allow the vehicle to be operated smoothly (Fail safe func-
tion).
Fail Safe Function:
If either of the shift solenoid valve circuits develops an open or short, the ECM turns the other shift solenoid
ON and OFF to shift to the gear positions shown in the table below. The ECM also turns the shift solenoid
valve SL OFF at the same time. If both solenoids are malfunction, hydraulic control cannot be performed
electronically and must be done manually.
Manual shifting as shown in the following table must be done (In the case of a short circuit, the ECM stops
sending current to the short circuited solenoid).

Check the shift solenoid valve No.1 when DTC P0753 is output and check the shift solenoid valve No.2 when
DTC P0758 is output.

DTC No.

DTC Detecting Condition

Trouble Area

P0753

P0758

The ECM checks for an open or short circuit in the shift sole-

noid valves No.1 and No.2 circuit when it changes.

The ECM records DTC P0753 or P0758 if condition (a) or (b) is

detected once, but it does not light up MIL.

After ECM detects condition a) or b) continuously 8 times or

more in a trip and the MIL light up.

(a) When the solenoid is energized, the solenoid resistance

is 8

Ω

or less and is counted.

(b) When the solenoid is not energized, the solenoid resis

tance is 100 k

Ω

or more and is counted.

Open or short in shift solenoid valve No.1/No.2 circuit

Shift solenoid valve No.1/No.2

ECM

DI0CT–01

D00033

Transaxle

Shift Solenoid
Valve No.1

Shift Solenoid
Valve No.2

3

6

E3

E3

V

L–B

L–B

J/C
J26

A

A

A

Cruise Control ECU

17

11

B+

S1

S2

B+

ECM

E10

E10

Q07642

S1

S2

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

DI–171

323

1997 LEXUS ES300 (RM511U)

WIRING DIAGRAM

INSPECTION PROCEDURE

1

Measure resistance between terminal S1 or S2 of ECM and body ground.

PREPARATION:
Disconnect the connector from ECM.
CHECK:
Measure resistance between terminal S1 or S2 of ECM and
body ground.
OK:

Resistance: 11

∼

15

Ω

OK

Check and replace the ECM.

NG

D00047

S1

S2

S1

S2

DI–172

–

DIAGNOSTICS

AUTOMATIC TRANSAXLE

324

1997 LEXUS ES300 (RM511U)

2

Check harness and connector between ECM and automatic transaxle solenoid
connector.

PREPARATION:
Disconnect the solenoid connector from the automatic trans-
axle.
CHECK:
Check the harness and connector between terminal S1 or S2
of ECM and terminal S1 or S2 of solenoid connector.
OK:

There is no open and no short circuit.

NG

Repair or replace the harness or connector.

OK