Lexus ES300 (1997 year). Manual - part 337

–

DIAGNOSTICS

ENGINE

DI–125

277

1997 LEXUS ES300   (RM511U)

3

Check harness and connector between ECM and stop light switch 
(See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace ECM (See page 

IN–27

).

S05470

Battery

MAIN

FL

B–G

F6

F8

1

1

1

8

14

B

Fusible

Link
Block

Engine Room J/B

2A

2J

E7

B–Y

ECM

BATT

EFI

DI–126

–

DIAGNOSTICS

ENGINE

278

1997 LEXUS ES300   (RM511U)

DTC

P1600

ECM BATT Malfunction

CIRCUIT DESCRIPTION

Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for
use by the DTC memory and air–fuel ratio adaptive control value memory, etc.

DTC No.

DTC Detecting Condition

Trouble Area

P1600

Open in back up power source circuit

Open  in  back up power source circuit

ECM

HINT:If DTC P1600 appear, the ECM does not store another DTC. 

WIRING DIAGRAM

DI0A5–01

A00241

LOCK

BATT(+)

BE6653
P24330

S04162

Engine Room J/B

EFI Fuse

–

DIAGNOSTICS

ENGINE

DI–127

279

1997 LEXUS ES300   (RM511U)

INSPECTION PROCEDURE

1

Check voltage between terminal BATT of ECM connector and body ground.

PREPARATION:
Remove the glove compartment (See page 

SF–64

).

CHECK:
Measure voltage between terminal BATT of ECM connector
and body ground.
OK:

Voltage:  9 

∼ 

14 V

OK

 Check and replace ECM (See page 

IN–27

).

NG

2

Check EFI fuse.

PREPARATION:
Remove the EFI fuse from the engine room J/B.
CHECK:
Check continuity of EFI fuse.
OK:

Continuity

NG

 Check for short in all harness and components
 connected to EFI fuse.

OK

Check and repair harness or connector
between battery, EFI fuse and ECM.

DI–128

–

DIAGNOSTICS

ENGINE

280

1997 LEXUS ES300   (RM511U)

DTC

P1780

Park/Neutral Position Switch Malfunction

CIRCUIT DESCRIPTION

The park/neutral position switch go on when the shift lever is in the N or P shift position. When it goes on
terminal NSW of the ECM is grounded to body ground via the starter relay, thus the terminal NSW voltage
becomes 0V. When the shift lever is in the D, 2, L or R position, the park/neutral position switch goes off,
so the voltage of ECM. Terminal NSW becomes battery voltage, the voltage of the ECM internal power
source. If the shift lever is moved from the N position to the D position, this signal is used for air–fuel ratio
correction and for idle speed control (estimated control), etc. 
 

DTC No.

DTC Detecting Condition

Trouble Area

2 or more switches are ON simultaneously for ”N”, ”2”,

 

”L” and

”R” positions

 (2 trip detection logic)

Sh t i

k/

t l

iti

it h i

it

P1780

When driving under conditions (a) and (b) for 30 sec. or more

the park/neutral position switch is ON (N position):

(2 trip detection logic)

(a) Vehicle speed:  70 km/h (44 mph) or more

(b) Engine speed:  1,500 

∼

 2,500 rpm

Short in park/neutral position switch circuit

Park/neutral position switch

ECM

HINT:After confirming DTC P1780 use the LEXUS hand–held tester to confirm the PNP switch signal from
”CURRENT DATA”.

DI0A6–01