Lexus ES300 (1997 year). Manual - part 431

N16045

3

4

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–501

653

1997 LEXUS ES300   (RM511U)

3

Check control switch.

PREPARATION:
(a)

Remove steering wheel center pad.

(b)

Disconnect the control switch connector.

CHECK:
Measure resistance between terminals 3 and 4 of control switch
connector when control switch is operated.

Switch position

Resistance (

Ω

)

Neutral

∞

 (No continuity)

RES/ACC

50 – 80

SET/COAST

180 – 220

CANCEL

400 – 440

NG

Replace control switch.

OK

4

Check harness and connector between cruise control ECU and cruise control switch,
cruise control switch and body ground (See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

5

Input signal check (See step 1).

OK

Wait and see.

NG

Check and replace cruise control ECU 
(See page 

IN–27

).

N21220

Cruise Control ECU

IDL

13

L–R

ECM

IDLO

E7

11

C14

DI–502

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

654

1997 LEXUS ES300   (RM511U)

DTC

    51

Idle Signal Circuit

CIRCUIT DESCRIPTION

When the idle switch in turned ON, a signal is sent to the ECU. The ECU uses this signal to correct the dis-
crepancy between the throttle valve position and the actuator position sensor value to enable accurate
cruise control at the set speed. If the idle switch is malfunctioning, problem symptoms also occur in the en-
gine, so also inspect the engine.

DTC No.

Detection Item

Trouble Area

51

Short in idle signal circuit.

Harness or connector between ECM and throttle position

sensor

Throttle position sensor

Harness or connector between cruise control ECU and ECM

Cruise control ECU

WIRING DIAGRAM

DI0EW–01

AB0119
N19913

I00740

ON

IDL

(–)

(+)

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

DI–503

655

1997 LEXUS ES300   (RM511U)

INSPECTION PROCEDURE

1

Check voltage between terminal IDL of cruise control ECU connector and body
ground.

PREPARATION:
(a)

Remove the ECU with connector still connected.

(b)

Disconnect the ECM connector.

(c)

Turn ignition switch ON.

CHECK:
Measure voltage between terminal IDL of ECU connector and
body ground when the throttle valve is fully closed and fully
opened.
OK:

Throttle valve position

Voltage

Fully opened

10 – 14 V

Fully closed

Below 2 V

OK

Proceed to next circuit inspection shown on
problem symptom table (See page 

DI–487

).

NG

2

Check harness and connector between ECM and throttle position sensor 
(See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

3

Check throttle position sensor circuit (See page 

DI–38

).

NG

Replace throttle position sensor.

OK

N22085

1

2

3

DI–504

–

DIAGNOSTICS

CRUISE CONTROL SYSTEM

656

1997 LEXUS ES300   (RM511U)

4

Check throttle position sensor.

PREPARATION:
Disconnect the throttle position sensor connector.
CHECK:
Measure resistance between terminals 1, 3 and 2 of throttle
position sensor connector.
OK:

Terminals

Throttle valve position

Resistance

1 – 2

–

2.5 

∼

 5.9 k

Ω

2 – 3

Fully opened

0.2 

∼

 6.3 k

Ω

2 – 3

Fully closed

2.0 

∼

 10.2 k

Ω

NG

Replace throttle position sensor.

OK

5

Check for open and short in harness and connector between cruise control ECU
and ECM (See page 

IN–27

).

NG

Repair or replace harness or connector.

OK

Check and replace cruise control ECU 
(See page 

IN–27

).