AUTOMATIC TRANSMISSION SYSTEM - Pattern Select Switch Snow Mode Circuit

DESCRIPTION

Cowl side J/B ECU receives pattern select switch information, and sends it through the multiplex communication system and CAN system to the ECM.

ECT SNOW is the system that operates the throttle motor to control engine output to reduce skidding of the driving wheels, guarantee takeoff acceleration, driving straightness and turning stability.

WIRING DIAGRAM

Automatic Transmission System - Pattern Select Switch Snow Mode Circuit. A960E AUTOMATIC TRANSMISSION. Lexus IS250 IS220d GSE20 ALE20

HINT:

(*) Pattern Select Switch (ECT SNOW Switch)

When the ECT SNOW switch is pushed, the switch contact is made and the ECT SNOW mode is selected.

To cancel the ECT SNOW mode, push the ECT SNOW switch once again.

The ECT SNOW mode is automatically cancelled out when the ignition switch is turned "OFF".

INSPECTION PROCEDURE

1.DRIVING TEST

Start the engine.

Turn the ECT SNOW switch "OFF" (Normal drive mode).

Confirm vehicle response by driving from a parked position to fully depressing the accelerator pedal.

Turn the ECT SNOW switch "ON" and perform the same check as above.

Confirm that there is a difference between ECT SNOW switch "ON" and "OFF".

HINT:

Driving test should be done on a paved road (a nonskid road).

Make sure not to use the TRAC system when testing a vehicle equipped with one.

OK:
There is a difference in acceleration between "ON" and "OFF".

Go to step 2

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

2.CHECK HARNESS AND CONNECTOR (PATTERN SELECT SWITCH ASSEMBLY - BODY GROUND)

Disconnect the connector of pattern select switch.

Automatic Transmission System - Pattern Select Switch Snow Mode Circuit. A960E AUTOMATIC TRANSMISSION. Lexus IS250 IS220d GSE20 ALE20

Measure the resistance according to the value(s) in the table below.

Standard resistance:
Tester Connection Specified Condition
3 - Body ground Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.INSPECT PATTERN SELECT SWITCH ASSEMBLY

Measure the resistance according to the value(s) in the table below.

Standard resistance:
Switch Condition Tester Connection Specified Condition
Press continuously Pattern select switch
(SNOW) 1 - 3 Below 1 Ω
Release Pattern select switch
(SNOW) ↑ 10 kΩ or higher

REPLACE PATTERN SELECT SWITCH ASSEMBLY

OK

4.CHECK HARNESS AND CONNECTOR (PATTERN SELECT SWITCH ASSEMBLY - MAIN BODY ECU)

Connect the connector of pattern select switch.

Disconnect the cowl side junction block (main body ECU RH) connector.

Measure the resistance between terminal SNOW of the cowl side junction block (main body ECU RH) and body ground.

Standard resistance:
Switch Condition Tester Connection Specified Condition
Press continuously Pattern select switch
(SNOW) J75-17 (SNOW) - Body ground Below 1 Ω
Release Pattern select switch
(SNOW) ↑ 10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

Tester Connection	Specified Condition
3 - Body ground	Below 1 Ω

Switch Condition	Tester Connection	Specified Condition
Press continuously Pattern select switch (SNOW)	1 - 3	Below 1 Ω
Release Pattern select switch (SNOW)	↑	10 kΩ or higher