Solenoid Valve BackUp Function

In the event that the shift solenoids malfunction, the ECU can still control the transmission by operating the remaining solenoid to put the transmission in a gear that will allow the vehicle to continue to run.

The chart below identifies the gear position the ECU places the transmission if a given solenoid should fail. Notice that if the ECU was not equipped with fail-safe, the items in parenthesis would be the normal operation. But because the ECU senses the failure, it modifies the shift pattern so the driver can still drive the vehicle. For example, if No. 1 solenoid failed, the transmission would normally go to overdrive in drive range first gear. But instead, No. 2 solenoid turned it on to give 3rd gear.

Solenoid Valve Back-Up Function Chart

RANGE

NORMAL

NO. 1 SOLENOID MALFUNCTIONING

NO. 2 SOLENOID j BOTH SOLENOIDS MALFUNCTIONING MALFUNCTIONING

Solenoid valve

Gear

Solenoid valve

Gear

Solenoid valve

Gear

Gear when shift lever is manually operated

NO. 1 1 NO. 2

NO. 1 | NO. 2

NO. 1 1 NO. 2

"D"

ON

OFF

1st

x I 0N x : (OFF)

3rd (O/D)

ON

x 1 1st

O/D

ON I ON

2nd

X

ON

3rd

(ON)

X

O/D (1st)

O/D

OFF

ON

3rd

x I ON

3rd

OFF 1 x 1 O/D

O/D

OFF

OFF

O/D

x , OFF

O/D

OFF 1 x ! O/D

O/D

"2"

ON

OFF

1st

X

ON (OFF)

3rd (O/D)

ON

X

1st I 3rd*

ON

ON

2nd

X

ON

3rd

(ON)

X

3rd* (1st)

3rd*

OFF

ON

3rd

X

ON

3rd

OFF

X

3rd*

3rd*

"L"

ON

OFF

1st

X

OFF

1st

ON

X

1st

1st

ON

ON

2nd

X

ON

2nd

ON x j 1st

1st

( ): If no fail-safe function were provided x: Malfunctions

*0/D in the A540E, A540H

( ): If no fail-safe function were provided x: Malfunctions

*0/D in the A540E, A540H

Should both solenoids malfunction, the driver can still safely drive the vehicle by operating the shift lever manually.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

Get My Free Ebook


Post a comment