E057

TEST CONDITIONS
1. Code EO24 not set;
2. Transmission in drive or reverse;
3. ECM is commanding fourth gear;
4. Vehicle speed equal to or greater than 0;
5. 3rd gear discrete present (3rd gear switch open).

FAILURE CONDITIONS
Fourth gear input to ECM grounded (no fourth gear) for 6 seconds.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. Viscous converter clutch is disabled.

DESCRIPTION
The fourth gear switch is normally closed (grounded) switch located in the transmission that opens when 4th gear hydraulic oil is applied to it. CKT 446 is grounded when the 4th gear switch is closed and has 12 volts on it when the 4th gear switch is open.

Code EO57 will set if the ECM commands 4th gear and the switch stays closed or if the transmission does not shift to 4th gear. Code EO57 will set if either the 4th gear switch is faulty or if the 3-4 shift solenoid is faulty.

Notes on Fault Tree
1. Checking for 4th gear operation and gear status. °F will light if CKT 108 and 446 are open (3rd and 4th gear) and °C will light if only CKT 108 is open (3rd gear).
2. Checking for open 3-4 shift solenoid.
3. Checking for a short in CKT 446.

Notes on Intermittents
Drive the vehicle in D3 while observing gear status lights °C and °F. Shift to D4 and watch for °F. If the transmission shifts and °C stays on, check for a sticking or shorted to ground 4th gear switch. If the transmission does not shift, check the operation of the 3-4 shift solenoid. See Transmission and Drivetrain for transmission diagnosis. Testing and Inspection