E056

TEST CONDITIONS
1. Code EO24 not set;
2. Transmission in drive or reverse;
3. ECM is not commands fourth gear;
4. Engine is running.

FAILURE CONDITIONS
Fourth gear input to ECM open (fourth gear present) 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 a normally closed (grounded) switch located in the transmission that opens when 4th gear hydraulic oil is applied to it CKT 446 will be grounded when the 4th gear switch is closed and has 12 volts on it when the 4th gear switch is open.

Code EO56 will set if the ECM is not commanding 4th gear but the fourth gear switch is open. Code EO56 will set if either the 4th gear switch circuit is open or if the 3-4 shift solenoid is shorted to ground causing it to shift to 4th gear all the time.

Notes on Fault Tree
1. Checking for transmission gear status at idle. °C will light if CKT 438 is open (3rd gear), °F will light if CKT 438 and 446 are open (3rd and 4th gear), and °E will light if CKT 446 is open and 438 is grounded (4th without 3rd gear).
2. Checking for an open in 4th gear switch circuit.
3. Checking for a open in CKT 446.
4. Checking for an improperly functioning 3-4 shift solenoid. In D3, the transmission should not shift to fourth gear. If it does, check for a short to ground in CKT 898.
5. Checking for the ECM's ability to cycle the 3-4 shift solenoid. Voltage should cycle from 12 volts to 0 volts every 3 seconds.
6. Checking for a low resistance 3-4 shift solenoid. Solenoid should be 'above 20 ohms.

Notes on Intermittents
At key "ON", engine "OFF", manipulate transmission connector, transmission wiring, and ECM connector while observing the fourth gear status light (°F). if the fourth gear status indicator flashes on, repair intermittent open in CKT 446 (fourth gear).