68RFE Automatic Transmission

P1776-SOLENOID SWITCH VALVE LATCHED IN LR POSITION





For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams


Theory of Operation


The Solenoid Switch Valve (SSV) controls the direction of the transmission fluid when the L/R Solenoid is energized. The SSV will be in the downshifted position in 1st gear, thus directing the fluid to the L/R clutch circuit. In 2nd through 6th gears, it will be in the upshifted position and directing the fluid into the torque converter clutch (TCC) control circuit.


When in 2nd through 6th gear, the Torque Converter Clutch (TCC) can be engaged when certain conditions are met. The TCC piston is electronically modulated by increasing the duty cycle of the L/R solenoid until the torque converter slip difference (difference between engine and transmission input speed) is within 60 rpm. Then the L/R solenoid is fully energized (FEMCC - 100% duty cycle). Torque converter slip is monitored in FEMCC to ensure adequate clutch capacity.


- When Monitored:

Continuously when performing partial or full EMCC - PEMCC or FEMCC.

- Set Condition:

If the transmission senses the L/R pressure switch closing while performing PEMCC or FEMCC. This DTC will set after two unsuccessful attempts to perform PEMCC or FEMCC. This DTC can take up to five minutes of problem identification before illuminating the MIL.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 68RFE Pre-Diagnostic Troubleshooting Procedure



Diagnostic Test


1. CHECK FOR RELATED DTCS

With the scan tool, check for other transmission DTCs.

Is the DTC P0841 present also?

Yes

- Refer to the Transmission category and perform the appropriate symptom.

No

- Go To 2



2. CHECK TO SEE IF DTC P1776 IS CURRENT

With the scan tool, Check the STARTS SINCE SET counter.


NOTE: NOTE: This counter only applies to the last DTC set.

Is the STARTS SINCE SET counter 2 or less?

Yes

- Go To 3

No

- Go To 7



3. CHECK THE PCM AND WIRING

Turn the ignition off to the lock position.

Remove the Ignition Switch Feed fuse from the TIPM.


CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.


WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.

Install the Transmission Simulator, Miller tool #8333.

Ignition on, engine not running.

With the Transmission Simulator, turn the Pressure Switch selector switch to the L/R position.

With the scan tool, monitor the L/R Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.

Did the state of the L/R Pressure Switch change while pressing the Pressure Switch Test button?

Yes

- Go To 4

No

- Go To 5



4. CHECK THE SOLENOID SWITCH VALVE

Remove the Valve Body.

Inspect the Solenoid Switch Valve and plugs for sticking in the bore and/or wear.

Were there any problems found?

Yes

- Clean and repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test

No

- Go To 7



5. CHECK THE L/R PRESSURE SIGNAL CIRCUIT FOR AN OPEN





Turn the ignition off to the lock position.

Disconnect the Transmission Simulator, Miller tool #8333.

Disconnect the PCM C4 harness connector and connect Miller tool #8815.


CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.

Measure the resistance of the (T50) L/R Pressure Signal circuit between the Solenoid/TRS Assembly harness connector and the appropriate terminal of Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

- Repair the (T50) L/R Pressure Signal circuit for an open.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test

No

- Go To 6



6. CHECK THE (T50) L/R PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND





Measure the resistance between ground and the (T50) L/R Pressure Signal circuit.

Is the resistance below 5.0 ohms?

Yes

- Repair the (T50) L/R Pressure Signal circuit for a short to ground.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test

No

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the PCM. With the scan tool, perform QUICK LEARN.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test


7. CHECK WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.

Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.

Wiggle the wires while checking for shorted and open circuits.

This DTC can also be set by the Solenoid Switch Valve intermittently sticking in it's bore under extreme temperature conditions, or by a worn Solenoid Switch Valve or plugs.

With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Where there any problems found?

Yes

- Repair as necessary.
- Perform 68RFE TRANSMISSION VERIFICATION TEST. 68RFE Transmission Verification Test

No

- Test Complete.