Hi. This one of the most misdiagnosed problems we see. Trace your wiring and check the pcm connectors for any obvious problems. I will send you the diagnostic tree for this, but it requires a special tool/tester. The MOST common problem is the valvebody. What is called the solenoid switch valve sticks and binds, and the valve body needs replaced.
Here is that diagnostic chart:
P1776-SOLENOID SWITCH VALVE LATCHED IN LR POSITION
When Monitored and Set Condition:
When Monitored: Continuously when performing partial or full EMCC - PEMCC or
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.
RELATED DTC P0841 PRESENT
LR PRESSURE SWITCH SENSE CIRCUIT OPEN
LR PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
SOLENOID SWITCH VALVE
POWERTRAIN CONTROL MODULE
INTERMITTENT WIRING AND CONNECTORS
TEST ACTION APPLICABILITY
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
With the DRBIIIt, read the engine DTC's. Check and repair all Engine DTC's prior
to performing Transmission symptom diagnostics.
With the DRBIIIt, read Transmission DTC's. Record all DTC's and 1 Trip Failures.
NOTE: Diagnose 1 Trip Failures as a fully matured DTC.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Perform the Shift Lever Position Test. If the test does not pass, refer to Symptom test
for P0706 Check Shifter Signal.
For Gear Ratio DTC's, check and record all CVI's.
Most DTC's set on start up but some must be set by driving the vehicle to ensure that
all diagnostic monitors have run.
NOTE: Verify flash level of Powertrain Controller. Some problems are
corrected by software upgrades to the Transmission and Engine Systems.
NOTE: Due to the integration of the Powertrain and Transmission control
modules - if a controller flash is performed it is necessary to perform Quick
Learn and the Drive Learn procedures. Failure to do so may result in shift
NOTE: Check for applicable TSB's that may apply.
Perform this procedure prior to Symptom diagnosis.
Go To 2
2 With the DRBIIIt, check for other transmission DTC's
Is the DTC P0841 present also?
Yes ! Refer to the Transmission category and perform the appropriate
Perform (NGC) 45RFE/545RFE TRANSMISSION VERIFICATION
TEST - VER 1.
No ! Go To 3
3 With the DRBIIIt, Check the STARTS SINCE SET counter.
NOTE: This counter only applies to the last DTC set.
Is the STARTS SINCE SET counter 2 or less?
Yes ! Go To 4
No ! Go To 9
4 Turn the ignition off to the lock position.
Remove the Starter Relay.
NOTE: Removal of the Starter Relay is to prevent a Transmission, NO
RESPONSE, condition and disable the starter.
Install Transmission Simulator, Miller tool #8333.
Note: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector switch to the LR
With the DRBIIIt, monitor the LR Pressure Switch state while pressing the Pressure
Switch Test button on the Transmission Simulator.
Did the state of the LR Pressure Switch change while pressing the Pressure Switch
Yes ! Go To 5
No ! Go To 6
5 Remove the Valve Body per the Service Information.
Inspect the Solenoid Switch Valve for sticking in the bore and/or wear.
Were there any problems found?
Yes ! Clean and repair as necessary per the Service Information.
6 Turn the ignition off to the lock position.
Disconnect the PCM C4 harness connector.
Disconnect the Transmission Solenoid /TRS Assembly harness connector
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 SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
Measure the resistance of the LR Pressure Switch Sense circuit from the appropriate
terminal of special tool #8815 to the Solenoid/TRS Assembly harness connector.
Is the resistance above 5.0 ohms?
Yes ! Repair the LR Pressure Switch Sense circuit for an open.
No ! Go To 7
7 Turn the ignition off to the lock position.
Disconnect the Transmission Solenoid/TRS Assembly harness connector.
Measure the resistance between ground and the LR Pressure Switch Sense circuit.
Is the resistance below 5.0 ohms?
Yes ! Repair the LR Pressure Switch Sense circuit for a short to ground.
No ! Go To 8
8 Using the schematics as a guide, inspect the wiring and connectors. Repair as
necessary. Pay particular attention to all power and ground circuits.
If there are no possible causes remaining, view repair.
Replace the Powertrain Control Module per the Service Information.
WITH THE DRBIIIt PERFORM QUICK LEARN
9 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
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 a worn Solenoid Switch Valve or plugs.
With the DRBIIIt, check the EATX DTC EVENT DATA to help identify the
conditions in which the DTC was set.
Yes ! Repair as necessary.
No ! Test Complete.