Diagnosing a P1776 code on Dodge and Chrysler vehicles can be, at times, difficult. This code is set when the onboard computer thinks the Solenoid Switch Valve is latched in the Low/Reverse Position. Several things can set this code. Chrysler bulletin 21-008-04 mentions that a defective Solenoid Block can be the cause. Chrysler also mentions that a badly adjusted manual valve or defective Transmission Range Sensor can cause the code to set. A shorted Low/Reverse Pressure Switch signal wire can also cause the code to set, and of course, a stuck Solenoid Switch Valve can be the cause.
The most common problem is a worn-out Solenoid Switch Valve bore, causing TCC signal oil from the LR/CC Solenoid to enter the Low Clutch Circuit.
The LR/CC Solenoid is a dual-function solenoid used to apply the Low/Reverse clutch in first gear. As soon as the transmission shifts to 2nd gear, the LR/CC Solenoid is used to apply the torque converter clutch (partially or fully depending on the duty cycle).
Let’s use Figure 1 to see a properly functioning 42RLE. As you can see, in Park, the low clutches (Blue) are applied by the LR/CC solenoid being modulated (Green). Low clutch pressure (Blue) is at 121 Psi, the LR/CC solenoid is modulated to an average of 9.5V, and the Low-Pressure Switch (Yellow) is grounded to 0V, indicating pressure in the circuit.
When the transmission is placed in reverse, the Low/Reverse Clutches (Blue) are being applied by the manual valve through the reverse circuit side, so the LR/CC solenoid (Green) is turned off or not being Modulated (14.2V). The Low-Pressure switch (yellow) reads 14.2 V as it is not grounded, and there is no pressure on the Low clutch side of the circuit.
With the vehicle not moving and the transmission placed in neutral, the low reverse hydraulics are the same as in Park, and only the reverse clutches are released (Figure 2). When the transmission is placed in Drive, the UnderDrive clutches are applied, but the circuit we are discussing stays the same. That is, Low/Reverse clutches (Blue) are applied by the LR/CC solenoid, which is being modulated to about 9.5 average DC volts, and the Low-Pressure switch is being grounded (0V), indicating pressure in the Low Clutch Circuit. During the 1-2 shift, the LR/CC solenoid (Green) releases the Low clutches (Blue) by being modulated OFF (14.2V). The Low-Pressure switch stops being grounded (14V), indicating no pressure in the Low Clutch Circuit.
As soon as the 2-3 shift occurs (Figure 3), the TCM modulates the LR/CC solenoid (Green). At this point, the PCM can apply the TCC partially or fully. In our road test, the PCM applied the TCC in 4th gear. At this point, the LR/ CC Solenoid applies TCC fully. The low-pressure switch is not grounded, as there is no pressure in the Low/Reverse clutch circuit.
Now, let’s look at the readings when the code is set. Figure 4 is a reading taken from a stuck solenoid switch valve being detected in the circuit. As soon as the TCM starts to modulate the LR/CC solenoid (Green), pressure is present in the Low/Reverse clutch circuit (Blue), and the Low-Pressure switch (Yellow) detects the pressure. The TCM attempted to modulate the solenoid four times before it set the code and placed the transmission in fail-safe mode.
We rebuilt the transmission and installed a rebuilt valve body whose Solenoid Switch Valve circuit was reamed and tested. We were curious as to why the code was being set only after a long road test. So, we installed a pressure transducer on the Low clutch circuit and backprobed the Low-pressure switch and the LR/CC solenoid. 
All of the readings shown are from this same transmission, and it performed well until the transmission got up to about 180 degrees and under certain conditions. We wanted to make sure it was not an electrical problem. After looking at the readings from Figure 4 and seeing that the pressure rise in the Low clutch circuit coincided with the LR/CC solenoid modulation, we decided to remove the valve body. We looked closely at the switch valve and noticed a nick at the end, causing the solenoid switch valve to stick when the transmission was hot.
By monitoring the three key components: the LR/CC solenoid, Low clutch line pressure, and Low-pressure switch. It can be determined if the cause of the code is electrical, pressure leak, or stuck Switch valve. A bad range sensor can be determined by monitoring the range sensor data PID.
We hope this information will help you next time you see a P1776 code.
