Chrysler introduced a Variable Line Pressure Solenoid to the existing 41TE (A604) and 42RLE transmission as early as 2007. The addition of this solenoid includes the use of a transducer to verify line pressure control as feed back to the computer. 41TES and 42RLE-VLP are the new designations for the units equipped with the added solenoid and transducer.
This is what the added line pressure control solenoid does, it lowers line pressure when it duty cycles. Characteristically, line pressure solenoids are normally applied solenoids controlling line pressure on the spring side of the pressure regulator valve. The regulated pressure this type of solenoid generally produces runs from 0 psi at 1 amp to 90 psi at 0.1 amps. The added pressure to the spring side of the pressure regulator valve is what raises line pressure. The design of the solenoid is that should it turn off, maximum line pressure will result as a failsafe strategy.
The 41TES/42RLE-VLP line pressure solenoid works entirely different. This is a normally vented solenoid. The regulated pressure this solenoid produces generally runs from 90 psi at 1 amp to 0 psi at 0.1 amps. This regulated pressure works the end of the pressure regulator valve opposite the spring. As it is energized it lowers pressure. As it turns off it restores pressure back to predetermined levels (higher pressure).
The operation of the solenoid is important to understand when it comes to diagnosing problems related to the solenoid and/or transducer.
There are six main codes assigned to this system. They are:
P0868: Line pressure low
P0869: Line pressure high
P0932: Line pressure sensor circuit
P0934: Line pressure sensor circuit low
P0945: Line pressure sensor circuit high
P1745: Transmission line pressure too high for too long
The following is detailed O. E. diagnostic information for each of these codes:
The PCM continuously monitors Actual Line Pressure (the transducer signal-LPS) and compares it to Desired Line Pressure (VLPS command). If the Actual Line Pressure is more than 10 psi below Desired Line Pressure, this DTC will set.
Possible Causes (no specific order):
Check for related DTC’s
Low Fluid Level
Transducer (LPS) 5 volts supply circuit open
Transducer (LPS) 5 volts supply circuit shorted to ground
Transducer (LPS) 5 volts supply circuit short to voltage
VLPS control circuit shorted to another circuit
Internal transmission failure
Malfunctioning Transducer (LPS)
Malfunctioning VLPS
Cracked, plugged, or mis-installed Primary Oil Filter
Stuck or Sticking Pressure Regulator Valve
Malfunctioning PCM
Theory of Operation
Line pressure is monitored by the Transducer and regulation is achieved by changing the duty cycle of the VLPS controlled by the Transmission Control System in the PCM. 5% duty cycle = solenoid OFF which equals maximum line pressure. 62% duty cycle = solenoid ON which equals minimum line pressure. The Transmission Control System calculates the desired line pressure based on inputs from both engine load and transmission.
The Transmission Control System calculates torque input to the transmission and uses it as the primary input to the desired pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 or 931 kPa (120 or 135 psi) during shifts and in Park and Neutral to ensure consistent shift quality. The desired line pressure is continuously being compared to the actual line pressure. If the actual line pressure is consistently lower than the target while driving, the line pressure low DTC P0868 will set.
Code P0869 - Line Pressure High
The PCM continuously monitors Actual Line Pressure (the transducer signal). If the Actual Line Pressure reading is greater than the highest Desired Line Pressure (VLPS command) ever used in the current gear, while the VLPS duty cycle is at or near maximum value (which should result in minimum line pressure), this DTC will set.
Possible Causes (no specific order):
Transducer (LPS) 5 volts supply circuit open
Transducer (LPS) 5 volts supply circuit shorted to ground
Transducer (LPS) ground circuit open
Transducer (LPS) connection faulty
Malfunctioning Transducer (LPS)
VLPS control circuit open
Transmission Control Relay Output Circuit Open
Mechanical failure of the VLPS
Stuck or Sticking Pressure Regulator Valve
Malfunctioning PCM
Theory of Operation
Line pressure is measured by the Transducer and regulation is achieved by changing the duty cycle of the VLPS controlled by the Transmission Control System in the PCM. 5% duty cycle = solenoid OFF which equals Maximum line pressure. 62% duty cycle = solenoid ON which equals minimum line pressure. The Transmission Control System calculates the desired line pressure based on inputs from both engine load and transmission.
The Transmission Control System calculates torque input to the transmission and uses it as the primary input to the desired pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 or 931 kPa (120 or 135 psi) during shifts and in Park and Neutral to ensure consistent shift quality. The desired line pressure is continuously being compared to the actual line pressure. If the actual line pressure is consistently higher than the highest desired line pressure ever used in the current gear, the line pressure high DTC P0869 will set.
Possible Causes (no specific order):
Check for related DTC’s
Faulty VLPS connector and wiring
Internal transmission failure
Malfunctioning PCM
Theory of Operation
Line pressure is electronically controlled by the Transmission Control System and is measured by the Transducer (Line Pressure Sensor - LPS). The desired line pressure is continuously being compared to the Actual Line Pressure and is regulated electronically changing the duty cycle of the VLPS. 5% duty cycle = solenoid OFF which equals maximum line pressure. 62% duty cycle = solenoid ON which equals minimum line pressure.
The Transmission Control System calculates the desired pressure based on inputs from the transmission and engine. A calculated torque input to the transmission is used as the primary input of the desired line pressure calculation and is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 to 931 kPa (120 to 135 psi) during shifts and in Park and Neutral to ensure shift quality.
Code P0934 - Line Pressure Sensor Circuit Low
The DTC will set when the monitored Transducer (Line Pressure Sensor - LPS) signal voltage is less than or equal to 0.35 volts for 0.18 seconds.
Possible Causes (no specific order):
Transducer (LPS) 5 volts supply circuit open
Transducer (LPS) 5 volts supply circuit shorted to ground
Transducer (LPS) signal circuit shorted to ground.
Malfunctioning Transducer (LPS)
Malfunctioning PCM
Theory of Operation
Line pressure is electronically controlled by the Transmission Control System and is measured by the Transducer (Line Pressure Sensor - LPS). The desired line pressure is continuously being compared to the Actual Line Pressure and is regulated electronically changing the duty cycle of the VLPS. 5% duty cycle = solenoid OFF which equals maximum line pressure. 62% duty cycle = solenoid ON which equals minimum line pressure.
The Transmission Control System calculates the desired pressure based on inputs from the transmission and engine. A calculated torque input to the transmission is used as the primary input of the desired line pressure calculation and is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 to 931 kPa (120 to 135 psi) during shifts and in Park and Neutral to ensure shift quality.
The monitored Transducer (LPS) signal voltage should always be between 0.35 and 4.75 volts. Any monitored voltages outside of these parameters indicate a faulty Transducer or associated wiring and will cause either DTC P0934 or P0935 to set.
Code P0935 - Line Pressure Sensor Circuit High
The DTC will set when the monitored Transducer (Line Pressure Sensor - LPS) signal voltage is greater than or equal to 4.75 volts for the period of 0.18 seconds.
Possible Causes (no specific order):
Transducer (LPS) sensor ground circuit open
Transducer (LPS) signal circuit shorted to power
Malfunctioning Transducer (LPS)
Malfunctioning PCM
Theory of Operation
Line pressure is electronically controlled by the Transmission Control System and is measured by the Transducer (Line Pressure Sensor - LPS). The desired line pressure is continuously being compared to the Actual Line Pressure and is regulated electronically changing the duty cycle of the VLPS. 5% duty cycle = solenoid OFF which equals maximum line pressure. 62% duty cycle = solenoid ON which equals minimum line pressure.
The Transmission Control System calculates the desired pressure based on inputs from the transmission and engine. A calculated torque input to the transmission is used as the primary input of the desired line pressure calculation and is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 to 931 kPa (120 to 135 psi) during shifts and in Park and Neutral to ensure shift quality.
The monitored Transducer (LPS) signal voltage should always be between 0.35 and 4.75 volts. Any monitored voltages outside of these parameters indicate a faulty Transducer or associated wiring and will cause either DTC P0934 or P0935 to set.
Code P1745 - transmission line pressure too high for too long
Set Condition: If the transmission has been operating in an open-loop line pressure control for 3220 kilometers (2000 miles) or 1000 2-3 upshifts.
When Monitored: Continuously with ignition on.
Possible Causes (no specific order):
Mechanical failure of the VLPS
Stuck or Sticking Pressure Regulator Valve
Transducer (LPS) sensor ground circuit open
Transducer (LPS) signal circuit shorted to power
Malfunctioning Transducer (LPS)
Theory of Operation
This DTC is an informational DTC to inform the technician that transmission has been operating in an open-loop line pressure control for 3220 kilometers (2000 miles) or 1000 2-3 upshifts resulting from a Line Pressure DTC. The 42RLE Transmission is not designed to operate in open-loop line pressure control for an extended period time. This DTC is intended to protect the transmission. If the DTC sets, the transmission controller will place the transmission into limp-in mode.
NOTE: In order to erase this DTC you must reset (erase) the VLP Shift Counter and the Output tooth counter. This is a single procedure in the scan tool called "Clear Variable Line Pressure (VLP) counters". If you do not erase this code the vehicle will remain in failsafe regardless of completing all necessary repairs.
