P1735 indicates a shift solenoid performance problem in your 2010 Chrysler Pacifica's automatic transmission. Shift solenoids are electromechanical valves that control fluid flow to specific clutch packs, enabling gear changes based on TCM commands. When a solenoid fails to operate as commanded, shift quality suffers and diagnostic codes set.
Automatic transmissions use various types of solenoids for different functions. Shift solenoids direct fluid to clutch circuits to engage specific gears. Pressure control solenoids regulate line pressure based on load, speed, and shift phase. The torque converter clutch solenoid controls lockup engagement for improved efficiency.
When a solenoid sticks or fails to respond properly, the transmission may experience harsh shifts, delayed engagement, failure to shift into certain gears, or complete gear inhibit. The TCM monitors solenoid circuit resistance and operation time to detect faults—if a solenoid takes too long to respond or draws incorrect current, P1735 sets.
Solenoid Testing Procedures
Disable the transmission by disconnecting the negative battery cable before accessing the transmission internal wiring. Locate the affected solenoid at the valve body and test resistance with a multimeter. Typical shift solenoid resistance ranges from 10-25 ohms depending on the manufacturer. Compare readings against factory specifications and test adjacent solenoids for comparison.
Check for internal shorts by measuring resistance between the solenoid terminal and case ground. Continuity indicates damaged windings requiring solenoid replacement. Also check for open circuits by verifying continuity through the solenoid winding—OL or infinite resistance indicates failed windings.
Perform an actuation test using an advanced scan tool or manual solenoid activation if your diagnostic equipment supports this function. Listen for clicking sounds indicating solenoid plunger movement, and feel for fluid flow through the appropriate hydraulic circuit. No click or flow indicates solenoid failure.
Solenoid Replacement
Most transmission solenoids are mounted on the valve body and can be replaced without removing the transmission from the vehicle. Access typically requires removing the transmission pan, which may necessitate fluid draining and filter replacement.
After accessing the valve body, note solenoid wire routing and connector positions before removal. Remove mounting screws and carefully lift the solenoid from the valve body, taking care not to damage the delicate seal or O-ring. Install new solenoids with fresh seals and O-rings, torquing mounting screws to specification to prevent leaks.
Transmission Fluid Contamination
Solenoid failure often indicates debris contamination from worn clutches, bands, or internal components. Magnetic particles in old transmission fluid can accumulate on solenoid screens and prevent proper operation. If solenoid failure recurs shortly after replacement, internal transmission wear may be introducing debris into the hydraulic system.
Perform a transmission fluid analysis or internal inspection to identify the contamination source. Dark, burnt-smelling fluid or debris on the transmission pan magnet indicates clutch or band wear requiring more extensive repair.
Adaptation After Solenoid Replacement
After solenoid replacement, the TCM must relearn optimal operating parameters. Drive through all gear ranges gently for several drive cycles to allow the TCM to adjust clutch apply pressures and shift timing to compensate for normal production variations in the new solenoid.
Solenoid Types and Operation
Automatic transmissions use several types of solenoids with different operating characteristics. On-off solenoids provide binary control—either full flow or no flow. Variable force solenoids control pressure proportionally based on TCM command. Linear solenoids provide precise position control for applications like line pressure regulation.
Understanding your transmission's solenoid configuration helps with diagnosis. Some solenoids are normally closed (flow when energized), others are normally open (flow when de-energized). This affects how the transmission behaves when a solenoid fails—normally closed solenoids may cause default behaviors that provide limp-home capability.
Solenoid Circuit Diagnostics
Beyond resistance testing, solenoid circuit diagnosis includes checking for shorts to ground, shorts to power, and open circuits. Use a wiring diagram to identify all wires in the solenoid circuit and test each for proper function. Check connector terminals for corrosion or damage that could affect signal quality.
Modern solenoids often share ground circuits with other components. A failed ground can cause multiple symptoms across different circuits. Verify ground integrity by checking resistance from component ground pins to chassis ground—resistance should be less than 1 ohm.