Code P1746 relates to torque converter clutch (TCC) malfunction in your 2024 Chrysler Voyager. The torque converter clutch is a mechanism that locks the engine to the transmission input shaft mechanically, eliminating torque converter slip and improving fuel efficiency. When this system fails, drivers notice increased fuel consumption, transmission overheating, or shuddering during acceleration.
The torque converter consists of an impeller (pump), turbine, and stator housed in a sealed case filled with transmission fluid. The TCC is essentially a clutch disc mounted between the engine and transmission input. When engaged, it locks these components together for direct mechanical power transfer.
TCC engagement is controlled by a solenoid that meters transmission fluid into or out of the converter clutch piston. When conditions are met—correct gear, vehicle speed typically above 45 mph, light throttle position, and transmission temperature within range—the TCM commands the TCC solenoid to apply the clutch.
TCC Shudder Diagnosis
A common symptom of TCC problems is a shudder or vibration during light acceleration at highway speeds, particularly when the lockup clutch should be engaging. This shudder occurs when the TCC is partially applied or releasing inconsistently, causing slip between the converter cover and turbine.
Begin diagnosis by checking transmission fluid level and condition. Low fluid or degraded fluid can prevent proper TCC operation. Examine the transmission cooler lines at the radiator for blockages or damage, as the cooler is in series with the TCC hydraulic circuit and contamination can prevent proper operation.
TCC Solenoid Testing
Locate the TCC solenoid on the valve body and test its resistance. The TCC solenoid typically operates in the 10-20 ohm range, though specifications vary by manufacturer. Check for internal shorts by measuring resistance between the solenoid terminal and case ground—continuity indicates damaged windings.
Perform a TCC solenoid actuation test using a scan tool to verify the TCM can command the solenoid. If no clicking is heard or felt, or if the symptom persists during manual actuation, the solenoid is likely failed. Some systems use pulse-width modulation for TCC control, so listen for rapid clicking rather than a single engagement sound.
Converter Replacement
In severe cases, torque converter clutch shudder persists despite solenoid replacement. This indicates converter internal damage—worn damper springs, scored thrust surfaces, or failed needle bearings. The torque converter cannot be serviced separately and must be replaced as a complete assembly.
Converter replacement requires transmission removal and fluid service, as the converter cannot be drained or flushed. After replacement, the TCM adaptation procedure must be performed to optimize TCC engagement characteristics for the new converter.
TCC Lockup Control Strategy
Understanding TCC operation helps diagnose intermittent problems. Most systems disengage the TCC during wide-open throttle acceleration, braking, and low-speed operation. If shudder occurs only under specific conditions, the problem may be in the TCM's control logic rather than the mechanical components.
Torque Converter Construction and Function
The torque converter is a complex hydraulic component that transfers engine power to the transmission through fluid coupling. Beyond its basic function, the converter includes the TCC mechanism, a lockup clutch that physically connects the engine and transmission input shaft. The converter also contains a stator that multiplies engine torque during low-speed operation.
Inside the converter, transmission fluid is forced through the turbine by the impeller (pump), creating hydraulic flow that transfers torque. The stator redirects this fluid flow to improve efficiency at low speeds. As vehicle speed increases, the stator freewheels, allowing more efficient direct flow between impeller and turbine.
TCC Shudder and Vibration Analysis
TCC shudder typically manifests as a vibration felt through the steering wheel, seat, or floorpan during light cruise load conditions. The shudder occurs at a specific speed range when the TCC attempts to engage. If the shudder persists after engagement, the converter clutch is slipping. If shudder occurs just before engagement, the issue is likely in the apply sequence.
Distinguishing TCC shudder from engine or driveline vibration is important for accurate diagnosis. TCC shudder typically occurs at steady speed with light throttle, disappears when accelerating or decelerating, and may be temperature-dependent. Driveline vibrations usually change with acceleration or occur at specific engine speeds.
TCC solenoid PWM Control
Modern TCC solenoids use pulse-width modulation for smooth engagement. The TCM rapidly switches the solenoid on and off to gradually increase clutch pressure and prevent engagement shock. Failed PWM control causes harsh lockup engagement that feels like a transmission bump.
Testing TCC solenoid PWM operation requires an advanced scan tool that can display solenoid duty cycle. Watch the duty cycle increase as the TCM commands engagement—the pattern should be smooth and progressive. Erratic duty cycle changes or failure to reach expected values indicates solenoid or circuit problems.