Electronically Modulated Converter Clutch (EMCC)

The use of partial Electronically Modulated Converter Clutch (EMCC) is available at speeds as low as 17 mph, giving the advantage of reducing heat build-up to the transmissions, while buffering the rest of the powertrain from engine torsional vibrations. Full EMCC is utilized under certain conditions to improve gas mileage. Both full EMCC or partial EMCC are also scheduled to help reduce heat build-up of the transaxle or its fluid under certain driving conditions.

Torque converter full EMCC and partial EMCC availability depends on many different input conditions. These include shift lever position (OD, 3, L), current gear range (2nd, 3rd, or 4th), transmission fluid temperature, engine coolant temperature, input speed and throttle angle.

The TCM output logic states controlling the torque converter are the following:

- No EMCC - Torque converter clutch is OFF.

- Partial EMCC - Modulates the LR/CC solenoid (duty cycle) to obtain partial torque converter clutch application. Partial EMCC operation is maintained until full EMCC logic is called for and actuated.

- Full EMCC - Increases the LR/CC solenoid duty cycle to full "ON" after partial EMCC control brings the engine speed within the desired slip range of transaxle input speed relative to engine rpm (crankshaft speed).

- Gradual-to-No EMCC - Designed to soften the change from full or partial EMCC to no EMCC, at mid-throttle, by gradually decreasing the LR/CC solenoid duty cycle.

A malfunction of the EMCC system is detected from a
lengthy partial EMCC operation near the maximum allowable duty cycle, except at heavy throttle. If a diagnostic trouble code is reported, the TCM will not operate the torque converter clutch. It remains unapplied until the next restart. DTC 38 is stored in memory.

The TCM is provided with EMCC inhibits to prevent EMCC from occurring under specific conditions. The following are times when EMCC WILL NOT occur:

- Transaxle Temperature - When the transaxle temperature range is warm, cold or supercold, EMCC is inhibited (kept from occurring). In the event of a CCD Bus failure on vehicles not equipped with the Transmission Range Sensor, -3° F is substituted for the initial temperature. This initial value is incremented up to normal transmission operating temperature based on transmission loading, by monitoring torque converter slip, and input shaft speed. This results in delayed EMCC operation under start-up conditions.

- Brake Signal (ON) - Cancels and prevents EMCC as long as a brake signal is ON.

- Solenoid Switch Valve - If a Solenoid Switch Valve (SSV) malfunction is detected, EMCC will not occur. A SSV diagnostic trouble code will only be stored if the transaxle operating temperature range is hot, and the malfunction occurs at least three times. The fault counter is reset during the start routine.

- EMCC Fault - Any reported EMCC diagnostic trouble code prevents any type of EMCC from occurring.

- Engine Coolant Temperature - If the engine coolant temperature drops below 150°F because of a defective Engine Coolant Temperature (ECT) Sensor, coolant sensor wiring or a stuck open thermostat, EMCC is canceled. PCM diagnostic trouble code 17 (Engine coolant temperature stays low too long) has been known to cause the transaxle to overheat (transmission fluid temperature over 250° F). This causes the TCM to initiate the overheat shift schedule.