Torque Converter Clutch Control Circuit

THEORY OF OPERATION:
When in 2nd, 3rd, or 4th gear, the Torque Converter Clutch (TCC) can be locked when certain conditions are met-The TCC piston is electronically modulated by increasing the-duty cycle of the L-R/TCC solenoid until the torque converter slip difference (difference between engine and turbine speed) is within 60 RPM. Then the L-R/TCC solenoid is fully energized (FEMCC = 100% duty cycle). For 97 model year, torque converter sip is monitored in FEMCC to ensure adequate clutch capacity.
a. The transmission must be in PEMCC, with the input speed greater than 1750 RPM. The TCC/L-R solenoid must achieve it's maximum duty cycle and still not be able to pull the engine speed within 60 RPM of input speed.
b. For 97 model year only, if the transmission is in FEMCC and the engine can slip the TCC by more than 100 RPM (engine speed - Input speed) for 10 seconds.

The code will be set if one of these event's happen three times at a throttle angle less than 30 degrees.

LIMP-IN:
NO

WHEN MONITORED/SET CONDITIONS:
During Partial Electronically Modulated Converter Clutch (PEMCC) operation (also during FEMCC for 97 model year only).

TRANSMISSION EFFECTS:
89-96 model year - EMCC will not be attempted again after TCM reset (key "off" then back to "run"). The transmission will not go into limp-in mode.

97 model year - EMCC will still be available after code is set. MIL will illuminate after 5 minutes of accumulated limp in FEMCC. The transmission will attempt normal operation (no-limp-in) even after the MIL is illuminated.

POSSIBLE CAUSES:
- Worn pump bushing and/or failed torque converter- both should be replaced during a rebuild with code 38 present.
- Valve body - lock-up accumulator diameter out of specification.