A/T - 41TE/42LE Lock-Up Control System Changes
Date: 1996Technical Bulletin # 346
^ Transmission:
41TE/42LE
^ Subject:
Lock-up control system changes, A/C
compressor engagement complaints
^ Application: Chrysler
41TE / 42LE
Lock-up Control System Changes,
Air Conditioner Compressor Engagement Complaints.
DTC 73
In 1995, the lock-up control system was changed so that partial lock-up, or Electronically Modulated Converter Clutch (EMOC) apply would no longer occur under any conditions. This was done to eliminate TCC chaffer. However, with lock-up now fully engaged (instead of being allowed to slip a small amount), the A/C compressor could be felt engaging and disengaging with a noticeable thump feel through the vehicle whenever the A/C was operating.
To correct this problem, all 1996 model controllers have been reprogrammed to allow EMCC (partial torque converter slip) to occur just before the A/C compressor is either engaged or released. This allows the TCC to slip through the A/C compressor engagement or release, then fully re-engage after the compressor engage or release is complete. The torque converter therefore absorbs the thump of compressor engagement or release.
If the TCM detects a rapid fluctuation of turbine speed during EMCC operation, it interprets this as TCC slip: DTC 73 is set and partial slip, or EMCC operations are not allowed for the following 20 lock-up engagement cycles. After 20 cycles have completed, EMCC will once again be allowed.
NOTE:
If any part of a repair or service to a 1996 4iTE or 42LE causes the torque converter to subsequently chatter during partial slip (EMCC) it will be detected and EMCC will be canceled. This will most likely cause a complaint of the A/C compressor engagement and disengagement being much more noticeable since the transmission work had been done.
If a complaint of noticeable A/C operations occurs after transmission work is performed, with a DTC 73 in memory, it should be treated like a TCC chaffer problem. Cooler flow should be checked, Chrysler 7176 ATF should be used, and all other steps necessary to diagnose TCC chatter should be performed.