Symptom/Condition

SYMPTOM/CONDITION:

1992 AC & AY built after February 15, 1992 (MDH 02-15-XX). ALL 1993-1994 and 1995 BUILT BEFORE October 19, 1994 (MDH 10-19-XX).

1. Vehicles that operate frequently at speeds where EMCC usage is engaged (vehicle speeds between 34-41 MPH) may experience early deterioration of the transmission oil (15K-70K miles). Characteristics of deteriorated oil include yellowish brown color, burnt odor, and poor shift quality. Deteriorated transmission fluid may cause harsh upshifts, downshifts, a pronounced shudder during EMCC operation, and/or harsh torque converter clutch engagements. If one or more of these shift characteristics is noted by the customer at relatively low mileage, the TCM should be updated with the latest software and the transaxle fluid must be changed. See Repair Procedure No. 1.

2. If vehicle shudder, engine surge or excessive engine torsional vibration while operating in EMCC (vehicle speeds between 34-41 MPH), transmission operation seems normal, and the transaxle fluid color is normal, the TCM should be updated with the latest software. See Repair Procedure No. 2.

Eliminating EMCC will resolve this symptom/condition. However, if an impending overheat condition is identified by the vehicle PCM or TCM, EMCC operation, as well as shift schedule changes, will be temporarily enabled until the overheat situation is over.

The software calibration used in the 1995 model year 41TE and 42LE TCM is being made available for all vehicles dating back to 1989 MY. Several shift quality improvements, as well as default issues, have been included that will further improve customer satisfaction with prior model vehicles. Some of the more common issues are listed below and are resolved with the new TCM software.

1. Coastdown Tip-In Bump: Vehicle is decelerated to nearly a stop (less than 5 MPH), the driver tips back into the throttle to accelerate, a noticeable bump may be felt.

2. Coastdown Shift Harness: Harsh coastdown shifts on some 4-3, 3-2 and 2-1 downshifts.

3. 1995 LH with the 42LE Transaxle - Sluggishness/Lack of Response: On some early 1995 LH vehicles built prior to October 24, 1994, a perceived lack of power or transmission responsiveness may be encountered under normal operating conditions. The transmission may not release the converter clutch as desired with increased throttle. This occurs in 4th gear from 35 MPH to 50 MPH.

4. 1989-1994 all with 41TE or 42LE: Harsh and/or vehicle shudder at low speeds 3-2 and 2-1 kickdowns at speeds less than 25 MPH.

5. 1993 with 41TE: Poor 3-4 upshifts may occur especially at highway speeds in speed control mode.

6. 1989-1994 with 41TE - Harsh or Slightly Delayed Garage Shifts: Delay is less than 2 seconds and the shift is harsh after the brief delay. NOTE: Delays greater than 2 seconds are caused by transmission hardware malfunction, i.e., valve body, pump, failed lip seals or malfunctioning PRNDL or neutral start switch.

7. 1989-1994 All - Poor Shift Quality After a Battery Disconnect: All transmission learn values are reset to the factory default values if battery power is lost to the TCM. On 1993 and later vehicles, the 1995 software calibration will now retain all learn values in memory after battery disconnect. However. if a transmission is rebuilt or a new transmission or TOM is installed. the quick learn procedure must be performed to reset all values to factory default.

Note:
Before performing the quick learn, it is imperative that the vehicle be shifted into OD with the engine running and the oil level set to the correct level. This procedure will purge the air in the clutch circuits to prevent erroneous clutch volume values which could cause poor initial shift quality.

8. Early 1993 with 41TE and 42LE - Intermittent Speed Control Drop Out: The new service software provides calibration changes to correct this condition (this condition was also covered in Technical Service Bulletin 08-09-93 dated March 12, 1993).

9. 1989-1993 all with the 41TE and 42LE - New added fault code 35 (failure to achieve pump prime) for improved diagnostics, and fault codes 24, 21 and 22 are de-sensitized to reduce erroneous limp-in conditions.

CODE 24 - LOW REVERSE PRESSURE SWITCH CIRCUIT.

Code 24 can get set in error on vehicles where pump prime problems are evident. The new fault code 35 (failure to achieve pump prime) has been added and does not trigger a limp-in condition.

CODE 21 - OD PRESSURE SWITCH CIRCUIT.

Code 21 can be set in error on vehicles with a misadjusted shift cable or if the transaxle is shifted slowly from the OD position to the N position. This typically happens if the vehicle is equipped with a floor shifter and the operator has a tendency to rest his hand on the shift knob, or the if the operator overshoots the OD gate while manually shifting from L or 3 to OD. The new software detects this maneuver and shifts the transaxle into neutral rather than setting the code 21 default and the subsequent limp-in conditions.

CODE 22 AND 24 - PRESSURE SWITCH CIRCUIT.

In low ambient temperatures (below 32 degrees fahrenheit) some 1989 and 1990 model year vehicles may set this fault in error. Condensation can form and freeze in the PRNDL and/or neutral start switch and cause a delay on garage shifts. The new software prevents this fault code from being set in error and causes the transaxle to go into limp-in.

SEE REPAIR PROCEDURE NO. 2 FOR THE ABOVE LISTED CONDITIONS.