This page will serve to show you how to obtain the latest software update for your A604 / 41TE / 42LE transmission.
Most of the information in this page is paraphrased from TSB 18-24-95.
Basically Chrysler made several software revisions to later Transmission Control Module (TCM). They then made these revisions available to all models dating back to the 1989 model year. Issues corrected include the following:
1. Coastdown Tip-In Bump: Vehicle is decelerated almost to a stop (less than 8 MPH), then the driver tips back into the throttle to accelerate, a noticeable bump may be felt.
2. Coastdown Shift Harshness: Harsh coastdown shifts on some 4-3, 3-2 and 2-1 downshifts.
3. 1995 LH with 42LE Transaxle - Sluggishness/Lack of Response: On some early 1995 LH vehicles built prior to Oct. 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 with 41TE & 42LE Transaxles: Harsh shifts and/or vehicle shudder during 3-2 or 2-1 kickdowns at speeds less than 25 MPH.
5. 1993 with 41TE Transaxle: Harsh 3-4 upshifts may occur, especially at highway speeds, while using the speed control.
6. 1989-1994 with 41TE Transaxle - Harsh/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 with 41TE & 42LE Transaxles- Poor Shift Quality After a Battery Disconnect: All transmission learned values are reset to the factory default values if battery power is lost to the TCM. The new 1995 calibration will now retain all learned values in memory after battery disconnect. However, if a transmission is rebuilt or a new transmission or TCM is installed, the Quick Learn procedure must be performed to calibrate Clutch Volume Indexes (CVI) on 1993 and later vehicles (1992 and prior vehicle cannot be Quick Learned).
8. Early 1993 with 41TE & 42LE Transaxle - Intermittent Speed Control Drop Out: The new service calibration change corrects this condition (this condition was also covered in Technical Service Bulletin 08-09-93 dated Mar. 12, 1993).
9. 1989-1993 with 41TE & 42LE Transaxles - New fault code 35 (failure to achieve pump prime) has been added for Improved diagnostic capability, and fault codes 21, 22 and 24 are de-sensitized to reduce erroneous limp-in conditions.
Code 21 (OD Pressure Switch Circuit) - 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 operator has a tendency to rest his hand on the shift lever, or 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 code a 21 fault and the subsequent limp-in conditions.
Code 22 and 24 (2-4 and L-R Pressure Switch Circuits) - In low ambient temperatures (below 32° F or 0° C) 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 the transaxle going into the limp-in mode.
Code 24 (Low Reverse Pressure Switch Circuit) - Can get set in error on vehicles where pump prime problems exist. The new fault code 35 (failure to achieve pump prime) has been added and does not trigger a limp-in condition.
There are two ways to update your TCM. Either you can reflash it or purchase a TCM with the calibration already on it. Note that 89-92 TCMs without cooling fins cannot be flashed and most 93+ TCMs with cooling fins can be flashed. Of particular note, Chrysler lists the following TCMs cannot be flashed:
4686174, 4686175, 4686208, 4686209, 4686223, 4686224, 4686490 or 4686491
They most likely explicitly stated these cannot be flashed because they may have fins, confusing some technicians.
To this date, the latest revision for these transmissions is the 1995 revision. The following chart shows the latest revision for North American vehicles:
The following chart shows the latest revision for Export Vehicles:
Of particular note for the above chart, those silly Mexicans got the A604 for both 2.5L Turbo 1 and Turbo 2 applications. Also, I have no idea what the "A5 AL" body code is.
I will not cover how to flash the computer, as many DIY mechanics do not have the proper tools to do so. However, with these cars being as old as they are many of these computers are popping up on ebay with the latest revision. Simply searching for the software ID or the re-manufactured part number will come up with a variety of results.
Also, when purchasing a new 93-95 re-manufactured TCM, the pinion factor must be set with a DRB. Below is the specific warning from Chrysler:
(MY 93-95 Only, Except LH & FJ Vehicles) The vehicle speed readings for
the speedometer are taken from the output speed sensor. The transmission
control module must be calibrated to reflect the different combinations of
equipment available. A procedure has been developed called Pinion Factor.
It allows the technician to set the transmission control module initial setting
so that the speedometer readings will be correct.
This procedure must be performed if the transmission control module has
been replaced.
Failure to perform this procedure will result in a “NO SPEEDOMETER
OPERATION” condition.
NOTE: The DRB III Scan Tool MUST be used to perform the Pinion
Factor Procedure described above. This procedure can be performed
at any authorized Chrysler Corporation Dealer.
Lastly, of particular note is the 93-95 model year computers. These computers can, and must, be put into quick learn mode when they are installed into the vehicle. The problem, however, is that most mechanics lack the proper tools to do so. When you install used TCMs into your vehicle note that the transmission may exhibit erratic behavior as it tries to adapt to your driving and the new transmission.