A/T - 41TE/42LE Interactive Cruise Control
NO: 08-15-95 Rev. AGROUP: Electrical
DATE: Sep. 8, 1995
SUBJECT:
41TE/42LE Transaxle
Downshifting/Upshifting While
Speed Control is Engaged
(Interactive Speed Control)
NOTE:
THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 08-15-95, DATED APR. 7, 1995, WHICH SHOULD BE REMOVED FROM YOUR FILES. THE REVISIONS ADD MODELS AND INFORMATION. REVISIONS ARE HIGHLIGHTED WITH **ASTERISKS**.
MODELS:
1993 - 1995 (AA) Spirit/Acclaim/LeBaron Sedan
1993 (AC) Dynasty/New Yorker/New Yorker Salon
1993 (AG) Daytona
1993 - 1995 (AJ) LeBaron Coupe/LeBaron Convertible
1993 - 1994 (AP) Shadow/Shadow Convertible/Sundance
1993 - 1995 (AS) Town & Country/Caravan/Voyager
1993 (AY) Imperial/New Yorker Fifth Avenue
1993 - 1995 (ES) Chrysler Voyager (European Market)
1995 - **1996 (FJ) Avenger/Sebring/Talon**
1995 - **1996** (JA) Cirrus/Stratus
**1996 (JX) Sebring Convertible**
1993 - **1996** (LH) Concorde/Intrepid/LHS/New Yorker/Vision
1996 (NS) Town & Country/Caravan/Voyager
1996 (GS) Chrysler Voyager (European Market)
NOTE:
THIS BULLETIN APPLIES TO THE LISTED 1993 AND 1994 VEHICLES ONLY IF THEY HAVE HAD THE TRANSMISSION CONTROL MODULE (TCM) FLASHED OR REPLACED PER TECHNICAL SERVICE BULLETIN **18-27-94 DATED JAN. 30, 1995, 18-27-95 REV. A DATED JAN. 30, 1995 OR 18-24-94 DATED JUN. 23, 1995.**
DISCUSSION:
**Interactive (interactive meaning "communication between the Powertrain Control Module (PCM) and the Transmission Control Module (TCM) is taking place) speed control avoids unnecessary shifting for smoother, quieter operation and, when downshifts are required, makes the shifts smoother.
Additional features have been added to interactive speed control for the 1996 model year, downshift delay and grade hunting prevention (shifting back and forth between gears while climbing a steep grade) between 2nd and 3rd gears. **
The following is an explanation of how the interactive speed control effects 41TE and 42LE transaxle operation:
WHEN CLIMBING A GRADE - The interactive speed control will try to maintain the set speed by increasing the throttle opening. If opening the throttle **alone cannot maintain the set speed and the vehicle speed to drops more than 3 mph below the set speed,** the transaxle will downshift to 3rd gear. If the vehicle continues to lose speed, the transaxle will downshift further until a gear that can maintain the set speed is selected. After the vehicle encounters a less steep grade or has crested the grade (reduced the load on the powertrain) and can maintain the set speed at a reduced throttle position, the transmission will upshift as appropriate until the set speed can be maintained in Overdrive.
**Downshift Delay - To reduce the number and frequency of downshifts when operating in hilly/mountainous country, downshift delay features have been added for the 1996 41TE and 42LE equipped vehicles. While operating, interactive speed control delays or avoids downshifts by applying up to nearly wide open throttle without the TCM scheduling a downshift. If the interactive speed control is not engaged or the throttle is manually overridden by the driver while interactive speed control is engaged, the downshift delay feature is not activated.
Torque convertor lock and unlock shifts are not affected by the downshift delay feature and will occur at the same throttle angle at a given speed regardless of whether interactive speed control is engaged or not.
Grade Hunting - Since the 1991 model year, 41TE and 42LE equipped vehicles have had the grade hunting feature for the 3rd to Overdrive upshift. The TCM identifies the powertrain loading conditions and selects the proper gear to maintain the current vehicle speed. Under moderate loading conditions the transaxle will stay in 3rd gear until the top of the grade is reached or the powertrain loading is reduced. If conditions are more severe, hunting between 2nd and 3rd could occur on 1991 - 1995 model year vehicles.
For 1996 all 41TE and 42LE equipped vehicles have the grade hunting feature for the 2nd to 3rd gear upshift. If powertrain loading is severe, the transaxle may shift into 2nd gear and remain there until powertrain loading is reduced, then a 2nd to 3rd gear upshift will be scheduled. Grade hunting features always operate regardless of whether or not the interactive speed control is engaged. If the interactive speed control is not engaged and powertrain loading is not reduced, the driver may have to completely lift off of the throttle before an upshift will occur. If the driver does lift off the throttle to induce an upshift under these conditions, vehicle speed will reduce and the Overdrive to 3rd and 3rd to 2nd gear downshifts will reoccur when the throttle is reapplied. If grade hunting is repeatedly induced by the driver transaxle damage may result.**
WHEN DESCENDING A GRADE **(OVERSPEED REDUCTION) - The overspeed reduction feature was first introduced with all 1995 model year 41TE and 42LE applications (1993 and 1994 41TE and 42LE equipped vehicles that have had either TSB 18-27-94 dated Jan. 30, 1995, 18-27-94 Rev. A dated Jan. 30, 1995 or 18-24-95 dated June 23, 1995 also have this feature). The overspeed reduction feature helps maintain the interactive speed control set speed when descending a grade.
First TCM senses the interactive speed control is set. Then** the interactive speed control will try to maintain the set speed by reducing or closing the throttle opening. If closing the throttle (a Throttle Position Sensor (TPS) signal of 2 degrees or less is considered closed throttle) is not enough to keep the vehicle within 3 MPH over the set speed, the transaxle will downshift to 3rd gear. The transaxle will not downshift below 3rd gear to try to maintain the set speed. **After the downshift to 3rd gear, the interactive speed control continues its normal operation. Conditions leading to a return to Overdrive are monitored by the TCM. Once conditions are identified that grade hunting between 3rd and Overdrive is unlikely, the transaxle will shift into Overdrive and resume normal operation.**
If the downshift to 3rd gear has taken place, pushing the brake pedal will disengage the interactive speed control but the transaxle will stay in 3rd gear. The transaxle will upshift to Overdrive when the TCM receives a TPS signal of approximately 5 degrees or more.
If the downshift to 3rd gear has taken place and the interactive speed control is still engaged, the transaxle will upshift to Overdrive when the TCM receives a TPS signal of approximately 8 degrees or more for approximately 3 seconds or more with the vehicle at the set speed or greater.
NOTE:
1993, 1994 AND 1995 (BUILT ON OR BEFORE 10124195, MDH 10-24-XX) LH VEHICLES USE 8 DEGREES TPS SIGNAL. 1995 LH VEHICLES (BUILT AFTER 10124195, MDH 10-24-XX) OR ANY LH VEHICLE THAT HAS HAD TECHNICAL SERVICE BULLETIN **18-27-94 DATED JAN. 30, 1995, 18-27-94 REV. A, DATED JAN. 30, 1995 OR 18-24-95 DATED JUN. 23, 1995.** PERFORMED ON IT USES A 3 DEGREES TPS SIGNAL THAT IMPROVES ON/OFF THROTTLE FEEL WHEN THE INTERACTIVE SPEED CONTROL ACTIVATES THE THROTTLE OPENING AS THE GRADE FLATTENS OUT.
If the downshift to 3rd gear has taken place and the interactive speed control is disengaged using the ON/OFF button or the CANCEL button, the transaxle will upshift to Overdrive after an approximate 2 second delay.
POLICY: Information Only