A/T - Intermittent 2nd Gear and Reverse Only After Start
NO: 21-08-96GROUP: Transmission
DATE: May 24, 1996
SUBJECT:
Intermittent 2nd Gear And Reverse Only Operation After Initial Start-Up.
MODELS:
1996 (FJ) Avenger/Sebring/Talon
1996 (GS) Chrysler Voyager (European Market)
1996 (JA) Cirrus/Stratus/Breeze
1996 (JX) Sebring Convertible
1996 (LH) Concorde/Intrepid/Vision/LHS
1996 (NS) Town & Country/Caravan/Voyager
NOTE:
THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE 41TE/AE OR 42LE (TRS ONLY) AUTOMATIC TRANSMISSION.
DISCUSSION:
After vehicle start-up, the transmission may operate in 2nd and Reverse gear only for the first few minutes of operation and then resume normal shifting. The Transmission Control Module (TCM) may be sensing an open circuit in the transmission temperature sensor circuit and indicating to the TCM that the transmission is extremely cold (i.e. below -16 deg F). This erroneous temperature signal will cause the transmission to stay in 2nd gear until the transmission temperature indicates a value greater than -12 deg F.
Vehicles that have this concern usually set transmission Diagnostic Trouble Code (DTC) 74 (Calculated Oil Temperature In Use). Once transmission DTC 74 is set, the TCM will not attempt to use the transmission temperature sensor but will use the calculated oil temperature routine which was used in all 41TE1AE and 42LE applications built prior to 1996 MY (SEE THE 41TE1AE 42LE POWERTRAIN DIAGNOSTIC SUPPLEMENT PUBLICATION NO. 81-699-96074 AND REFER TO SECTION 7.3 TRANSMISSION OPERATION AND SHIFT SCHEDULING AT VARIOUS SUMP TEMPERATURES). Once DTC 74 is set, the TCM will use the calculated oil temperature routine for 35 OBD II warm-up starts after the fault was set. IF CALCULATED OIL TEMPERATURE IS BEING USED, THE VEHICLE WILL OPERATE NORMALLY, HOWEVER THE CONDITION MAY RETURN AFTER 35 OBD II WARM-UP STARTS WHEN THE TCM ATTEMPTS TO USE THE TRANSMISSION TEMPERATURE SENSOR FOR INPUT AGAIN.
When diagnosing a transmission DTC 74, the following issues must be fully understood otherwise you may not correct the concern.
1) Conditions to set transmission DTC 74 - The TCM must detect intermittent or out of range data from the transmission temperature sensor circuit for THREE CONSECUTIVE KEY STARTS for the DTC to be set. - Setting transmission DTC 74 will enable the Calculated Oil Temperature routine to initialize the transmission oil temperature at start-up for 35 OBD II warm-up starts. After the 35 OBD II warm-up starts, the TCM will attempt to use the temperature sensor for every start until transmission DTC 74 is reset.
2) Invalid temperature Data - In a given key start prior to setting transmission DTC 74, if intermittent or out of range data is detected by the TCM1 then the calculated oil temperature routine is used for that start and is initialized from the last known temperature prior to the intermittent or out of range data being detected by the TCM. This can result in 2nd or Reverse gear only operation if the transmission temperature sensor indicates a start-up temperature below -16° F (which occurs if the temperature sensor circuit resistance is high, but not quite an open circuit). No DTC is set unless it happens to be the third consecutive key start with invalid data identified. Consequently, the technician may not know if the TCM is using the temperature sensor or the calculated oil temperature routine for shift scheduling.
3) Clearing transmission DTC 74 - CLEARING DTC's DOES NOT ENABLE THE TCM TO USE THE TRANSMISSION TEMPERATURE SENSOR. The TCM remembers the last time transmission DTC 74 was set and will not attempt to use the temperature sensor until after 35 OBD II starts since transmission DTC 74 was set regardless if the fault code was cleared by the DRB III or not. However, PERFORMING A BATTERY DISCONNECT WILL ENABLE THE TCM TO USE THE TRANSMISSION TEMPERATURE SENSOR. In order to verify that the problem has been corrected, the TCM requires that the temperature sensor circuit provide intermittent or out of range data for 3 consecutive key starts before transmission DTC 74 will be reset.
DIAGNOSIS:
Use the diagnostic pages for any vehicles that have a transmission DTC 74. The 96/97 41TE/AE 42LE Powertrain Diagnostic Manual will include DTC 74 trouble code tests. Page 23 of the 1996 41TE/AE 42LE Powertrain Diagnostic Manual Supplement (Publication No. 81-699-96074) includes additional information on DTC 74.
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