o/d light comes on shortly after trans temp light comes on
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If the trans temp is not getting above 50 degrees
the computer will not engage OD or TCC per the manual:
TRANSMISSION FLUID TEMPERATURE
THERMISTOR
Transmission fluid temperature readings are supplied
to the transmission control module by the thermistor
(Fig. 6). The temperature readings are used to
control engagement of the fourth gear overdrive
clutch, the converter clutch, and governor pressure.
Normal resistance value for the thermistor at room
temperature is approximately 1000 ohms.
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10°C (50°F).
If fluid temperature exceeds 126°C (260°F), the
PCM causes a 4-3 downshift and engage the converter
clutch. Engagement is according to the third
gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel
illuminates when the shift back to third occurs. The
transmission will not allow fourth gear operation
until fluid temperature decreases to approximately
110°C (230°F).
The thermistor is part of the pressure sensor and
is immersed in transmission fluid at all times.
So maybe your going slow enough around town to
keep it above 50 degrees but on the highway it cools
down to much and disengages.
Where you live?
Dave
the computer will not engage OD or TCC per the manual:
TRANSMISSION FLUID TEMPERATURE
THERMISTOR
Transmission fluid temperature readings are supplied
to the transmission control module by the thermistor
(Fig. 6). The temperature readings are used to
control engagement of the fourth gear overdrive
clutch, the converter clutch, and governor pressure.
Normal resistance value for the thermistor at room
temperature is approximately 1000 ohms.
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10°C (50°F).
If fluid temperature exceeds 126°C (260°F), the
PCM causes a 4-3 downshift and engage the converter
clutch. Engagement is according to the third
gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel
illuminates when the shift back to third occurs. The
transmission will not allow fourth gear operation
until fluid temperature decreases to approximately
110°C (230°F).
The thermistor is part of the pressure sensor and
is immersed in transmission fluid at all times.
So maybe your going slow enough around town to
keep it above 50 degrees but on the highway it cools
down to much and disengages.
Where you live?
Dave