Dodge 2001 Ram 1500 Owner's Manual page 2346

BR/BE
ELECTRONIC GOVERNOR (Continued)
Fig. 70 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
temperature is at, or above, 10°C (50°F) during nor-
mal city or highway driving. A third curve is used
during wide-open throttle operation. The fourth curve
is used when driving with the transfer case in low
range.
OPERATION
Compensation is required for performance varia-
tions of two of the input devices. Though the slope of
the transfer functions is tightly controlled, offset may
vary due to various environmental factors or manu-
facturing tolerances.
The pressure transducer is affected by barometric
pressure as well as temperature. Calibration of the
zero pressure offset is required to compensate for
shifting output due to these factors.
Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absence
of sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the cold period of operation.
AUTOMATIC TRANSMISSION - 47RE
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to produce
governor pressure. The average current supplied to the
solenoid controls governor pressure. One amp current
produces zero kPa/psi governor pressure. Zero amps sets
the maximum governor pressure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts (DC).
The PCM controls the ground side of the solenoid using
the governor pressure solenoid control circuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conventional
governor can delay shifts, resulting in higher than nor-
mal shift speeds and harsh shifts. The electronically
controlled low temperature governor pressure curve is
higher than normal to make the transmission shift at
normal speeds and sooner. The PCM uses a temperature
sensor in the transmission oil sump to determine when
low temperature governor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous stand-
alone electronic module. This facilitated the develop-
ment of a load adaptive shift strategy - the ability to
alter the shift schedule in response to vehicle load con-
dition. One manifestation of this capability is grade
hunting prevention - the ability of the transmission
logic to delay an upshift on a grade if the engine does
not have sufficient power to maintain speed in the
higher gear. The 3-2 downshift and the potential for
hunting between gears occurs with a heavily loaded
vehicle or on steep grades. When hunting occurs, it is
very objectionable because shifts are frequent and
accompanied by large changes in noise and acceleration.
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