Hummer H1 Service Manual page 256

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DTC P0712 Transmission Fluid Temperature
(TFT) Sensor Circuit - Low Input
(High Temperature Indicated)
Circuit Description
The transmission fluid temperature (TFT) sensor is a ther-
mister that controls signal voltage to the PCM. The PCM sup-
plies a 5-volt reference signal to the sensor. When the
transmission fluid is cold, sensor resistance is high. The PCM
detects high signal voltage. As the transmission fluid tempera-
ture increases to the normal operating temperature of 100° C
(212° F), the sensor resistance becomes less and the voltage
decreases to 1.5 to 2 volts.
This DTC detects a continuous short to ground in the tempera-
ture signal circuit or the sensor itself.
Conditions For Setting The DTC
• Ignition is "on."
• TFT sensor indicating a voltage less than 0.3 volts.
• All conditions met for 10 seconds.
05745159
TORQUE
CONVERTER
PRESSURE
CLUTCH
CONTROL
SOLENOID
SOLENOID
(TCC)
(PCS)
D C S
C34
C32-F C32-E
C32-G
C27-C15 C27-C7 C28-C5
PCS PCS TCC PWM
LOW HIGH SOLENOID
CONTROL
Transmission/Transfer Case
HOT IN RUN
AND START
FUSE 2A
10A
EXTERIOR
C33-F
C34-E
TRANSMISSION
FLUID
TEMPERATURE
SENSOR
1-2 SHIFT
(TFT)
SOLENOID
(1-2)
2-3 SHIFT
SOLENOID
(2-3)
B A M
C32-D C32-C C32-J
C28-C6 C28-C4 C29-B12
2-3 SS 1-2 SS SENSOR
CONTROL CONTROL GROUND
POWERTRAIN
CONTROL
MODULE
(PCM)
Action Taken When The DTC Sets
• Transmission default temperature will be 140° C (275° F).
NOTE: Scan tool will not display default temperature.
• The PCM will illuminate the warning light.
Conditions For Clearing The DTC
• The PCM will turn off the warning light after three con-
secutive ignition cycles without a failure reported.
• The DTC can be cleared using the scan tool. The DTC
will be when the vehicle has achieved 40 warm-up cy-
cles without a failure reported.
• The PCM will cancel the DTC default actions when the
fault no longer exists and the ignition is cycled "off"
long enough to power down the PCM.
L
C32-H
C27-C9
TFT
SENSOR
SIGNAL
5-57