Workshop Manual

7A1–36
TRANSMISSION CONTROL SYSTEM (4L30–E)
DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input
D07R200004
Circuit Description
The TFT sensor is a thermister that controls the signal
voltage to the PCM. The PCM supplies a 5–volt reference
signal to the sensor on circuit RED/BLK. When the
transmission fluid is cold, the sensor resistance is high.
The PCM detects high signal voltage. As the
transmission fluid temperature 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. With transmission fluid over temperature
and DTC P0218 also set, check the transmission cooling
system.
This DTC detects a continuous short to ground in the TFT
signal circuit or the TFT sensor. This is a type “D” DTC.
Conditions For Setting The DTC
B Battery voltage is between 10 and 16 volts.
B Ignition is “on”.
B TFT sensor indicating a voltage less than 0.4 volts.
B All conditions met for 20 seconds.
Action Taken When The DTC Sets
B Transmission default temperature will be:
80°C (176°F) if engine temperature code is set.
100°C (212°F) if engine temperature is warm.
80°C (176°F) if engine run time is greater than 5
minutes.
21°C (69.8°F) if engine run time is less than 5
minutes.
B The PCM will not illuminate the Malfunction Indicator
Lamp (MIL).
Conditions For Clearing The DTC
B The DTC can be cleared from the PCM history by
using a scan tool.
B The DTC will be cleared from history when the vehicle
has achieved 40 warmup cycles without a failure
reported.
B 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.
Diagnostic Aids
B Check harness routing for a potential short to ground
in circuit RED/BLK. Scan tool TFT display should rise
steadily to about 100°C (212°F), then stabilize.
B Inspect the wiring for poor electrical connection at the
PCM and transmission 7-way connector. Look for
possible bent, backed out, deformed or damaged
terminals. Check for weak terminal tension as well.
Also check for a chafed wire that could short to bare
metal or other wiring. Inspect for a broken wire inside
the insulation.
B When diagnosing for a possible intermittent short or
open condition, move the wiring harness while
observing test equipment for a change.
B The temperature to resistance value scale may be
used to test the TFT sensor at the various
temperature levels to evaluate the possibility of a
“skewed” (mis–scaled) sensor.
A “skewed” sensor could result in delayed garage
shifts or TCC complaints.
B Verify customer driving habits, trailer towing, etc.
Test Description
The numbers below refer to the step numbers on the
diagnostic chart:
3. This test checks for a short to ground or a “skewed”
sensor.
4. This test checks for an internal fault within the
transmission by creating an open.