Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1578

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–37

DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input

D07RY00029

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

Battery voltage is between 10 and 16 volts.

Ignition is “on”.

TFT sensor indicating a voltage less than 0.4 volts.

All conditions met for 20 seconds.

Action Taken When The DTC Sets

Transmission default temperature will be:

C (176

F) if engine temperature code is set.

100

C (212

F) if engine temperature is warm.

C (176

F) if engine run time is greater than 5

minutes.

C (69.8

F) if engine run time is less than 5

minutes.

The PCM will not illuminate the Malfunction Indicator
Lamp (MIL).

Conditions For Clearing The DTC

The DTC can be cleared from the PCM history by
using a scan tool.

The DTC will be cleared from history when the vehicle
has achieved 40 warmup cycles 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.

Diagnostic Aids

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.

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.

When diagnosing for a possible intermittent short or
open condition, move the wiring harness while
observing test equipment for a change.

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.

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.

7A1–38 TRANSMISSION CONTROL SYSTEM (4L30–E)

Resistance Chart

Resistance (k

)

–40

672

176

2.5

120

248

0.78

150

304

0.37

DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input

Step

Action

Yes

Were you sent here from the “Powertrain On–Board Diagnostic
(OBD) System Check”?

Go to Step 2

Go to OBD

System Check

Refer to

Driveability and

Emissions in

Engine section

Perform the transmission fluid checking procedure. Refer to
Checking Transmission Fluid Level and Condition in Automatic
Transmission (4L30–E) section

Was the fluid checking procedure performed?

Go to Step 3

Refer to

Checking

Transmission

Fluid Level and

Condition in

Automatic

Transmission

(4L30–E) section

1. Install the scan tool.
2. With the engine “off”, turn the ignition switch “on”.

NOTE: Before clearing DTC(s), use the scan tool to record “Freeze
Frame” and “Failure Records” for reference, as data will be lost
when the “Clear Info” function is used.

3. Record the DTC “Freeze Frame” and “Failure Records”.

Does the scan tool display a TFT sensor signal voltage less than
0.4 volts?

Go to Step 4

Go to Diagnostic

Aids

1. Turn the ignition “off”.
2. Disconnect the transmission 7–way connector E–54.
3. Turn the ignition “on”.

Does the TFT signal voltage change to match the voltage 4.92
volts?

Go to Step 5

Go to Step 10

Using the J39200 DVOM, measure the resistance between
terminals E54–4(F) and E54–1(E).

Is the resistance within specifications? (See Resistance Chart.)

Go to Diagnostic

Aids

Go to Step 6

1. Disconnect the transmission 7–way connector E–54.
2. Using the J39200 DVOM, measure the resistance between

terminals E54–4(F) and E54–1(E).

Is the resistance within specifications? (See Resistance Chart.)

Go to Diagnostic

Aids

Go to Step 7

1. Remove the transmission oil pan. Refer to Transmission Oil

Temperature Sensor (Main Case) in Automatic Transmission
(4L30–E) section.

2. Check the internal wiring harness for a short to ground.

Was a problem found?

Go to Step 9

Go to Step 8

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–39

DTC P0712 Transmission Fluid Temperature (TFT) Sensor Circuit Low Input (Cont’d)

Step

Yes

Action

1. Disconnect the internal wiring harness at the TFT sensor.
2. Measure the resistance of the TFT sensor.

Is the resistance within specifications? (See Resistance Chart.)

Go to Diagnostic

Aids

Go to Step 9

Replace the TFT Sensor.

Is the replacement complete?

Go to Step 13

—

Check circuit RED/BLK for a short to ground.

Was a problem found?

Go to Step 13

Go to Step 11

Check the PCM for faulty connections.

Was a problem found?

Go to Step 13

Go to Step 12

Replace the PCM. Refer to Powertrain Control Module (PCM) in
Automatic Transmission (4L30–E) section.

Is the replacement complete?

Go to Step 13

—

1. After the repair is complete, use the scan tool to select “DTC”,

then “Clear Info” function and ensure the following conditions
are met:
TFT sensor indicates a voltage greater than 0.33 volts for 2
seconds.

2. Review the scan tool “DTC info”.

Has the last test failed or is the current DTC displayed?

Begin diagnosis

again

Go to Step 1

Repair verified
Exit DTC table

7A1–40 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P0713 Transmission Fluid Temperature (TFT) Sensor Circuit High Input

D07RY00029

Circuit Description

The TFT sensor is a thermistor 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
and the PCM will sense high signal voltage. As the
transmission fluid temperature warms to the normal
operating temperature of 100

C (212

F), the sensor

resistance becomes less and the voltage decreases to
about 1.5 to 2 volts.
This DTC detects a continuous open or short to power in
the TFT signal circuit or the TFT sensor. This is a type “D”
DTC.

Conditions For Setting The DTC

Battery voltage is between 10 and 16 volts.

Ignition is “on”.

TFT sensor indicating a voltage greater than 4.86
volts.

All conditions met for 20 seconds.

Action Taken When The DTC Sets

Transmission default temperature will be:

C (176

F) if engine temperature code is set.

100

C (212

F) if engine temperature is warm.

C (176

F) if engine run time is greater than 5

minutes.

C (69.8

F) if engine run time is less than 5

minutes.

The PCM will not illuminate the Malfunction Indicator
Lamp (MIL).

Conditions For Clearing The DTC

The DTC can be cleared from the PCM history by
using a scan tool.

The DTC will be cleared from history when the vehicle
has achieved 40 warmup cycles 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.

Diagnostic Aids

When diagnosing for a possible intermittent short or
open condition, move the wiring harness while
observing test equipment for a change.

Scan tool displays transmission fluid temperature in
degrees. After transmission is operating, the
temperature should rise steadily to about 100

(212

F), then stabilize.

The temperature to resistance value scale may be
used to check the TFT sensor at the various
temperature levels to evaluate the possibility of a
“skewed” (mis–scaled) sensor.

A “skewed” sensor could result in hard shifts or TCC
complaints.

Test Description

The numbers below refer to the step numbers on the
diagnostic chart:
3. This check verifies problem in the TFT sensor circuit.
4. This test simulates a TFT sensor DTC P0712. If the

PCM recognizes the low signal voltage (high
temperature), and the scan tool displays 146

(295

F) or greater, the PCM and wiring are OK.

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