Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 653

7A1–112 AUTOMATIC TRANSMISSION (4L30-E)

DIAGNOSTIC TROUBLE CODE (DTC) 51

ENGINE COOLANT SWITCH SHORT TO GROUND, PLUS OR OPEN

This DTC does NOT flash the CHECK TRANS
indicator and does NOT set the BACKUP MODE.

Circuit Description:

•

The Engine Coolant Temperature is measured by
a sensor in the coolant system. This information
is used by the Engine Control Module (ECM) for
the engine. The ECM provides the information:
Engine Warm to the Transmission Control
Module (TCM) when the ECM measures a
temperature higher than 70°C (158°F).

•

The information is provided using a wire
between the ECM terminal 10 and the TCM
terminal D14. When the engine is warm the ECM
connects its terminal 10 to ground using a Low
Side Driver. When the engine is Cold the ECM
lets this wire open and the TCM pulls it up to 5
volts.

•

When Ignition is ON and Engine is OFF: the ECM
always sends the information “engine cold” even
if the engine is warm. The information is valid
only when the engine is ON.

Diagnostic Aids:

•

This Diagnostic is not an electrical test done by
the TCM but a test between different information
(“logic test”).

•

Detection conditions of engine always cold:
1 Engine seen as cold: wire short to voltage or

open.

2 Transmission Oil Temperature >150°C (302°F)

or more than 20 minutes since last ignition
cycle.

3 Detection conditions need to be present for at

least 25 seconds.

•

Detection conditions of engine always warm:
1 Engine seen as warm: wire short to ground.
2 Transmission Oil Temperature < 0°C (32°F).
3 Without problem on Transmission Tem-

perature sensor then: voltage on A/T Oil
Temperature sensor <4.74 V.

4 Detection conditions need to be present for at

least 6 seconds.

•

Action after the detection time: No action.

•

Recovery conditions: To recover, Engine Coolant
Temperature change information need to be
present for more than 6 seconds.

ENGINE
COOLANT
TEMPERATURE
INPUT

TRANSMISSION
CONTROL
MODULE (TCM)

C-95

ENGINE
COOLANT
TEMPERATURE
OUTPUT

ENGINE
CONTROL
MODULE (ECM)

10

E-61

6

H-25

BRN

BRN

H-25

BLK

BLK

BLK

7

C1(1)

D1(17)

GROUND

D14(30)

D07LW019

AUTOMATIC TRANSMISSION (4L30-E) 7A1–113

DIAGNOSTIC TROUBLE CODE (DTC) 51

ENGINE COOLANT SWITCH SHORT TO GROUND, PLUS OR OPEN

IF: You see a problem:

•

This DTC can be set when there is no problem at
all. This is due to the fact that when the engine
stalls the ignition is still ON then Engine Control
Module (ECM) provides a false information:
engine cold. The Transmission Control Module
(TCM), knowing that the last ignition cycle
happened more than 20 minutes ago, then sets
DTC51.

•

Using the Scan Tool you can check with TECH2:
F0: ENG. TEMP. SW information. When the
engine is cold or when the engine is OFF the
TECH2 should show: COLD. When the engine is
warm the TECH2 should show WARM.

•

This DTC is not very important. In the worst case
it would not allow the Torque Converter Clutch
(TCC) to be applied. This will cause low fuel
economy.

YES

•

Check voltage between connector C-95 terminal D14
and connector C-95 terminal C1 (TCM ground).

•

Ignition switch ON. Engine ON.
Engine warm.

IF: Voltage higher than 5 volts:

NO

There is not currently a problem.
GOTO INTERMITTENT CONDITIONS.

YES

•

There is a short circuit to voltage.

•

Repair. 

NO

IF: Voltage approx. 5 volts:

YES

•

This is an open circuit or the ECM
is not sending the correct
information. See also ECM
information, Section 6E.

•

Repair. 

NO

•

Voltage approx. 0 volts means
that the signal is OK or that
there is a short circuit to
ground.

•

Turn the engine OFF with the
ignition ON.

IF: The voltage goes back to 5
volts:

NO

YES

There is not currently a
problem.
GOTO INTERMITTENT
CONDITIONS.

•

As the voltage is staying at 0
volts, there is a short to
ground.

•

Repair. 

7A1–114 AUTOMATIC TRANSMISSION (4L30-E)

DIAGNOSTIC TROUBLE CODE (DTC) 52

KICK DOWN ALWAYS ON OR SHORT TO GROUND

This DTC does NOT flash the CHECK TRANS
indicator and does NOT set the BACKUP MODE.

Circuit Description:

•

When the driver presses the accelerator pedal
down fully, the kick down switch closes, sending
a ground signal to the Transmission Control
Module (TCM).

•

This information is used to do shifts with a high
Engine Speed RPM.

•

When the kick down switch is closed the Throttle
Position Sensor (TPS) is already at 100%.

Diagnostic Aids:

•

This diagnostic is not an electrical test done by
the TCM but a test between different information
(“logic test”).

•

Detection conditions:
1 Kick down switch ON (short to ground) and

TPS <70%.

2 No malfunction: TPS short to voltage or

ground (DTC21 and DTC22).

3 The conditions need to be present for at least

1 second.

•

Action after the detection time: Kick Down
information not taken into account.

•

Recovery conditions: To recover, Kick Down
needs to be seen as OFF during detection time.

KICK
DOWN
SWITCH
INPUT

TRANSMISSION
CONTROL
MODULE (TCM)

C-96

KICK DOWN
SWITCH

C-94

1

2

C-94

BLU

BLK

BLK

BLK

7

H-25

C1(1)

C-95

D1(17)

GROUND

BLK

B5(17)

D07LW020

AUTOMATIC TRANSMISSION (4L30-E) 7A1–115

DIAGNOSTIC TROUBLE CODE (DTC) 52

KICK DOWN ALWAYS ON OR SHORT TO GROUND

IF: DTC 23 Throttle Position Sensor (TPS) connector
open too:

YES

GOTO DTC 23.

NO

•

Ignition switch ON. Engine OFF.

•

Accelerator pedal not depressed.

•

Connect a voltmeter between connector C-96
terminal B5 and connector C-95 terminal C1 (TCM
ground).

IF: Display approx. 0 volts:

YES

•

Check the wires and connector
and the switch to detect the
short to ground.

•

Repair. 

NO

The problem is
intermittent. GOTO
INTERMITTENT
CONDITIONS.