Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 646

7A1–84 AUTOMATIC TRANSMISSION (4L30-E)

DIAGNOSTIC TROUBLE CODE (DTC) 26

SUPPLY VOLTAGE TOO HIGH

This DTC flashes the CHECK TRANS indicator and
sets the BACKUP MODE.

Circuit Description:

The ignition voltage of Transmission Control
Module (TCM) terminals A7 and A8 is monitored by
the TCM and when the voltage is too high (approx.
16 volts) the DTC26 is stored and the BACKUP
MODE is set.

Diagnostic Aids:

•

This Diagnostic is an electrical test done by the
TCM.

•

Detection conditions:
1 Ignition voltage measured between TCM

terminal A7 or A8 and ground C1 is higher
than 15.5 volts.

2 The condition needs to be present for at least

1 second.

•

Action after the detection time : BACKUP MODE

•

Recovery conditions: To recover, ignition voltage
<

=15.5 volts.

BATTERY

FUSE

ENGINE
CONTROL
MODULE
(ECM)

BATTERY INPUT

EB-12
10A

EB-14
20A

RELAY &
FUSE BOX

X-18

ECM
MAIN
RELAY

E-61

E-60

BATTERY
INPUT

A4
(4)

C1
(1)

D1
(17)

TRANSMISSION
CONTROL MODULE
(TCM)

—

RED/
GRN

GRN

H-25

RED/BLU

BLU/RED

A7
(7)

BLK

C-95

C-96

A8
(8)

GROUND

IGNITION
INPUT

D07LW010

AUTOMATIC TRANSMISSION (4L30-E) 7A1–85

DIAGNOSTIC TROUBLE CODE (DTC) 26

SUPPLY VOLTAGE TOO HIGH

•

Ignition switch ON. Engine OFF.

•

Connect voltmeter between B+ and B- terminals of
battery.

IF: Display greater than 15.5 volts:

•

Engine running.

•

Connect voltmeter between B+ and B- terminals of
battery.

IF: Display between 3 to 15.5 volts:

Check battery.

Check regulator.

The problem is
intermittent.
GOTO
INTERMITTENT
CONDITIONS.

YES

•

Ignition switch OFF.

•

Disconnect Transmission Control
Module (TCM) connector C-95 and
C-96.

•

Ignition switch ON. Engine ON.

•

Connect voltmeter between
connector C-96 terminals A7 and
connector C-95 terminal C1.

IF: Display higher than 15.5 volts:

7A1–86 AUTOMATIC TRANSMISSION (4L30-E)

DIAGNOSTIC TROUBLE CODE (DTC) 31

SOLENOID A SHORT TO GROUND OR OPEN

SHIFT
SOLENOID A
CONTROL

GROUND

TRANSMISSION
CONTROL
MODULE (TCM)

SHIFT
SOLENOID
A

SHIFT
SOLENOID
B

BAND
APPLY
SOLENOID

AUTOMATIC
TRANSMISSION

M-7

3(D)

4(C)

C-96

YEL/GRN

H-23

H-25

BLK

A2(2)

C-95

C12(12)

C1(1)

D1(17)

GROUND

BRN/WHT

YEL/GRN

BRN/WHT

This DTC flashes the CHECK TRANS indicator and
sets the BACKUP MODE.

Circuit Description:

•

The solenoid A is a simple ON/OFF solenoid
located in the main case valve body. The
solenoid is the normally closed-type. In second or
third gear the Transmission Control Module
(TCM) energizes the solenoid to open a fluid inlet
port. When the port is open, fluid pressure
actuates the shift valve.

•

The solenoid is activated by a current. This
current is produced by applying a voltage to one
side (the High side) and a ground to the other
side (Low side).

•

The High Side Driver (HSD) is a circuit of the TCM
that acts as a switch between the solenoids and
the supply voltage. The High side of the solenoid
is permanently supplied with voltage, except in
BACKUP MODE or when ignition is OFF the HSD
is turned OFF.

•

The TCM continually monitors the solenoid
connection to its Low Side Driver (LSD) for either
low or high voltage. The LSD is a circuit of the
TCM that acts as a switch between the solenoid
and ground. When the solenoid is commanded
ON the TCM is switching the solenoid to ground.

•

There are two tests of the LSD: When the engine
is cranked (DTC82) and when the ignition is
turned ON (DTC31).

•

When the ignition is turned ON, and before the
engine is cranked, the TCM activates the shift
solenoids (A, B and Band) to check for short
circuits or open circuits. To do so the gear is set
to 4th, 3rd, 1st, 1st with band apply, 4th with no
HSD. Each one of the 5 tests requires 0.15
second. If the engine is cranked before the end of
all tests, the remaining tests are not done.

Diagnostic Aids:

•

This Diagnostic is an electrical test done by the
TCM.

•

Detection conditions:
1 The solenoid low side connected to TCM

terminal A2 is shorted to ground or open.

2 The test is only done when ignition is ON.
3 Engine Speed < 480 RPM (not cranked) and

Output Speed = 0 RPM.

4 The conditions need to be present for 0.15 to

1.03 second after ignition switch ON.

•

Action after the detection time: BACKUP MODE.

•

Recovery conditions: To recover, do an IGNITION
CYCLE.

D07LW011

•

Ignition switch OFF.

•

Disconnect Transmission Control Module (TCM)
connector C-95 and C-96.

•

Connect ohmmeter between connector C-95 terminal
C12 and connector C-96 terminal A2.

IF: Display between 17.5 and 18.5 ohms?

•

Check for faulty connector or
wiring between terminal A2
and ground.

•

Repair.

YES

AUTOMATIC TRANSMISSION (4L30-E) 7A1–87

DIAGNOSTIC TROUBLE CODE (DTC) 31

SOLENOID A SHORT TO GROUND OR OPEN

YES

•

Connect ohmmeter between connector C-96
terminal A2 and connector C-95 terminal C1
(TCM ground).

IF: Short circuit:

Check for an open circuit between connector C-
96 terminal A2 and connector C-95 terminal C12.
IF: Wiring problem?

The problem is intermittent.
GOTO INTERMITTENT
CONDITIONS.

The problems is
intermittent.
GOTO INTERMITTENT
CONDITIONS.

Replace the solenoid A.

Repair.

•

Disconnect solenoid A connector.

•

IF: Ohmmeter displays between 17.5 and 18.5
ohms on the solenoid A terminals:

Content .. 644 645 646 647 ..