Isuzu Rodeo UE. Manual - part 489

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–75

DTC P1790 ROM Transmission Side Bad Check Sum

Circuit Description

Transmission Side Read Only Memory (ROM) and
Electronically Erasable Programmable Read Only
Memory (EEPROM) is an electronic circuit that controls
the transmission controls in the Powertrain Control
Module (PCM).
This DTC detects a check sum error. This is a type “B”
DTC.

Conditions For Setting The DTC

Detects check sum error for 1 second.

Action Taken When The DTC Sets

Maximum line pressure.

Immediate landing to 4th gear.

Inhibit TCC engagement.

The PCM will illuminate the Malfunction Indicate
Lamp (MIL) and CHECK TRANS Lamp.

Conditions For Clearing The MIL/DTC

The PCM will turn off the MIL and CHECK TRANS
Lamp after three consecutive ignition cycles without a
failure reported.

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.

DTC P1790 ROM Transmission Side Bad Check Sum

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

Emission in

Engine 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 “Failure
Records” for reference, as data will be lost when the “Clear Info”
function is used.

3. Record the DTC “Failure Records”.

Was DTC P1790 set?

Go to Step 5

Go to Step 3

Was DTC P1792 set?

Go to Step 4

—

1. Remove the PCM. Refer to Powertrain Control Module (PCM)

in Automatic Transmission (4L30–E) section.

2. Using the ITCS reprogram the transmission EEPROM.

Was the reprogramming complete?

Go to Step 6

—

Replace the PCM.

Is the replacement complete?

Go to Step 6

—

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

then “Clear Info” function and operate the vehicle.

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

7A1–76 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P1792 EEPROM Transmission Side Bad Check Sum

Circuit Description

Conditions For Setting The DTC

Detects check sum error for 1 second.

Action Taken When The DTC Sets

Maximum line pressure.

Immediate landing to 4th gear.

Inhibit TCC engagement.

The PCM will illuminate the Malfunction Indicate
Lamp (MIL) and CHECK TRANS Lamp.

Conditions For Clearing The MIL/DTC

The PCM will turn off the MIL and CHECK TRANS
Lamp after three consecutive ignition cycles without a
failure reported.

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.

DTC P1792 EEPROM Transmission Side Bad Sum

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

Emission in

Engine 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 “Failure
Records” for reference, as data will be lost when the “Clear Info”
function is used.

3. Record the DTC “Failure Records”.

Was DTC P1790 set?

Go to Step 5

Go to Step 3

Was DTC P1792 set?

Go to Step 4

—

1. Remove the PCM. Refer to Powertrain Control Module (PCM)

in Automatic Transmission (4L30–E) section.

2. Using the ITCS reprogram the transmission EEPROM.

Was the reprogramming complete?

Go to Step 6

—

Replace the PCM.

Is the replacement complete?

Go to Step 6

—

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

then “Clear Info” function and operate the vehicle.

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

TRANSMISSION CONTROL SYSTEM (4L30–E)

7A1–77

DTC P1835 Kickdown Switch Always On

D07RW015

Circuit Description

When the driver presses the accelerator pedal down
fully, the kickdown switch closes, sending a ground
signal to the Powertrain Control Module (PCM).

This information is used to perform shifts at high
engine speed.

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

This DTC detects a closed kickdown switch when TP
angle is less than 70%.

This is a type “D” DTC.

Conditions For Setting The DTC

No TP DTCs P0122 or P0123.

TP angle is less than 70%.

Kickdown switch is “on”.

All conditions met for 1 second.

Action Taken When The DTC Sets.

Kickdown mode control is off.

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 the wiring harness for a short to ground
between the PCM and kickdown switch.

Check the kickdown switch for failure.

Check kickdown adjustment.

Test Description

The numbers below refer to the step numbers on the
diagnostic chart:
2. This test checks for short to ground or kickdown

switch failure.

4. This test checks for regulation kickdown switch.

7A1–78 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P1835 Kickdown Switch Always On

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

Emission in

Engine section

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

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

3. Record the DTC “Failure Records”.

Does the scan tool display “Kickdown switch” “low” (closed
switch)?

Go to Step 3

Go to Step 4

1. Turn the ignition “off”.
2. Disconnect the C3 (BLUE) PCM connector.
3. Using the J39200 DVOM, check a continuity between PCM

connector terminal C3–F11 and ground.

Is there a continuity?

Go to Step 5

Go to Step 8

The TP angle goes from 0% to 100% with the accelerator pedal
depressed.

Does the kickdown switch “on” when TP angle is below 70%?

Go to Step 6

Go to Diagnostic

Aids

1. Disconnect the kickdown switch connector C–29.
2. Using the J39200 DVOM, check a continuity between

terminals C29–1 and C29–2.

Is there a continuity?

Go to Step 7

Go to Step 9

Adjust the kickdown switch.

Does the kickdown switch “on” when TP angle is above 95%?

Go to Step 10

—

Replace the kickdown switch.

Is the replacement complete?

Go to Step 10

—

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

Is the replacement complete?

Go to Step 10

—

Repair the short to ground in circuit LT BLUE.

Is the repair complete?

Go to Step 10

—

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

then “Clear Info” function and ensure the following condition is
met:
The torque converter stator temperature switch circuit does not
indicate a hot mode when the transmission fluid temperature is
less than 60

C (140

F) for at least 5 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

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