controls ISUZU TROOPER 1998 Service Workshop Manual

TRANSMISSION CONTROL SYSTEM (4L30±E)7A1±63
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 control in the Powertrain Control Module
(PCM).
This DTC detects a check sum error. This is a type ªCº
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 CHECK TRANS Lamp.
Conditions For Clearing The MIL/DTC

The PCM will turn off the 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 ªoffº
long enough to power down the PCM.
DTC P1790 ROM Transmission Side Bad Check Sum
StepActionYe sNo
11. Install the scan tool.
2. With the engine ªoffº, turn the ignition switch ªonº.
NOTE: Before clearing DTC(s), use the scan tool to record ªFailure
Recordsº for reference, as data will be lost when the ªClear Infoº
function is used.
3. Record the DTC ªFailure Recordsº.
Was DTC P1790 set?
Go to Step 4Go to Step 2
2Was DTC P1792 set?Go to Step 3Ð
31. Remove the PCM. Refer to Powertrain Control Module (PCM)
in Automatic Transmission (4L30±E) section.
2. Using the ITCS, make a reprogramming the transmission
EEPROM.
Was the reprogramming complete?
Go to Step 5Ð
4Replace the PCM.
Is the replacement complete?
Go to Step 5Ð
51. After the repair is complete, use the scan tool to select ªDTCº,
then ªClear Infoº function and operate the vehicle.
2. Review the scan tool ªDTC Infoº.
Has the last test failed or is the current DTC displayed?
Begin diagnosis
again
Go to Step 1
Repair verified
Exit DTC table

7A1±64
TRANSMISSION CONTROL SYSTEM (4L30±E)
DTC P1792 EEPROM 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 control in the Powertrain Control Module
(PCM).
This DTC detects a check sum error. This is a type ªCº
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 CHECK TRANS Lamp.
Conditions For Clearing The MIL/DTC

The PCM will turn off the 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 ªoffº
long enough to power down the PCM.
DTC P1792 EEPROM Transmission Side Check Bad Check Sum
StepActionYe sNo
11. Install the scan tool.
2. With the engine ªoffº, turn the ignition switch ªonº.
NOTE: Before clearing DTC(s), use the scan tool to record ªFailure
Recordsº for reference, as data will be lost when the ªClear Infoº
function is used.
3. Record the DTC ªFailure Recordsº.
Was DTC P1790 set?
Go to Step 4Go to Step 2
2Was DTC P1792 set?Go to Step 3Ð
31. Remove the PCM. Refer to Powertrain Control Module (PCM)
in Automatic Transmission (4L30±E) section.
2. Using the ITCS, make a reprogramming the transmission
EEPROM.
Was the reprogramming complete?
Go to Step 5Ð
4Replace the PCM.
Is the replacement complete?
Go to Step 5Ð
51. After the repair is complete, use the scan tool to select ªDTCº,
then ªClear Infoº function and operate the vehicle.
2. Review the scan tool ªDTC Infoº.
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±67
DTC P1850 Brake Band Apply Solenoid Malfunction
D07RW009
Circuit Description

The brake band apply solenoid is a normally open
solenoid which controls the flow of fluid for brake band
application. The Powertrain Control Module (PCM)
uses Pulse Width Modulation (PWM) and changes
the duty cycle to control the solenoid. The PCM turns
the solenoid on (energized) and off (deenergized) at a
constant frequency. The length of time the solenoid is
energized during each on/off cycle is called the pulse
width. By varying or ªmodulatingº the pulse width, the
solenoid output pressure is changed. Since the
solenoid is normally open, increasing the pulse width
increases the duty cycle and decreases the output
pressure. PWM control provides smooth band
application without an accumulator. The band is only
applied in first and second gears.

In the event of an electrical failure (open), the
solenoid regulates at the maximum oil flow (0% duty
cycle).

The solenoid is activated by 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 PCM
that acts as a switch between the solenoids and the
supply voltage. The High side of the solenoid is
permanently supplied with voltage. When the ignition
is off, the HSD is turned off.This DTC detects a continuous open or short to ground in
the brake band apply solenoid circuit or the brake band
apply solenoid. This is a type ªDº DTC.
Conditions For Setting The DTC

Battery voltage is between 10 and 16 volts.

Ignition is ªonº, Engine ªrunº.

The PCM commands the solenoid ªonº and the
voltage remains high (B+) or the PCM commands the
solenoid ªoffº and the voltage remains low (zero
volts).

All conditions met in 1.3 seconds.
Action Taken When The DTC Sets

Inhibit brake band apply solenoid.

The PCM will not illuminate the CHECK TRANS
Lamp.
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 ªoffº
long enough to power down the PCM.

8DÐ16 WIRING SYSTEM
Circuit Breaker
The circuit breaker is a protective device designed to
open the circuit when a current load is in excess of rated
breaker capacity. If there is a short or other type of
overload condition in the circuit, the excessive current will
open the circuit between the circuit breaker terminals.
The reset knob (1) pops out when the circuit is open. Push
the reset knob in place to restore the circuit after repairing
it.
Relay
Battery and load location may require that a switch be
placed some distance from either component. This
means a longer wire and a higher voltage drop (1).
The installation of a relay between the battery and the
load reduces the voltage drop (2).
Because the switch controls the relay, amperage through
the switch can be reduced.
Push
LOAD
12LOAD
RELAY
D08RW404
1

8DÐ80 WIRING SYSTEM
Powertrain Control Module (PCM)
General Description
The Powertrain Control Module (PCM) is located in
the passenger compartment.
The PCM constantly monitors the information from
various sensors, and controls the systems that affect
vehicle performance.
The PCM performs the diagnostic function of the
system. It can recognize operational problems, alert
the driver through the Malfunction Indicator Light
(MIL) and store a Diagnostic Trouble Code (DTC) or
DTC(s) which identify the problem areas to aid the
technician in making repairs.
The PCM is designed to process the various input
informations and then sends the necessary
electrical responses to control fuel delivery, spark
timing and other emission control systems. The
input information has an interrelation to more than
one output, therefore, if the one input failed, it could
affect more than one system operation.
Refer to Driveability and Emission in Engine section
and Automatic Transmission in Transmission
section.

8DÐ118 WIRING SYSTEM
QOS and EGR System (4JG2)
General Description
The circuit consists of the starter switch, QOS/EGR
control unit, glow relay, charge relay, fuel cut
solenoid, dropping resistor, thermo sensor, glow
indicator light (meter), glow plug, vehicle speed
sensor, tacho sensor, throttle position sensor, EVRV
and VSV; EGR.
The engine coolant temperature at the time of the
engine start-up is sensed by the thermo sensor to
change the glow time so that the optimum starting
conditions can always be obtained.
The idling speed just after the engine start-up can
also be placed in the most suitable conditions in
accordance with the coolant temperature by the
operation of the delay timer.The indicator timer is activated upon the starter
switch turned to the ON position, and the indicator
light comes on for as much time as suitable for the
engine coolant temperature at the time of the
engine start-up.
EGR system controls the information of NOx by
returning a small amount of exhaust gas from the
intake manifold to the combustion chamber
through the EGR valve.

8DÐ208 WIRING SYSTEM
Stoplight
General Description
The circuit consists of the stoplight, stoplight switch
(vehicles w/o cruise control), brake switch (vehicles
w/ cruise control).
With the brake pedal depressed, the stoplight switch
or the brake switch is turned on to illuminate the
stoplight. The brake switch controls not only the
operation of the stoplight but also the input of the
cruise cancel signals to the cruise control unit.

8DÐ284 WIRING SYSTEM
Anti-lock Brake System (ABS)
General Description
The circuit consists of EHCU (Electronic Hydraulic
Control Unit), wheel speed sensor, GÐsensor,
stoplight switch or brake switch (w/cruise control),
backup light switch, transmission switchÐ1, 2,
indicator light and data link connector.
EHCU controls brake fluid pressure applied to front
and rear wheels to prevent wheels from locking by
using speed sensor and GÐsensor signals.
Based on wheel speed signals from speed sensor,
EHCU activates solenoid valves incorporated into
the control unit to increase, maintain or decrease
brake fluid pressure.
Refer to AntiÐlock Brake System in Brakes section.

8D Ð 464 WIRING SYSTEM
A/T Shift Indicator
General Description
The circuit consists of mode switch, A/T shift indica-
tor control unit and A/T shift indicator (meter).
A/T shift indicator control unit controls to illuminate
A/T shift indicator light according to signals from
mode switch.

SUPPLEMENTAL RESTRAINT SYSTEM9J±5
1. Energy Reserve Ð The SDM maintains 24±Volt Loop
Reserve (24VLR) energy supply to provide
deployment energy when ignition voltage is lost in a
frontal crash.
2. Frontal Crash Detection Ð The SDM monitors
vehicle velocity changes to detect frontal crashes
which are severe enough to warrant deployment.
3. Air Bag Deployment Ð When a frontal crash of
sufficient force is detected, the SDM will cause
enough current to flow through the air bag assembly
to deploy the air bag.
4. Malfunction Detection Ð The SDM performs
diagnostic monitoring of SRS electrical components
and sets a diagnostic trouble code when a
malfunction is detected.
5. Frontal Crash Recording Ð The SDM records
information regarding SRS status during frontal
crash.
6. Malfunction Diagnosis Ð The SDM displays SRS
diagnostic trouble codes and system status
information through the use of a scan tool.
7. Driver Notification Ð The SDM warns the vehicle
driver of SRS malfunctions by controlling the ªAir
Bagº warning lamp.
The SDM is connected to the SRS wiring harness by a
24±pin connector. This harness connector uses a
shorting clip across certain terminals in the contact area.
This shorting clip connects the ªAIR BAGº warning lamp
to ground when the SDM harness connector is
disconnected or CPA (Connector Position Assurance) is
not inserted even if completely connected. This will
cause the ªAIR BAGº warning lamp to come ªONº steady
whenever the ignition switch is at the ON or START
positions with the SDM disconnected.
827RW044
Legend
(1) SDM
(2) SRS Harness
(3) Connector Position Assurance
ªAir Bagº Warning Lamp
Ignition voltage is applied to the ªAIR BAGº warning lamp
when the ignition switch is at the ON or START positions.
The SDM controls the lamp by providing ground with a
lamp driver. The ªAIR BAGº warning lamp is used in the
SRS to do the following:
1. Verify lamp and SDM operation by turn on 3.5
seconds and then turns ªOFFº when the ignition
switch is first turned ªONº.
2. Warn the vehicle driver of SRS electrical system
malfunctions which could potentially affect the
operation of the SRS. These malfunctions could
result in nondeployment in case of a frontal crash or
deployment for conditions less severe than intended.
The ªAIR BAG º warning lamp is the key to driver
notification of SRS malfunctions. For proper lamp
operation, refer to the ªSRS Diagnostic System Checkº in
this section.
821RW037
SRS Coil Assembly
The SRS coil assembly consists of two current carrying
coils. This is attached to the steering column and allow
rotation of the steering wheel while maintaining
continuous contact of the driver deployment loop to the
driver air bag assembly.
There is a shorting clip on the yellow 2±pin connector near
the base of steering column which connects the SRS coil
to the SRS wiring harness.
The shorting clip shorts to the SRS coil and driver air bag
assembly when the yellow 2±pin connector is
disconnected. The circuit to the driver air bag assembly is
shorted in this way to help prevent unwanted deployment
of the air bag when servicing the steering column or other
SRS components.