Isuzu Trooper (1998-2002 year). Service manual — part 336
6E–257
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1618 Serial Peripheral Interface (SPI) PCM
Interprocessor Communication Error
Circuit Description
The serial peripheral interface (SPI) communication is
used internally by the PCM to send messages between
the engine processor and the automatic transmission
processor. Included in each message sent between the
two-processors is a checksum of the message. Both the
engine processor and automatic transmission processor
will compare this check sum value with the calculated
value. If the checksums don’t match, the processor will
view the new data as being corrupted and ignore the
values. The processor will then use the previous
message. The receiving processor will then send a
message to the sending processor informing it that it’s
last message was corrupted.
Conditions for Setting the DTC
D
Battery voltage is above 9.0 V for 2 seconds.
D
The PCM detects an internal program fault (check sum
of data communications error).
D
Check sum fault present for 3 out 6 seconds.
D
No TCM resets for 2 seconds.
Action Taken When the DTC Sets
D
The PCM will flash the “Check Trans” lamp the first
time the fault is detected.
D
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
D
The automatic transmission will operate in the “safety
mode” to protect the mechanical parts of the
transmission. Shift quality and/or gear changes may
not be normal.
Conditions for Clearing the MIL/DTC
D
DTC P1618 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
DTC P1618 – Serial Peripheral Interface (SPI) PCM Interprocessor
Communication Error
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to Step 2
Go to
OBD
System
Check
2
Is the EEPROM calibration the latest version
available?
—
Go to
Step 4
Go to
Step 3
3
Reprogram the PCM with the latest available
calibrations.
Does DTC 1618 re-appear when the
OBD System
Check is repeated?
—
Go to
Step 4
Repair
completed
4
Replace the PCM.
IMPORTANT: The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?
—
Verify repair
—
6E–258
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1625 PCM Unexpected Reset
Circuit Description
The powertrain control module (PCM) monitors
unexpected PCM reset. This will not turn on MIL light on,
only records code DTC P1625.
Conditions for Setting the DTC
D
Clock or COP reset.
Action Taken When the DTC Sets
D
The PCM will not illuminate the malfunction indicator
lamp (MIL).
D
The PCM will store conditions which were present
when the DTC was set as Failure Records only. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC
D
DTC P1625 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
D
P1625 alone stored does not need diagnosis. Clear
DTC code.
6E–259
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1640 Driver-1-Input High Voltage
Circuit Description
Output driver modules (ODMs) are used by the
powertrain control module (PCM) to turn “ON” many of
the current-driven devices that are needed to control
various engine and transmission functions. Each ODM is
capable of controlling up to 7 separate outputs by
applying ground to the device which the PCM is
commanding “ON.”
Unlike the Quad Driver Modules (QDMs) used in prior
model years, ODMs have the capability of diagnosing
each output circuit individually. DTC P1640 set indicates
an improper voltage level has been detected on an ODM
output.
Since A/C is an option, No A/C will cause the air
conditioning clutch relay output to always fault. If a fault is
seen on the air conditioning clutch relay output, it will not
be logged as a fault until the A/C request input interrupts a
high voltage, indicating that A/C has been installed.
Conditions for Setting the DTC
D
Ignition “ON.”
D
Engine running.
D
No DTC 1618.
D
Ignition voltage is above 13.2 volts for 4 seconds.
D
Output voltage does not equal ignition voltage when
output is “OFF” or output voltage is not less than 1 volt
when output is “ON.”
D
Above conditions occur for at least 1 second.
Action Taken When the DTC Sets
D
The PCM will not illuminate the malfunction indicator
lamp (MIL).
D
The PCM will store conditions which were present
when the DTC was set as Failure Records only. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC
D
DTC P1640 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
D
Poor connection at PCM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
D
Damaged harness – Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the PCM, turn the ignition “ON” and observe a
voltmeter connected to the suspect driver circuit at the
PCM harness connector while moving connectors and
wiring harnesses relates to the MIL. A change in
voltage will indicate the location of the fault.
D
Poor connection at component – Examine for
damaged connectors, unplugged connector, or
damaged terminals at the following locations:
Instrument cluster harness, canister purge solenoid,
A/C clutch relay. An open ignition feed circuit at any of
these components will cause DTC P1640 to be set.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
The following PCM pins are controlled by output driver
modules (ODMs):
D
A13 – “Check Engine Lamp”
D
A14 – SVS (”Check Trans”)
D
B14 – A/C Clutch
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
6. The Tech 2 Driver Module Status indicates the PCM
pin that is affected.
11. The Tech 2 may indicate “short circuit” even when
the problem is an open circuit. The cause of an
open circuit may be in the component itself-lamp,
purge, solenoid, or A/C compressor relay.
13.A short to ground on the ignition side of the
component will blow the fuse. Since the fuse was
checked in Step 4, a short to ground would be
between the affected component and the PCM.
6E–260
ENGINE DRIVEABILITY AND EMISSIONS
DTC P1640 – Driver-1-Input High Voltage
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
1. Ignition “ON,”engine “OFF.”
2. Install the Tech 2.
3. Review and record Tech 2 Failure Records data.
4. Operate the vehicle within Failure Records
conditions as noted.
5. Use the Tech 2 to indicate DTC P1640.
Does the Tech 2 indicate DTC P1640?
—
Go to
Step 3
—
3
Check the fuse for the driver circuit that was shown as
faulty.
Was the fuse blown?
—
Go to
Step 4
Go to
Step 5
4
1. Check for a short to ground between the fuse and
the affected component.
2. Replace the fuse after making any necessary
repairs.
Is the action complete?
—
Verify repair
—
5
Disconnect the PCM connector for the affected driver
circuit.
Is there any damage to the PCM pin or connector?
—
Go to
Step 6
Go to
Step 7
6
Repair the damaged pin or terminal.
Is the action complete?
—
Verify repair
—
7
Were either of the lamp circuits for “Check Engine” or
“Check Trans.” indicated as faulty by the Tech 2?
—
Go to
Step 8
Go to
Step 14
8
1. Leave the PCM connector for the lamp driver circuit
disconnected.
2. Ignition “ON.”
3. Using a DVM, check the voltage at the PCM
connector for the affected lamp driver circuit.
Was the voltage equal to the specified value?
B+
Go to
Step 16
Go to
Step 9
9
1. Ignition “ON.”
2. Check for battery voltage at the fuse for the affected
lamp circuit.
Was battery voltage available at the fuse?
—
Go to
Step 11
Go to
Step 10
10
Repair the open circuit between the ignition switch and
the fuse.
Is the action complete?
—
Verify repair
—
11
1. Ignition “OFF.”
2. Disconnect the PCM connector for the affected
driver terminal.
3. Connect an ohmmeter between a good ground and
the PCM connector for the affected driver.
Did the ohmmeter indicate continuity?
—
Go to
Step 12
Go to
Step 13
12
Repair the short to ground between the affected
component and is PCM driver terminal.
Is the action complete?
—
Verify repair
—
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