Isuzu 2000 Trooper Workshop Manual page 1357

6E–488
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1640 Driver-1-Output Circuit Fault (ODM)
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 fail. 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 A history DTC P1640 will clear after 40 consecutive
warm-up cycles occur without a fault.
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.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
4. The Tech 2 Driver Module Status indicates the PCM
pin that is affected.
9. 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.
11.A short to ground on the ignition side of the
component will blow the fuse. Since the fuse was
checked in Step 2, a short to ground would be
between the affected component and the PCM.