Powertrain Control Module (Pcm); Circuit Description; Diagnostic Aids - Isuzu 2000 Trooper Workshop Manual

Powertrain Control Module (PCM)

Diagnosis
To read and clear diagnostic trouble codes, use a Tech 2.
IMPORTANT: Use of a Tech 2 is recommended to clear
diagnostic trouble codes from the PCM memory.
Diagnostic trouble codes can also be cleared by turning
the ignition "OFF" and disconnecting the battery power
from the PCM for 30 seconds. Turning off the ignition and
disconnecting the battery power from the PCM will cause
all diagnostic information in the PCM memory to be
cleared. Therefore, all the diagnostic tests will have to be
re-run.
Since the PCM can have a failure which may affect only
one circuit, following the diagnostic procedures in this
section will determine which circuit has a problem and
where it is.
If a diagnostic chart indicates that the PCM connections
or the PCM is the cause of a problem, and the PCM is
replaced, but this does not correct the problem, one of the
following may be the reason:
D There is a problem with the PCM terminal
connections. The terminals may have to be removed
from the connector in order to check them properly.
D EEPROM program is not correct for the application.
Incorrect components or reprogramming the PCM
with the wrong EEPROM program may cause a
malfunction and may or may not set a DTC.
D The problem is intermittent. This means that the
problem is not present at the time the system is being
checked. In this case, refer to the Symptoms portion
of the manual and make a careful physical inspection
of all component and wiring associated with the
affected system.
D There is a shorted solenoid, relay coil, or harness.
Solenoids and relays are turned "ON" and "OFF" by
the PCM using internal electronic switches called
drivers. A shorted solenoid, relay coil, or harness will
not damage the PCM but will cause the solenoid or
relay to be inoperative.
Multiple PCM Information Sensor
DTCs Set

Circuit Description

The powertrain control module (PCM) monitors various
sensors to determine the engine operating conditions.
The PCM controls fuel delivery, spark advance,
transmission operation, and emission control device
operation based on the sensor inputs.
The PCM provides a sensor ground to all of the sensors.
The PCM applies 5 volts through a pull–up resistor, and
determines the status of the following sensors by
monitoring the voltage present between the 5–volt supply
and the resistor:
D The engine coolant temperature (ECT) sensor
D The intake air temperature (IAT) sensor
D The transmission fluid temperature (TFT) sensor
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
The PCM provides the following sensors with a 5–volt
reference and a sensor ground signal:
1
D The exhaust gas recirculating (EGR) pintle position
D sensor
D The manifold absolute pressure (MAP) sensor
D The throttle position (TP) sensor 1
D The acceleration position (AP) sensor 1
D The acceleration position (AP) sensor 3
D The Vapor Pressure Sensor
2
D The Crank position (CKP) sensor
D The Camshaft Position (CMP) Sensor
D The throttle position (TP) sensor 2
D The acceleration position (AP) sensor 2
The PCM monitors the separate feedback signals from
these sensors in order to determine their operating
status.

Diagnostic Aids

IMPORTANT: Be sure to inspect PCM and engine
grounds for being secure and clean.
A short to voltage in one of the sensor input circuits may
cause one or more of the following DTCs to be set:
D P0425
D P0108, P1106
D P0406
D P1120, P1515, P1221, P1516, P1635
D P1275, P1639, P1271, P1273
D P1285, P1272, P1273
D P0336, P0337
D P0341, P0342
D P1220, P1515, P1221, P1515, P1516
D P1280, P1271, P1272
IMPORTANT: If a sensor input circuit has been shorted
to voltage, ensure that the sensor is not damaged. A
damaged sensor will continue to indicate a high or low
voltage after the affected circuit has been repaired. If the
sensor has been damaged, replace it.
An open in the sensor ground circuit between the PCM
and the splice will cause one or more of the following
DTCs to be set:
D P0425
D P0108,P1106
D P0406
D P1120, P1515, P1221, P1516, P1635
D P1275, P1639, P1271, P1273
D P1285, P1272, P1273
D P0336, P0337
D P0341, P0342
D P1220, P1515, P1221, P1515, P1516
D P1280, P1271, P1272
A short to ground in the 5–volt reference A or B circuit will
cause one or more of the following DTCs to be set:
6E–77