Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1529

6E2–567

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

An open Bank 1 HO2S 1 signal circuit will set a DTC
P0134 and the Tech 2 will display a constant voltage
between 400-500 mV. A constant voltage below 300 mV
in the sensor circuit (circuit grounded) will set DTC
P0131. A constant voltage above 800 mV in the circuit will
set DTC P0132. Faults in the Bank 2 HO2S 1 signal
circuit will cause DTC 0154 (open circuit), DTC P0151
(grounded circuit), or DTC P0152 (signal voltage high) to
set. A fault in the Bank 1 HO2S 1 heater circuit will cause
DTC P0135 to set. A fault in the Bank 2 HO2S 1 heater
circuit will cause DTC P0155 to set. The PCM can also
detect HO2S response problems. If the response time of
an HO2S is determined to be too slow, the PCM will store
a DTC that indicates degraded HO2S performance.

060RY00127

Catalyst Monitor Heated Oxygen Sensors

Three-way catalytic converters are used to control
emissions of hydrocarbons (HC), carbon monoxide (CO),
and oxides of nitrogen (NOx). The catalyst within the
converters promotes a chemical reaction. This reaction
oxidizes the HC and CO present in the exhaust gas and
converts them into harmless water vapor and carbon
dioxide. The catalyst also reduces NOx by converting it to
nitrogen. The PCM can monitor this process using the
Bank 1 HO2S 2 and the Bank 2 HO2S 2 heated oxygen
sensors. The Bank 1 HO2S 1 and the Bank 2 HO2S 1
sensors produce an output signal which indicates the
amount of oxygen present in the exhaust gas entering the
three-way catalytic converter. The Bank 1 HO2S 2 and
the Bank 2 HO2S 2 sensors produce an output signal
which indicates the oxygen storage capacity of the
catalyst. This indicates the catalyst’s ability to efficiently
convert exhaust gases. If the catalyst is operating
efficiently, the Bank 1 HO2S 1 and the Bank 2 HO2S 1
signals will be more active than the signals produced by
the Bank 1 HO2S 2 and the Bank 2 HO2S 2 sensors.
The catalyst monitor sensors operate the same as the
fuel control sensors. The Bank 1 HO2S 2 and the Bank 2
HO2S 2 sensors’ main function is catalyst monitoring, but
they also have a limited role in fuel control. If a sensor
output indicates a voltage either above or below the 450
mV bias voltage for an extended period of time, the PCM

will make a slight adjustment to fuel trim to ensure that
fuel delivery is correct for catalyst monitoring.
A problem with the Bank 1 HO2S 2 signal circuit will set
DTC P0137, P0138, or P0140, depending on the specific
condition. A problem with the Bank 2 HO2S 2 signal
circuit will set DTC P0157, P0158, or P0160, depending
on the specific condition. A fault in the heated oxygen
sensor heater element or its ignition feed or ground will
result in lower sensor response. This may cause
incorrect catalyst monitor diagnostic results.

TS24067

TS23365A

Legend

(1) Bank 1 Sensor 1 (Fuel Control)
(2) Catalytic Converter
(3) Bank 1 Sensor 2 (Catalyst Monitor)
(4) Bank 2 Sensor 1 (Fuel Control)
(5) Bank 2 Sensor 2 (Catalyst Monitor)

Intake Air Temperature (IAT) Sensor

The intake air temperature (IAT) sensor is a thermistor
which changes its resistance based on the temperature of
air entering the engine. Low temperature produces a high

6E2–568

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

resistance of 100,000 ohms at –40

C (–40

F). High

temperature causes low resistance of 70 ohms at 130

(266

F) . The PCM supplies a 5-volt signal to the sensor

through a resistor in the PCM and monitors the signal
voltage. The voltage will be high when the incoming air is
cold. The voltage will be low when the incoming air is hot.
By measuring the voltage, the PCM calculates the
incoming air temperature. The IAT sensor signal is used
to adjust spark timing according to the incoming air
density.
The Tech 2 displays the temperature of the air entering
the engine. The temperature should read close to the
ambient air temperature when the engine is cold and rise
as underhood temperature increases. If the engine has
not been run for several hours (overnight), the IAT sensor
temperature and engine coolant temperature should read
close to each other. A fault in the IAT sensor circuit will set
DTC P0112 or DTC P0113.

Linear Exhaust Gas Recirculation (EGR)
Control

The PCM monitors the exhaust gas recirculation (EGR)
actual position and adjusts the pintle position accordingly.
The PCM uses information from the following sensors to
control the pintle position:

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

Mass air flow (MAF) sensor.

Mass Air Flow (MAF) Sensor

The mass air flow (MAF) sensor measures the difference
between the volume and the quantity of air that enters the
engine. “Volume” means the size of the space to be filled.
“Quantity” means the number of air molecules that will fit
into the space. This information is important to the PCM
because heavier, denser air will hold more fuel than
lighter, thinner air. The PCM adjusts the air/fuel ratio as
needed depending on the MAF value. The Tech 2 reads
the MAF value and displays it in terms of grams per
second (gm/s). At idle, the Tech 2 should read between
4-7 gm/s on a fully warmed up engine. Values should
change quickly on acceleration. Values should remain
stable at any given RPM. A failure in the MAF sensor or
circuit will set DTC P0101, DTC P0102, or DTC P0103.

0007

Manifold Absolute Pressure (MAP) Sensor

The manifold absolute pressure (MAP) sensor responds
to changes in intake manifold pressure (vacuum). The
MAP sensor signal voltage to the PCM varies from below
2 volts at idle (high vacuum) to above 4 volts with the
ignition ON, engine not running or at wide-open throttle
(low vacuum).
The MAP sensor is used to determine the following:

Manifold pressure changes while the linear EGR flow
test diagnostic is being run. Refer to

DTC P0401.

Barometric pressure (BARO).

If the PCM detects a voltage that is lower than the
possible range of the MAP sensor, DTC P0107 will be set.
A signal voltage higher than the possible range of the
sensor will set DTC P0108. An intermittent low or high
voltage will set DTC P1107, respectively. The PCM can
detect a shifted MAP sensor. The PCM compares the
MAP sensor signal to a calculated MAP based on throttle
position and various engine load factors. If the PCM
detects a MAP signal that varies excessively above or
below the calculated value, DTC P0106 will set.

055RW004

6E2–569

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Powertrain Control Module (PCM)

The powertrain control module (PCM) is located in the
passenger compartment below the center console. The
PCM controls the following:

Fuel metering system.

Transmission shifting (automatic transmission only).

Ignition timing.

On-board diagnostics for powertrain functions.

The PCM constantly observes the information from
various sensors. The PCM 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 MIL
(Check Engine lamp), and store diagnostic trouble codes
(DTCs). DTCs identify the problem areas to aid the
technician in making repairs.

PCM Function

The PCM supplies either 5 or 12 volts to power various
sensors or switches. The power is supplied through
resistances in the PCM which are so high in value that a
test light will not light when connected to the circuit. In
some cases, even an ordinary shop voltmeter will not give
an accurate reading because its resistance is too low.
Therefore, a digital voltmeter with at least 10 megohms
input impedance is required to ensure accurate voltage
readings. Tool J 39200 meets this requirement. The PCM
controls output circuits such as the injectors, fan relays,
etc., by controlling the ground or the power feed circuit
through transistors or through either of the following two
devices:

Output Driver Module (ODM)

Quad Driver Module (QDM)

060RY00068

PCM Components

The PCM is designed to maintain exhaust emission levels
to government mandated standards while providing
excellent driveability and fuel efficiency. The PCM
monitors numerous engine and vehicle functions via
electronic sensors such as the throttle position (TP)

sensor, heated oxygen sensor (HO2S), and vehicle
speed sensor (VSS). The PCM also controls certain
engine operations through the following:

Fuel injector control

Ignition control module

ION sensing module

Automatic transmission shift functions

Cruise control

Evaporative emission (EVAP) purge

A/C clutch control

PCM Voltage Description

The PCM supplies a buffered voltage to various switches
and sensors. It can do this because resistance in the
PCM is so high in value that a test light may not illuminate
when connected to the circuit. An ordinary shop
voltmeter may not give an accurate reading because the
voltmeter input impedance is too low. Use a 10-megohm
input impedance digital voltmeter (such as J 39200) to
assure accurate voltage readings.
The input/output devices in the PCM include
analog-to-digital converters, signal buffers, counters,
and special drivers. The PCM controls most components
with electronic switches which complete a ground circuit
when turned “ON.” These switches are arranged in
groups of 4 and 7, called either a surface-mounted quad
driver module (QDM), which can independently control up
to 4 output terminals, or QDMs which can independently
control up to 7 outputs. Not all outputs are always used.

PCM Input/Outputs

Inputs – Operating Conditions Read

Air Conditioning “ON” or “OFF”

Engine Coolant Temperature

Crankshaft Position

Exhaust Oxygen Content

Electronic Ignition

Manifold Absolute Pressure

Battery Voltage

Throttle Position

Vehicle Speed

Fuel Pump Voltage

Power Steering Pressure

Intake Air Temperature

Mass Air Flow

Engine Knock

Acceleration Position

Outputs – Systems Controlled

EVAP Canister Purge

Exhaust Gas Recirculation (EGR)

Ignition Control

Fuel Control

ION Sensing Module

Electric Fuel Pump

Air Conditioning

6E2–570

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostics
– Malfunction Indicator Lamp
– Data Link Connector (DLC)
– Data Output

Transmission Control Module

PCM Service Precautions

The PCM is designed to withstand normal current draws
associated with vehicle operation. Avoid overloading any
circuit. When testing for opens and shorts, do not ground
or apply voltage to any of the PCM’s circuits unless
instructed to do so. These circuits should only be tested
using digital voltmeter J 39200. The PCM should remain
connected to the PCM or to a recommended breakout
box.

Reprogramming The PCM

Reprogramming of the PCM is done without removing it
from the vehicle . This provides a flexible and
cost-effective method of making changes in software
calibrations.
Refer to the latest Techline information on
reprogramming or flashing procedures.

Throttle Position (TP) Sensor

The throttle position (TP) sensor is a potentiometer
connected to the throttle shaft on the throttle body. The
PCM monitors the voltage on the signal line and
calculates throttle position. As the throttle valve angle is
changed (accelerator pedal moved), the TP sensor signal
also changes. At a closed throttle position, the output of
the TP1 sensor is low. As the throttle valve opens, the
output increases so that at wide open throttle (WOT), the
output voltage should be above 92% (Tech 2 Display).
The PCM calculates fuel delivery based on throttle valve
angle (driver demand). A broken or loose TP sensor may
cause intermittent bursts of fuel from an injector and
unstable idle because the PCM thinks the throttle is
moving.

060RY00027

Transmission Fluid Temperature (TFT)
Sensor

The transmission fluid temperature sensor is a thermistor
which changes its resistance based on the temperature of
the transmission fluid. For a complete description of the
TFT sensor, refer to

4L30-E Automatic Transmission

Diagnosis section.
A failure in the TFT sensor or associated wiring will cause
DTC P0712 or DTC P0713 to set. In this case, engine
coolant temperature will be substituted for the TFT
sensor value and the transmission will operate normally.

Transmission Range Switch (Mode Switch)

IMPORTANT:

The vehicle should not be driven with the

transmission range switch disconnected; idle quality will
be affected.
The four inputs from the transmission range switch
indicate to the PCM which position is selected by the
transmission selector lever. This information is used for
ignition timing, EVAP canister purge, EGR operation.
For more information on the transmission on the
transmission range switch, refer to

4L30-E Automatic

Transmission section.

Vehicle Speed Sensor (VSS)

The PCM determines the speed of the vehicle by
converting a pulsing voltage signal from the vehicle speed
sensor (VSS) into miles per hour. The PCM uses this
signal to operate the cruise control, speedometer, and the
TCC and shift solenoids in the transmission. For more
information on the TCC and shift solenoids, refer to
4L30-E Automatic Transmission section.

0008

Use of Circuit Testing Tools

Do not use a test light to diagnose the powertrain
electrical systems unless specifically instructed by the
diagnostic procedures. Use Connector Test Adapter Kit J
35616 whenever diagnostic procedures call for probing
connectors.

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