Isuzu Rodeo UE. Service manual — part 434

6E2–491

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

General Description
(PCM and Sensors)

58X Reference PCM Input

The powertrain control module (PCM) uses this signal
from the crankshaft position (CKP) sensor to calculate
engine RPM and crankshaft position at all engine speeds.
The PCM also uses the pulses on this circuit to initiate
injector pulses. If the PCM receives no pulses on this
circuit, DTC P0337 will set. The engine will not start and
run without using the 58X reference signal.

A/C Request Signal

This signal tells the PCM when the A/C mode is selected
at the A/C control head. The PCM uses this to adjust the
idle speed before turning “ON” the A/C clutch. The A/C
compressor will be inoperative if this signal is not
available to the PCM.
Refer to

A/C Clutch Circuit Diagnosis for A/C wiring

diagrams and diagnosis for the A/C electrical system.

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal
used by the powertrain control module (PCM) to calculate
the ignition sequence. The CKP sensor initiates the 58X
reference pulses which the PCM uses to calculate RPM
and crankshaft position.
Refer to

Electronic Ignition System for additional

information.

0013

Camshaft Position (CMP) Sensor and
Signal

The camshaft position (CMP) sensor sends a CMP signal
to the PCM. The PCM uses this signal as a “syncpulse” to
trigger the injectors in the proper sequence. The PCM

uses the CMP signal to indicate the position of the #1
piston during its power stroke. This allows the PCM to
calculate true sequential fuel injection (SFI) mode of
operation. If the PCM detects an incorrect CMP signal
while the engine is running, DTC P0341 will set. If the
CMP signal is lost while the engine is running, the fuel
injection system will shift to a calculated sequential fuel
injection mode based on the last fuel injection pulse, and
the engine will continue to run. As long as the fault is
present, the engine can be restarted. It will run in the
calculated sequential mode with a 1-in-6 chance of the
injector sequence being correct.
Refer to

DTC P0341 for further information.

0014

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream. Low
coolant temperature produces a high resistance of
100,000 ohms at –40

°

C (–40

°

F). High temperature

causes a low resistance of 70 ohms at 130

°

C (266

°

F).

The PCM supplies a 5-volt signal to the ECT sensor
through resistors in the PCM and measures the voltage.
The signal voltage will be high when the engine is cold and
low when the engine is hot. By measuring the voltage, the
PCM calculates the engine coolant temperature. Engine
coolant temperature affects most of the systems that the
PCM controls.
The Tech 2 displays engine coolant temperature in
degrees. After engine start-up, the temperature should
rise steadily to about 85

°

C (185

°

F). It then stabilizes

when the thermostat opens. If the engine has not been
run for several hours (overnight), the engine coolant
temperature and intake air temperature displays should
be close to each other. A hard fault in the engine coolant

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RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

sensor circuit will set DTC P0177 or DTC P0118. An
intermittent fault will set a DTC P1114 or P1115.

0016

Electrically Erasable Programmable Read
Only Memory (EEPROM)

The electrically erasable programmable read only
memory (EEPROM) is a permanent memory chip that is
physically soldered within the PCM. The EEPROM
contains the program and the calibration information that
the PCM needs to control powertrain operation.
Unlike the PROM used in past applications, the EEPROM
is not replaceable. If the PCM is replaced, the new PCM
will need to be programmed. Equipment containing the
correct program and calibration for the vehicle is required
to program the PCM.

Fuel Control Heated Oxygen Sensors

The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are mounted in the exhaust stream
where they can monitor the oxygen content of the exhaust
gas. The oxygen present in the exhaust gas reacts with
the sensor to produce a voltage output. This voltage
should constantly fluctuate from approximately 100 mV to
900 mV. The heated oxygen sensor voltage can be
monitored with a Tech 2. By monitoring the voltage output
of the oxygen sensor, the PCM calculates the pulse width
command for the injectors to produce the proper
combustion chamber mixture.

f

Low HO2S voltage is a lean mixture which will result in
a rich command to compensate.

f

High HO2S voltage is a rich mixture which will result in
a lean command to compensate.

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.

0012

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

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RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

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
resistance of 100,000 ohms at –40

°

C (–40

°

F). High

temperature causes low resistance of 70 ohms at 130

°

C

(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.

Knock Sensor

Insufficient gasoline octane levels may cause detonation
in some engines. Detonation is an uncontrolled explosion
(burn) in the combustion chamber. This uncontrolled
explosion results from a flame front opposite that of the
normal flame front produced by the spark plug. The
rattling sound normally associated with detonation is the
result of two or more opposing pressures (flame fronts)
colliding within the combustion chamber. Light
detonation is sometimes considered normal, but heavy
detonation could result in engine damage.
A knock sensor system is used to control detonation. This
system is designed to retard spark timing up to 20
degrees to reduce detonation in the engine. This allows
the engine to use maximum spark advance to improve
driveability and fuel economy.
The knock sensor system has two major components:

f

The knock sensor (KS) module.

f

The knock sensor.

The knock sensor, mounted in the engine block near the
cylinders, detects abnormal vibration in the engine. The
sensor produces an AC output signal of about 10
millivolts. The signal amplitude and frequency are
dependent on the amount of knock being experienced.
The signal voltage increases with the severity of the
knock. This signal voltage is input to the PCM. The PCM
then retards the ignition control (IC) spark timing based
on the KS signal being received.
The PCM determines whether knock is occurring by
comparing the signal level on the KS circuit with the
voltage level on the noise channel. The noise channel
allows the PCM to reject any false knock signal by
indicating the amount of normal engine mechanical noise
present. Normal engine noise varies depending on the
engine speed and load. If the voltage level on the KS
noise channel circuit is below the range considered
normal, DTC P0327 will set, indicating a fault in the KS
circuit or the knock sensor. If the PCM determines that an
abnormal minimum or maximum noise level is being
experienced, DTC P0325 will set.
The PCM contains a knock sensor (KS) module. The KS
module contains the circuitry which allows the PCM to
utilize the KS signal and diagnose the KS sensor and the
KS circuitry. If the KS module is missing or faulty, a
continuous knock condition will be indicated, and the
PCM will set DTC P0325.
Although it is a plug-in device, the KS module is not
replaceable. If the KS module is faulty, the entire PCM
must be replaced.

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RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

0009

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:

f

Engine coolant temperature (ECT) sensor.

f

Throttle position (TP) sensor.

f

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:

f

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

DTC P0401.

f

Engine vacuum level for other diagnostics.

f

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 or DTC P1106, 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.