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2002 Isuzu Trooper LS PCM Senosr Codes

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

• An example of charging by friction is a person sliding across a vehicle seat.
• Charge by induction occurs when a person with well insulated shoes stands near a highly charged object and momentary touches ground. Charges of the same polarity are drained off leaving the person highly charged with the opposite polarity. Static charges can cause damage, therefore it
  is important to use care when handling and testing electronic components.
NOTE: To prevent possible electrostatic discharge damage, follow these guidelines:
• Do not touch the PCM connector pins or soldered components on the PCM circuit board.
• Do not touch the knock sensor module component leads
• Do not open the replacement part package until the part is ready to be installed.
• Before removing the part from the package, ground the package to a known good ground on the vehicle.
• If the part has been handled while sliding across the seat, while sitting down from a standing position, or while walking a distance, touch a know
  good ground before installing the part.

• The amount of fuel delivered.
• The idle RPM.
• Ignition dwell time.

• The fuel injectors
• The throttle body
• The fuel rail.
• The fuel pressure regulator.
• The PCM
• The crankshaft position (CKP) sensor.
• The camshaft position (CMP) sensor
• The idle air control (IAC) valve.
• The fuel pump.
• The fuel pump relay.

• Open loop
• Closed loop

When the engine is first started the system is in 'open loop" operation. In "open loop," the PCM ignores the signal from the heat oxygen sensor (H02S)l.
It calculates the air/fuel ratio based on inputs from the TP, ECT, and MAF sensors.
The system remains in "open loop" until the following conditions are met:

• The H02S has a varying voltage output showing that it is hot enough to operate properly (this depends on temperature).
• The ECT has reached a specified temperature.
• A specific amount of time has elapsed since starting the engine.
• Engine speed has been greater than a specified RPM since start-up.

The specific values for the above conditions vary with different engines and are stored in the programmable read only memory (PROM). When these
conditions are met, the system enters "closed loop" operation. In "closed loop" the PCM calculates the air/fuel ratio (injector on-time) based on the
signal from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1.

Starting Mode
when the ignition is first turned "ON, " the PCM energizes the fuel pump relay for two seconds to allow the fuel pump to build up pressure.
The PCM then checks the engine coolant temperature (ECT) sensor and the throttle position (TP) sensor to determine the proper air/fuel ratio for starting.
The PCM controls the amount of fuel delivered in the starting mode by adjusting how long the fuel injectors are energized by pulsing the injector for very short times.
Throttle Body Unit
Has a throttle plate to control the amount of air delivered to the engine. The TP sensor and IAC valve are also mounted on the throttle body.
Vacuum ports located behind thee throttle plate provide the vacuum signals needed by various components.
Engine coolant is directed through a coolant cavity in the throttle body to warm the throttle valve and to prevent icing.

General Description (Electronic Ignition System)
Camshaft Position (CMP) Sensor
As the camshaft sprocket turns, a magnet in the sprocket activates the Hall-effect switch in the CMP sensor. When the Hall-effect switch is activated,
it grounds the signal line to the PCM, pulling the camshaft position sensor signal circuit's applied voltage low. This is a CMP singal. The CMP signals is
created as piston #1 is approximately 25° after top dead counter on the power stroke. If the correct CMP signal is not received by the PCM, DTC PO341
will be set.

Crankshaft Position (CKP) Sensor
Provides a signal used by the powertrain control module (PCM) to calculate the ignition sequence. The sensor initiates the 58X reference pulses which
the PCM uses to calculate RPM and crankshaft position.
Electronic Ignition
This system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide optimum engine
performance, fuel economy, and control of exhaust emissions, the PCM controls the spark advance of the ignition system. Electronic ignition has the
following advantages over a mechanical distributor system:

• No moving parts.
• Loss maintenance.
• Remote mounting Capability.
• No mechanical load on the engine.
• More coil cool-down time between firing events.
• Elimination of mechanical timing adjustments.
• Increased available ignition coil saturation time.

Ignition Coils
A separate coil-at-plug module is located at each spark plug. The coil-at-plug module is attached to the engine with two screws. It is installed directly to
the spark plug by an electrical contact inside a rubber boot. A three-way connector provides 12-volt primary supply from the 15-amp ignition fuse, a
ground-switching trigger line from the PCM, and a ground.

Ignition Control
The ignition control (IC) spark timing is the PCM's method of controlling the spark advance and the ignition dwell.

The IC spark advance and the ignition dwell are calculated by the PCM using the following inputs:

• Engine speed
• Crankshaft position (58X reference).
• Camshaft position (CMP) sensor
• Throttle position (TP) sensor
• Knock signal (knock sensor).
• Park/Neutral position (PRNDL input).
• Vehicle speed (vehicle speed sensor).
• PCM and ignition system supply voltage.
• The crankshaft positron (CKP) sensor sends the PCM a 58X signal related to the exact position of the crankshaft.
• The camshaft position (CMP) sensor sends a signal related to the position of the camshaft.
• The Knock sensor tells the PCM if there is any problem with pre-ignition or detonation. This information allows the PCM to retard timing, if necessary

Based on these sensor signals and engine load information, the PCM sends 5 Volts to each ignition coil.

The PCM applies 5 volts signal voltage to the ignition coil requiring ignition. This signal sets on the power transistor of the ignition coil to establish a
grounding circuit for the primary coil, apply battery voltage to the primary coil.
At the ignition timing, the PCM stops sending the 5V signal voltage. Under this condition the power transistor of the ignition coil is set off to cut the
battery voltage to the primary coil, thereby causing a magnetic field generated in the primary coil to collapse, On this moment a line of magnetic force
flows to the secondary coil, and when this magnetic line crosses the coil, high voltage induced by the secondary ignition circuit to flow through the spark
plug t the ground.
Ignition Control PCM Output

6E-347

Intake Air Temperature (IAT) Sensor
The air temperature sensor is a thermostat 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 cause 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.

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 under-hood temperature increases. If the engine has 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 P112 or DTC P0113.

Electrically Erasable Programmable Read Only Memory
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 PC 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
Bank 1 HO2S 1 and (Bank 2 HO2S 1) are mounted on the exhaust steam 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
100MV to 900 mV. The heated oxygen sensor voltage can be monitored with Tech f2. 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.

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

Intake Air Temperature (IAT) Sensor
The air temperature sensor is a thermostat 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 cause 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.

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 under-hood temperature increases. If the engine has 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 P112 or DTC P0113.

Knock Sensor
Insufficient gasoline octane levels may cause detonation is 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 drivability and fuel economy.

• The knock sensor system has two major components:
• The knock sensor (KS) module
The knock sensor, mounted in the engine block near the cylinder, detects abnormal vibration in the engine. The sensor produces an AC output signal of
about 10 milli-volts. 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 in not replaceable. If the KS module is faulty, the entire PCM must be replaced.

Linear Exhaust Gas Recalculation (EGR) Control
The PCM monitors the exhaust gas recalculation (EGR) actual position and adjusts the pintle, (pintle: One of the pins (on the forward edge of a rudder)
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) Senor
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. Tech 2 reads
the MAF value and displays it in terms of grams per second (gm/s). At idle, 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.
MASS AIR FLOW SENSOR Parts warehouse $52.99
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 a 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.
• Engine vacuum level for other diagnostics
• Barometric pressure (BBRO)



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 that 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

Powertrain Control Module (PCM
This sensor is located in the passenger compartment below the center console. The PCM controls the following:

• Fuel metering system
• Transmission shifting (automatic transmission only)
• On-board diagnostics for powertrain functions
• Ignition timing

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 (Service Engine soon Lamp), and store
diagnostic trouble codes (DTCs). DTCs identify the problem areas to aid the technician in making repairs.
This engine uses 2 different control modules

• IPCM-69KT for automatic Transmission-equipped vehicles
• ISFI-6for manual Transmissions-equipped vehicles

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 cased, 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 meg-ohms input impedance is required to ensure accurate voltage readings. Tool J39200 meets this
requirement. The PCM controls output circuits such as the injectors, IAC, cooling fan relays, etc., by controlling the ground or the power feed circuit
through transistors of following device.

• Output Driver Module (ODM)

PCM Components
The PCM is designed to maintain exhaust emission levels to government mandated standards while providing excellent drivability 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
• Knock sensor
• Automatic transmission shift functions
• Cruise control
• 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 many not give an accurate reading because the voltmeter input impedance is
too low. Use a 10-meg-ohm 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 component
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
• Camshaft Position

Outputs-Systems Controlled

• Exhaust Gas Recalculation (EGR)
• Ignition Control
• Fuel Control
• Idle Air Control
• Electric Fuel Pump
• Air Conditioning
• Diagnostic
--Malfunction Indicator Lamp (Service Engine Soon Lamp)
--Data Link Connector (DLC)
--Data Output

• Transmission Control Module
• Alternator Gain Control

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 Tech-2.
The PCM should remain connected to the PCM or to a recommended breakout box.

Reprogramming the PCM
The Trooper allows reprogramming of the PCM without removing it from the vehicle. This provides a flexible and cost-effective method of making
changes I software calibrations.
The service programming system (SPS) will not allow incorrect software programming or incorrect calibration changes.

Throttle Position (TP) Sensor
The throttle position 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 TP sensor is low. As the throttle valve opens, the output increases so that a wide open throttle (WOT), the output voltage
should be about 4 volts.
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. A hard failure in the TP sensor 5-volt reference or signal circuits will set a
DTC P0123. A hard failure with the TP sensor ground circuit may set DTC P0123. Once a DTC is set, the PCM will use an artificial default value based on
engine RPM and mass air flow for the throttle position, and some vehicle performance will return. A high idle may result when DTC P0123 is set.
The PCM can also detect a shifted TP sensor. The PCM monitors throttle position and compares the actual TP sensor reading to a predicted TP value
calculated from engine speed. If the PCM detects an out-or-range condition, DTC P0121 will be set

Transmission Fluid Temperature (TFT) Sensor
The transmission fluid temperature sensor is a thermostat which changes its resistance based on the temperature of the transmission fluid.
A failure in the TFT sensor or associated wiring will cause DTC P0712 or DTC P0723 to set. In this case, engine coolant temperature will be substituted
for the TFT sensor value and the transmission will operate normally.

Circuit Description
The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission fluid pressure (TFP) manual valve position switch.
The TFT sensor is a resistor, or thermostat, which changes value based on temperature. The sensor has a negative-temperature coefficient. This means
that as the temperature increases, the resistance decreases, and as the temperature decreases, the resistance increases. The powertrain control module
(PCM) supplies a 5-volt reference signal to the sensor on circuit 1227 and measures the voltage drop in the circuit. When the transmission fluid is cold,
the sensor resistance is high and the PCM detects high signal voltage. As the fluid temperature warms to a normal operating temperature, the resistance
becomes less and the signal voltage decreases. The PCM uses this information to control shift quality and torque converter clutch apply.
When the PCM detects a continuous short to ground in the TFT signal circuit or in the TFT sensor, then DTC P0712 sets. DTC P0712 is a type C DTC.

Transmission Range 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 and IAC vale operation