Electrically Erasable Programmable Read Only Memory (Eeprom); Fuel Control Heated Oxygen Sensors - Isuzu 2000 Trooper Workshop Manual

6E–564
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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.
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.
D Low HO2S voltage is a lean mixture which will result in
a rich command to compensate.
D 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.
0016
Catalyst Monitor Heated Oxygen Sensors
The EEPROM
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.
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.
incorrect catalyst monitor diagnostic results.
060RY00030
If the catalyst is operating
This may cause