Isuzu engine C22NE / 22LE / 20LE. Manual — part 80
DRIVEABILITY AND EMISSIONS 6E1-149
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 45)
O2 SENSOR TOO RICH (IF APPLICABLE)
Circuit Description
The engine control module (ECM) supplies a bias
voltage of about 450mV between the heated oxygen
sensor (HO2S) signal and low circuits. When
measured with a 10 megaohm digital voltmeter, this
may display as low as 320mV. The oxygen sensor
varies the voltage within a range of about 900mV
when the exhaust is rich, down through about 10mV
when exhaust is lean. The ECM constantly monitors
the HO2S signal during "Closed Loop" operation and
compensates for a rich or lean condition by
decreasing or increasing injector pulse width as
necessary. If the HO2S voltage remains excessively
high for an extended period of time.
This code detects a rich oxygen sensor reading.
Conditions for setting the DTC
• Engine run time is longer than 60sec.
• Engine coolant temperature is above 70°C(158°F).
• Throttle angle is greater than 5%.
• Following Diagnostic Trouble Codes are not set:
Malfunction DTC: 21, 22, 33, 24
• Closed Loop fuel integrator is not reset and closed
loop fuel enabled.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL).
• "Open Loop" fuel control will be in effect.
Conditions for Clearing the MIL/DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
6E1-150 DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check the following items:
• Fuel pressure - The system will go rich if pressure
is too high. The ECM can compensate for some
increase. However, if fuel pressure is too high, a
Diagnostic Trouble Code 45 may be set. Refer to
Fuel System Diagnosis.
• Perform "Injector Balance Test" - Refer to Fuel
System Diagnosis.
• Check the EVAP canister for fuel saturation - If full
of fuel, check canister control and hoses. Refer to
Evaporative (EVAP) Emission Control System.
• Check for a leak in the fuel pressure regulator
diaphragm by checking the vacuum line to toe
regulator for the presence of fuel.
• An intermittent TP sensor output will cause the
system to go rich due to a false indication of the
engine accelerating.
• Silicon contamination of the HO2S can also cause a
high HO2S voltage to be indicated. This condition is
indicated by a powdery white deposit on the portion
of the HO2S exposed to the exhaust stream. If
contamination is noticed, replace the affected
HO2S.
• Operate the vehicle while monitoring the HO2S
voltage with a Scan Tool. If the HO2S voltage is
limited within a range between 300mV to 600mV,
check the HO2S high and low circuit wiring and
associated terminal connections. If the wiring and
connections are OK, replace the HO2S.
DTC (Flash DTC = 45)
O2 Sensor Too Rich
Step
Action
Value(s)
Yes
No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
-
Go to Step 2
Go to OBD
System
Check
2
1. Install the Scan Tool.
2. Run the engine at operating temperature.
3. Operate the vehicle within parameters specified under
"Conditions for Setting the Diagnostic Trouble Code".
4. Using a Scan Tool, monitor HO2S voltage.
Does the HO2S voltage remain above the specified value?
952 mV
(500mV in
deceleration
fuel cutoff
mode)
Go to Step 4
Go to Step 3
3
1. Ignition ON.
2. Using a Scan Tool, monitor info for Diagnostic Trouble
Code 45.
3. Does the Scan Tool indicate Diagnostic Trouble Code
45.
-
Refer to
Diagnostic
Aids
Go to Step 4
4
1. Ignition OFF.
2. Disconnect HO2S.
3. Ignition ON.
4. At HO2S connector (ECM side) use a DVM to measure
voltages at the high and low signal terminals.
Are the voltages in the specified range?
5-14V
Go to Step 5
Go to Step 6
5
Repair short to voltage in signal circuit.
-
Verify repair
-
6
1. Ignition OFF.
2. Disconnect the ECM connector.
3. Check for damage to the ECM pins and terminals.
Was a problem found?
-
Verify repair
Go to Step 7
DRIVEABILITY AND EMISSIONS 6E1-151
DTC (Flash DTC = 45)
02 Sensor Too Rich (Cont’d)
Step
Action
Value(s)
Yes
No
7
1. Ignition ON, engine OFF.
2. Disconnect HO2S and jumper the HO2S high and low
circuits (ECM side) to ground.
3. Using a Scan Tool, monitor HO2S voltage.
Is HO2S voltage below the specified value?
10mV
Go to Step 8
Go to Step 9
8
Replace HO2S.
Is the action complete?
-
Verify repair
-
9
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
6E1-152 DRIVEABILITY AND EMISSIONS
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