Isuzu engine C22NE / 22LE / 20LE. Manual — part 78
DRIVEABILITY AND EMISSIONS 6E1-141
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 13)
O2 SENSOR CIRCUIT NOT READY DETECTED (IF APPLICABLE)
Circuit Description
• The engine control module (ECM) supplies a bias
voltage of about 450mV between the heated
oxygen sensor (HO2S) high 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 60mV
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. This code determines whether the
oxygen sensor is ready for use as a feedback for
fuel control system. Then the DTC 13 will set.
Conditions for Setting the DTC
• Engine run time is longer than 60 seconds.
All the above conditions are met and the following
condition is met:
• HO2S signal voltage remains between 343mV and
540mV.
• Throttle angle is greater than 5%.
• ECT greater than 70°C.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL) the second time the fault is detected.
• "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.
6E1-142 DRIVEABILITY AND EMISSIONS
Diagnostic Aids
Check for the following conditions:
• Poor connection or damaged harness - Inspect the
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed
or damaged terminals, poor terminal-to-wire
connection, and damaged harness.
• Faulty HO2S heater or heater circuit - With the
ignition ON engine OFF after a cool down period,
the HO2S voltage displayed on the Scan Tool is
normally 455-460mV. A reading over 1000mV
indicates a signal line shorted to voltage. A reading
under 5mV indicates a signal line shorted to ground
or signal lines shorted together. Disconnect the
HO2S and connect a test light between the HO2S
battery feed and heater ground circuits. If the test
light does not light for 2 seconds when the ignition
is turned on, repair the open battery feed or sensor
ground circuit as necessary. If the test light lights
and the HO2S signal and low circuits are OK,
replace the HO2S.
• Intermittent test - With the ignition ON monitor the
HO2S signal voltage while moving the wiring
harness and related connectors. If the fault is
induced, the HO2S signal voltage will change. This
may help isolate the location of the malfunction.
DTC (Flash DTC = 13)
O2 Sensor Circuit Not Ready
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 engine above 1200 RPM for three
minutes.
Does the Scan Tool indicate HO2S voltage varying outside
the specified values?
400-500mV
Go to Step 3
Go to Step 4
3
1. Ignition ON, engine OFF.
2. Using a Scan Tool, monitor info for Diagnostic Trouble
Code 13.
3. Note the test result.
Does the Scan Tool indicate Diagnostic Trouble Code 13
failed this ignition?
-
Go to Step 4
Refer to
Diagnostic
Aids
4
Check for a damaged harness.
Was a problem found?
-
Verify repair
Go to Step 5
5
Check for poor HO2S high and low circuit terminal
connections at the HO2S harness connector and replace
terminal(s) if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 6
6
Check for poor HO2S high and low circuit terminal
connections at the ECM and replace terminals if
necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 7
DRIVEABILITY AND EMISSIONS 6E1-143
DTC (Flash DTC = 13)
O2 Sensor Circuit Not Ready (Cont'd)
Step
Action
Value(s)
Yes
No
7
1. Ignition OFF.
2. With the ECM disconnected, check continuity of the
HO2S high circuit.
3. If the HO2S high circuit measures over 0.5 ohms,
repair open or poor connection as necessary.
Was a HO2S high circuit problem found and corrected?
-
Verify repair
Go to Step 8
8
1. Ignition OFF.
2. With the ECM disconnected, check continuity of the
HO2S low circuit.
3. If the HO2S low circuit measures over 5 ohms, repair
open or poor connection as necessary.
Was a HO2S low circuit problem found and corrected?
-
Verify repair
Go to Step 9
9
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 approximately equal to the specified
value?
10mV
Go to Step 10
Go to Step 11
10
Replace HO2S.
Is the action complete?
-
Verify repair
-
11
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
Is the action complete?
-
Verify repair
-
6E1-144 DRIVEABILITY AND EMISSIONS
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