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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

Was the "On-Board Diagnostic (OBD) System Check"

performed?

Go to Step 2

Go to OBD

System

Check

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

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

Check for a damaged harness.

Was a problem found?

Verify repair

Go to Step 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

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

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

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

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

Replace HO2S.

Is the action complete?

Verify repair

Replace the EPROM or ECM.

Note) Refer to 6E1-243.

Is the action complete?

Verify repair

6E1-144 DRIVEABILITY AND EMISSIONS

Content .. 76 77 78 79 ..