3. Schematic:

12

13

From Battery

Main Relay

Pre-catalytic Oxygen Sensor

To Post-catalytic Oxygen Sensor

Engine 

Control 

Module

FE02-5008b

4. Diagnostic Steps:

Step 1

Connect scan tool.

Next

Step 2

Start engine and turn on the scan tool.

Next

Step 3

Maintain engine speed at 2,500 rpm for more than 2 min to warm up the engine, until the engine coolant
temperature reaches 80°C (176 ºF).

Next

Step 4

Select  on  scan  tool:  Engine/Read  data  stream/group  1  oxygen  sensor  voltage  1  (Pre-Catalytic  oxygen
sensors).

Next

Step 5

Observe the oxygen sensor output voltage, the data should fluctuate within 0.1-0.8 V.

Engine

Control System JL4G18-D

2-111

Yes

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

No

Step 6

Test the oxygen sensor signal.

(a)

If the voltage data is consistently below 0.45 V (mixture too
lean), then carry out inspection steps as following:

•

Spray proper amount of propane gas into the intake port.

•

Inspect whether the pre-catalytic oxygen sensor voltage
data has a significant change, in which case the signal
voltage will increase rapidly.

(b)

If the voltage data is consistently higher than 0.45 V (mixture
too rich), then carry out inspection steps as following:

•

Put gear into Neutral.

•

Apply hand brake.

•

Press the accelerator pedal so the engine speed
suddenly increases to 4,000 rpm and then quickly release
the accelerator pedal.

•

Repeat the previous steps more than 3 times.

•

Inspect whether the pre-catalytic oxygen sensor voltage
data has a significant change, in which case the signal
voltage will decrease rapidly.

During the above test, the pre-catalytic oxygen sensor signal
voltage should change significantly.

Is voltage changed significantly?

Yes

Inspect the cause for engine air-fuel ratio too
lean/too rich. Refer to 

2.2.7.4

 

Fault Symptom

Table

.

No

Step 7

Check and confirm no other control system DTC codes.

(a)

Connect scan tool to a datalink connector.

(b)

Turn the ignition switch to "ON" position.

(c)

Press the scan tool power button.

(d)

Select the following menu items: Engine/Read DTC codes.

(e)

Read DTC codes.

Results:

DTC Codes Shown

To Step

DTC codes other than P0030, P0031, P0032,
P0053

No

P0030, P0031, P0032, P0053

Yes

No

Refer to 

2.2.7.11

 

DTC Code Index

2-112

Control System JL4G18-D

Engine

Yes

Step 8

Measure pre-catalytic oxygen sensor signal circuit.

FE02-5043b

1

2

3

4

Pre-catalytic Oxygen Sensor 

Harness Connector EN02

(a)

Turn the ignition switch to "OFF" position.

(b)

Disconnect oxygen sensor wiring harness connector EN02.

(c)

Turn the ignition switch to "ON" position.

(d)

Measure voltage between Pre-Catalytic oxygen sensor
wiring harness connector EN02 terminal No.4 and a reliable
ground.

Standard Voltage: 0.35-0.5 V

(e)

Connect the pre-catalytic oxygen sensor wiring harness
connector EN02.

Is voltage the specified value?

No

Go to step 11

Yes

Step 9

Measure the pre-catalytic oxygen sensor ground circuit.

FE02-5044b

1

2

3

4

Pre-catalytic Oxygen Sensor 

Harness Connector EN02

(a)

Turn the ignition switch to "OFF" position.

(b)

Disconnect oxygen sensor wiring harness connector EN02.

(c)

Turn the ignition switch to "ON" position.

(d)

Measure resistance between pre-catalytic oxygen sensor
connector EN02 terminal No.3 and a reliable ground.

Standard Resistance: Less than 1 Ω

(e)

Connect pre-catalytic oxygen sensor wiring harness
connector EN02.

Is resistance the specified value?

No

Go to step 12

Yes

Step 10

Replace the pre-catalytic oxygen sensor. Refer to 

2.4.7.2

 

Pre-Catalytic Oxygen Sensor Replacement

.

Next

Go to step 15

Step 11

Check the pre-catalytic oxygen sensor signal circuit.

Engine

Control System JL4G18-D

2-113

FE02-5045b

1

3

5

7

8

6

4

2

9

10

11

12

13

23

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25

26

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28

29

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37

51

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36

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22

1

2

3

4

Pre-catalytic Oxygen Sensor 

Harness Connector EN02

ECM Harness Connector EN01

(a)

Turn the ignition switch to "OFF" position.

(b)

Disconnect oxygen sensor wiring harness connector EN02.

(c)

Disconnect ECM harness connector EN01.

(d)

Measure resistance between pre-catalytic oxygen sensor
wiring harness connector EN02 terminal No.4 and ECM
harness connector terminal No.45. Check whether the circuit
is open. If there is no open circuit, repair the faulty part.

(e)

Measure resistance between pre-catalytic oxygen sensor
wiring harness connector EN02 terminal No.4 and a reliable
ground. Check whether the circuit is short to ground. If there
is no short circuit, repair the faulty part.

(f)

Measure voltage between Pre-Catalytic oxygen sensor
wiring harness connector EN02 terminal No.4 and a reliable
ground. Check whether the circuit is short to power supply. If
there is no short circuit, repair the faulty part.

Test Items

Standard Value

Resistance Between EN02 (4) and EN01
(45)

Less than 1 Ω

Resistance Between EN02 (4) and a
Reliable Ground

10 kΩ or higher

Voltage Between EN02 (4) and a Reliable
Ground

0 V

Normal

Go to step 15

Step 12

Check the pre-catalytic oxygen sensor ground circuit.

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Control System JL4G18-D

Engine