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5

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4

2

9

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51

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31

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15

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ECM Harness Connector EN01

1

2

3

Camshaft Position Sensor Harness Connector EN15

FE02-5091b

(a)

Turn the ignition switch to "OFF" position.

(b)

Disconnect camshaft position sensor wiring harness
connector EN15.

(c)

Disconnect ECM harness connector EN01.

(d)

Measure resistance between camshaft position sensor wiring
harness connector EN15 terminal No.1 and ECM harness
connector EN01 terminal No.39. Check whether the circuit is
open.

(e)

Measure voltage between camshaft position sensor wiring
harness connector EN15 terminal No.1 and a reliable ground.
Check whether the circuit is short to power supply.

Test Items

Standard Value

Resistance Between EN15 (1) and EN01 (39)

Less than 1 Ω

Voltage Between EN15 (1) and a Reliable
Ground

0 V

Execute next step as per normal.

Next

Step 9

Check whether camshaft signal plate is normal.

No

Repair the faulty part. Go to step 12

Yes

Step 10

Check ECM power supply circuit.

(a)

Check whether ECM power supply circuit is normal.

(b)

Check whether ECM ground circuit is normal.

No

Repair the faulty part.

Yes

Step 11

Replace ECM.

Next

Step 12

Use scan tool to confirm whether the DTC code is stored again.

(a)

Connect scan tool to the datalink connector.

(b)

Turn the ignition switch to "ON" position.

(c)

Clear DTC code.

(d)

Start and run the engine at idle speed to warm up the engine
for at least 5 min.

(e)

Read control system DTC code again to confirm that the
system has no DTC code.

Engine

Control System JL4G18-D

2-167

No

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

Yes

Step 13

Diagnostic completed.

5. Repair Instructions:

Replace the CMP sensor. Refer to 

2.10.8.1

 

Camshaft Position Sensor Replacement

.

2.2.7.32 DTC P0420

1. DTC Descriptor:

DTC

P0420

Three-way Catalytic Converter Oxygen Storage Capacity Aging (Emission Over the Limit)

ECM uses two oxygen sensors (Pre-Catalytic oxygen sensor and Post-Catalytic oxygen sensor) installed before and after the three-
way catalytic converters to monitor the conversion efficiency of the three-way catalytic converter (TWC). ECM uses Pre-Catalytic
oxygen sensor for Air-Fuel ratio close-loop control and monitors oxygen content in the exhaust gas not purified by TWC. The Post-
Catalytic oxygen sensor sends voltage signal to ECM indicating the oxygen content in the exhaust gas purified by the TWC. ECM
compares signals from the two sensors to determine whether the TWC is currently under normal working condition. If the calculated
TWC conversion efficiency is too low, the fault lamp will be lit and the DTC code will be set.

2. Conditions For Setting DTC and The Fault Location:

DTC Code

DTC Detection Strategy

Conditions For Setting The DTC

(Control Strategy)

Fault Locations

P0420

Exceed the Maximum Limit

1. After adjustment, the post-

catalytic oxygen sensor signal is
greater than the average
amplitude, which is 0.48 V.

2. Catalytic converter monitoring

activation time is greater than 70
s.

1. Pre-Catalytic Oxygen Sensor

2. Post-Catalytic Oxygen Sensor

3. Three-way Catalytic Converter

4. Exhaust Leakage

3. Schematic:

Refer to 

2.2.6.1

 

Schematic

4. Diagnostic Steps:

Note

Before carrying out this diagnosis step, observe the data list on scan tool and analyze the accuracy of the data, as
these will help with quick diagnosis.

Step 1

Check whether there are control system DTC codes other than DTC P0420.

(a)

Connect scan tool to the 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.

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Control System JL4G18-D

Engine

DTC Codes Shown

To Step

DTC P0420

Yes

DTC Code Other Than DTC P0420

No

No

Refer to 

2.2.7.11

 

DTC Code Index

Yes

Step 2

Start the engine and turn on the scan tool.

Next

Step 3

Keep the 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 the scan tool: Engine/Read data/Group 1 oxygen sensor voltage 1 (Pre-Catalytic oxygen sensor),
Group 1 oxygen sensor voltage 2 (Post-Catalytic oxygen sensor)

Next

FE02-5092b

0V

0V

0V

0V

1V

1V

1V

1V

Deteriorated TWC

Normal TWC

Pre-catalytic 

Oxygen Sensor

Post-catalytic 

Oxygen Sensor

Engine

Control System JL4G18-D

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Step 5

Observe Pre-Catalytic oxygen sensor and Post-Catalytic oxygen sensor output voltages.

Whether Pre-Catalytic oxygen sensor and Post-Catalytic oxygen
sensor signal voltage is matching "Normal TWC" in the figure?

Yes

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

No

Warning!

Propane gas is a flammable gas. It is strictly prohibited to operate propane gas near a fire, otherwise it will cause a
fire.

Step 6

Test the oxygen sensor signal.

(a)

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

•

Spray proper amount of propane gas into the intake.

•

Inspect whether the sensor voltage data changes
significantly, as the signal voltage will increase rapidly.

Pre-Catalytic Oxygen

Sensor Signal Voltage

Post-Catalytic Oxygen
Sensor Signal Voltage

To Step

Obvious Change

No Change

A

No Change

Obvious Change

B

Obvious Change

No Change

C

No Change

No Change

D

B

Replace the pre-catalytic oxygen sensor.
Refer to 

2.4.7.2

 

Pre-Catalytic Oxygen Sensor

Replacement

. Go to step 11

C

Go to step 9

D

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

2.2.7.4

 

Fault Symptom

Table

A

Step 7

Check whether there is exhaust leakage.

Yes

Repair the faulty part. Go to step 11

No

Step 8

Replace the three-way catalytic converter. Refer to 

2.7.6.2

 

Three-way Catalytic Converter Replacement

.

Next

Go to step 11

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