FE02-5046 b

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Pre-catalytic Oxygen Sensor 

Harness Connector EN02

ECM Harness Connector EN01

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(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 the oxygen sensor wiring
harness connector EN02 terminal No.3 and ECM harness
connector terminal No.39. 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.3 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.3 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 (3) and EN01 (39)

Less than 1 Ω

Resistance Between EN02 (3) and a Reliable
Ground

10 kΩ or higher

Voltage Between EN02 (3) and a Reliable
Ground

0 V

Execute next step as per normal.

Next

Step 13

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 14

Replace ECM.

Next

Step 15

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)

Road test the vehicle for at least 10 min.

(f)

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

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Control System JL4G18-D

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No

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

Yes

Step 16

Diagnostic completed.

5. Repair Instructions:

Replace the pre-catalytic oxygen sensor. Refer to 

2.4.7.2

 

Pre-Catalytic Oxygen Sensor Replacement

.

2.2.7.22 DTC P0136 P0137 P0138 P0140 P2270 P2271

1. DTC Descriptor:

DTC

P0136

Post-Catalytic Oxygen Sensor Unreasonable

DTC

P0137

Post-Catalytic Oxygen Sensor Circuit Voltage Too Low

DTC

P0138

Post-Catalytic Oxygen Sensor Circuit Voltage Too High

DTC

P0140

Post-Catalytic Oxygen Sensor Circuit Malfunction

DTC

P2270

Post-Catalytic Oxygen Sensor Aging (Tool Lean)

DTC

P2271

Post-Catalytic Oxygen Sensor Aging (Too Rich)

After the vehicle is started, the control module works in the open-loop mode and ignores heated oxygen sensor signal voltage when
calculating air-fuel ratio. The control module provides approximately 450mV reference voltage to the heated oxygen sensor. When
the engine starts running, the heated oxygen sensor will be heated and begin to generate a 0-0.1V voltage. This voltage fluctuates.
Once the control module detects that the heated oxygen sensor voltage exceeds a threshold voltage, it will immediately enter into
the closed-loop mode. Control module determines the air-fuel ratio using the received heated oxygen sensor voltage signal. If the
heated oxygen sensor voltage increases to over the reference voltage (tend to 1V), it indicates that the air fuel mixture is too rich.
If the heated oxygen sensor voltage decreases to below the reference voltage (tend to 0mV), it indicates that the air fuel mixture is
too lean.

•

ECM provides a signal through ECM harness connector EN01 terminal No.29 to post-catalytic oxygen sensor wiring harness
connector EN03 terminal No.4.

•

ECM provides a low reference voltage through ECM harness connector EN01 terminal No.39 to pre-catalytic oxygen sensor
wiring harness connector EN03 terminal No.3.

2. Conditions For Setting DTC and The Fault Location:

DTC Code

DTC Detection Strategy

Conditions For Setting The DTC

(Control Strategy)

Fault Locations

P0136
P0137

Short to Ground When Cold

1. Post-Catalytic oxygen sensor

voltage is less than 0.06 V.

2. Post-Catalytic oxygen sensor

reaches the normal working
temperature.

1. Sensor Circuit

2. Sensor

3. Mixture Too Rich

4. Mixture Too Lean

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Control System JL4G18-D

Engine

DTC Code

DTC Detection Strategy

Conditions For Setting The DTC

(Control Strategy)

Fault Locations

P0138

5. Three-way Catalytic

Converter

6. ECM

Post-Catalytic Oxygen Sensor
Voltage Too High

1. Post-Catalytic oxygen voltage

signal is greater than 1.5 V.

2. Battery voltage is greater than

10.98 V.

3. Engine speed is greater than 25

rpm.

4. Target excess air coefficient is

equal to 1.

5. Three-way catalytic converter

temperature is higher than 320°C
(608 ºF).

6. Battery voltage is greater than

10.98 V.

7. Post-Catalytic oxygen sensor

reaches the normal working
temperature.

P0140

1. Oxygen Sensor Signal Circuit

Open

2. Oxygen Sensor With High

Resistance at High Temperature

1. Post-Catalytic oxygen sensor

voltage is between 0.42 V and 0.5
V.

2. Post-Catalytic oxygen sensor

resistance is greater than 40,000
Ω.

3. Post-Catalytic oxygen sensor

reaches the normal working
temperature.

1. Sensor Circuit

2. Sensor

3. Mixture Too Rich

4. Mixture Too Lean

5. Three-way Catalytic

Converter

6. ECM

P2270
P2271

1. Post-Catalytic oxygen sensor

voltage is continuously low.

2. Post-Catalytic oxygen sensor

voltage is continuously high.

1. Post-Catalytic oxygen sensor

voltage is less than 0.6 V.

2. Post-Catalytic oxygen sensor

voltage is greater than 0.6 V.

3. Post-Catalytic oxygen sensor

reaches the normal working
temperature.

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3. Schematic

12

14

Main Relay

From Battery

Engine 

Control 

Module

From Pre-catalytic Oxygen Sensor

Post-catalytic Oxygen Sensor

FE02-5012b

4. Diagnostic Steps:

Step 1

Connect scan tool.

Next

Step 2

Start engine and turn on the scan tool.

Next

Step 3

Maintain 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  scan  tool:  Engine/Read  data  flow/Group  1  Oxygen  sensor  voltage  2  (Post-Catalytic  oxygen
sensors).

Next

Step 5

Observe oxygen sensor output voltage, the data should be within 0.6-0.7V unchanged.

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Control System JL4G18-D

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