FE02-5353b

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D

Pre-catalytic Oxygen Sensor Harness 
Connector EO02

ECM Harness Connector EO01

(a)

Turn the ignition switch to "OFF" position.

(b)

Disconnect oxygen sensor wiring harness connector EO02.

(c)

Disconnect ECM harness connector EO01.

(d)

Test Continuity between pre-catalytic oxygen sensor wiring
harness connector EO02 terminal C and ECM harness
connector EO01 terminal No.14.

Standard Resistance: Less than 1 Ω

(e)

Connect ECM harness connector EO01.

(f)

Connect pre-catalytic oxygen sensor wiring harness
connector EO02.

Is the resistance specified value?

No

ECM control circuit malfunction

Yes

Step 5

Check ECM working 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 6

Replace ECM. Refer to 

2.2.8.8

 

Engine Control Module Replacement

.

(a)

Replace ECM.

(b)

Carry out crankshaft position sensor self learn. Refer to

2.12.7.11

 

Crankshaft Position Sensor (CKP) Learn

.

Next

Step 7

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 5 min.

(f)

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

Engine

Control System JL4G15-D

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No

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

Yes

Step 8

Diagnostic completed.

5. Repair Instructions:

Replace the pre-catalytic oxygen sensor. Refer to 

2.4.7.2

 

Pre-Catalytic Oxygen Sensor Replacement

.

2.12.7.24 DTC P0137 P0138 P0140

1. DTC Descriptor:

DTC

P0137

Post-Catalytic Oxygen Sensor Circuit Short To Low Voltage

DTC

P0138

Post-Catalytic Oxygen Sensor Circuit Short To High Voltage

DTC

P0140

Post-Catalytic Oxygen Sensor Circuit Open

After the vehicle started, ECM works in open-loop mode, in which ECM ignores the Pre-Catalytic oxygen sensor signal voltage when
calculating the Air-Fuel ratio. ECM provides an approximate 450 mV reference voltage to the Pre-Catalytic oxygen sensor. When
the engine is running, Pre-Catalytic oxygen sensors start heating and begin to generate a 0-0.1 V voltage, which fluctuates. Once
ECM detects that the Pre-Catalytic oxygen sensor voltage exceeds a preset threshold voltage, ECM immediately enters into the
closed-loop mode. ECM uses Pre-Catalytic oxygen sensor signal voltage to determine the Air-Fuel ratio. If the Pre-Catalytic oxygen
sensor voltage is increased to above the reference voltage (tend to 1 V), the mixture is too rich. If the Pre-Catalytic oxygen sensor
the voltage decreased to below the reference voltage (tend to 0 mV), the mixture is too lean.

•

ECM provides a signal through ECM harness connector EO01 terminal No.30 to Post-Catalytic oxygen sensor wiring harness
connector EO03 terminal B.

•

ECM provides an internal low reference voltage through ECM harness connector EO01 terminal No.55 to Pre-Catalytic oxygen
sensor wiring harness connector EO03 terminal No.A.

2. Conditions For Setting DTC and The Fault Location:

DTC Code DTC Detection Strategy Conditions For Setting The DTC (Control Strategy)

Fault Locations

P0137

Short to Ground When Cold

1. Engine running longer than 60 s.

2. Coolant temperature is less than 70 °C (158 ºF).

3. Post-Catalytic oxygen sensor signal 0.

4. Duration longer than 25 s.

1. Sensor circuit

2. Sensor

3. ECM

P0138

Post-Catalytic oxygen
sensor voltage signal too
high

1. Engine running longer than 60 s.

2. Coolant temperature is less than 70 °C (158 ºF).

3. Post-Catalytic oxygen sensor signal around 3,200

mV.

4. Duration longer than 25 s.

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Control System JL4G15-D

Engine

DTC Code DTC Detection Strategy Conditions For Setting The DTC (Control Strategy)

Fault Locations

P0140

1. Oxygen sensor signal

circuit open

2. Oxygen sensor high-

temperature and high
resistance

1. Engine running longer than 60 s.

2. Coolant temperature is less than 70 °C (158 ºF).

3. Post-Catalytic oxygen sensor signal exceeds a

reasonable range.

4. Duration longer than 25 s.

3. Schematic

12

D

C

A

B

Main Relay

From Battery

Post-catalytic Oxygen Sensor

Engine 

Control 

Module

FE02-5206b

4. Diagnostic Steps:

Step 1

Connect scan tool.

Next

Step 2

Start engine and turn on the scan tool.

Next

Step 3

Select on the scan tool: Engine / read data flow / group 1 oxygen sensor voltage 2(Post-Catalytic oxygen
sensors).

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Control System JL4G15-D

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Next

Step 4

Observe oxygen sensor output voltage, which should be within 0.6-0.7 V.

Yes

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

No

Step 5

Carry out the oxygen sensor signal test.

(a)

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

•

Spray proper amount propane gas into intake.

•

Observe whether the Post-Catalytic oxygen sensor
voltage has a significant change, as the signal voltage will
increase rapidly.

(b)

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

•

Put the gear into neutral.

•

Apply hand brake.

•

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

•

Repeat the previous step more than 3 times.

•

Observe whether the Post-Catalytic oxygen sensor
voltage has a significant change, as the signal voltage will
decrease rapidly.

During the above test, the oxygen sensor signal voltage should
have a significant change.

Does the voltage have a significant change?

Yes

Check the cause for Air-Fuel ratio too thin /
too rich. Refer to 

2.12.7.4

 

Symptoms Table

.

No

Step 6

Confirm no other control system DTC code.

(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.

Results:

DTC Codes Shown

To Step

DTC codes other than P0137, P0138, P0140

No

P0137, P0138, P0140

Yes

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Engine