Geely Emgrand X7. Manual part — 193

2.12.7.24 DTC P0137 P0138 P0140

1. DTC

description:

DTC P0137

Rear Oxygen Sensor Circuit Short to Low Voltage

DTC P0138

Rear Oxygen Sensor Circuit Short to High Voltage

DTC P0140

Rear Oxygen Sensor Circuit Open

After the vehicle started, ECM works in open-loop mode, in which ECM ignores the heated type
oxygen sensor signal voltage when calculating the Air-Fuel ratio. The control module provides
approximately 450mV reference voltage to the heated oxygen sensor. When the engine starts
running, the heated type 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
type oxygen sensor voltage increases to above the reference voltage (tend to 1 V), the mixture is
too thick. If the heated oxygen sensor voltage decreases to below the reference voltage (tend to
0mV), it indicates that the air fuel mixture is too thin.

•

ECM provides a signal through ECM harness connector EN01 terminal No.48 to rear oxygen
sensor wiring harness connector EN03 terminal B.

•

ECM provides an internal low reference voltage through ECM harness connector EM01
terminal No.73 to front oxygen sensor wiring harness connector EM03 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 60s.

2. Water temperature is more than

70 (158 ºF)

℃

3. Rear Oxygen Sensor Short to

Ground

4. Duration Longer Than 25s.

P0138

Post-catalytic Oxygen
Sensor Voltage Too
High

1. Engine Running Longer than 60s.

2. Water temperature is more than

70 (158 ºF)

℃

3. Rear oxygen sensor signal is

terminated at the power supply.

4. Duration Longer Than 13s.

P0140

1. Oxygen Sensor 1. Engine Running Longer than 60s.

1. Sensor

Circuit

2. Sensor

3. ECM.

771

Signal Circuit
Open

2. Oxygen Sensor

With High
Resistance at High
Temperature

2. Water temperature is more than

70 (158 ºF)

℃

3. Rear oxygen sensor signal

exceeds a reasonable range.

4. Duration Longer Than 165s.

3. Circuit

sketch

NL02-2065b

BAT

15

A

E

F2

1

86

87

30

85

发动机主继电器

D

EN03

C

EN03

B

EN03

A

EN03

后氧传感器

23

EN01 O

2

BHTR

48

EN01 O

2

HI

73

EN01

44

EN01

V5RTN3

MPR

ECM

4. Diagnostic

Steps:

Step 1

Connect a fault diagnosis tester.

Step 2

Start engine and turn on the fault diagnosis tester.

Step 3

(d) Select on the fault diagnosis tester: Engine / Read Data Flow / Group 1 Oxygen
Sensor Voltage 2 (Rear Oxygen Sensor).

Step 4

Observe oxygen sensor output voltage, the data should be within 0.16-0.7V
unchanged.

Next

Next

Next

Engine
main relay

Rear oxygen sensor

772

Step 5

Carry out the oxygen sensor signal test.

(a) If the voltage data is consistently lower than 0.45 V (mixture too thin), carry out the

following inspection steps:

z Spray proper amount of propane gas into the intake.

z Check whether the rear oxygen sensor voltage data has a significant change, as it will cause

signal voltage to rise rapidly.

(b) If the voltage data is consistently higher than 0.45 V (mixture too thick), carry out the

following inspection steps:

z Put the transmission gear into neutral.

z Apply hand brake.

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

quickly release the accelerator pedal.

z Repeat the previous steps more than 3 times.

z Check whether the rear oxygen sensor voltage data has a significant change, as it will cause

signal voltage to decrease rapidly.

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

Is voltage changed significantly?

(a) Connect fault diagnosis tester to the vehicle diagnostic interface.

(b) Turn ignition switch to ON position.

(c) Press the fault diagnosis tester power button.

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

(e) Read DTC codes.

DTC Codes Shown

To Step

DTC except for P0137,P0138,P0140

No

P0137、P0138、P0140 Yes

Step 6

Inspect there are no other control system DTC codes output.

Yes

Inspect the cause for engine air-fuel ratio too lean/too rich.
Refer to 2.12.7.4 Fault Symptom Table.

No

Yes

Intermittent fault refers to 2.12.7.3 List of
Intermittent Fault.

No

773

Step 7

Inspect the sealing of exhaust system.

(a) Inspect whether the three-way catalytic converter looks good (signs of excessive heat and

gasket missing, etc.).

(b) Inspect whether the exhaust pipe is intact and whether gasket is intact.

Step 8

Measure rear oxygen sensor signal circuit.

(a) Rotated ignition switch to OFF

position .

(b) Disconnect the rear oxygen

sensor harness connector EN03.

(c) Rotated ignition switch to ON

position .

(d) Measure voltage between rear

oxygen sensor wiring harness
connector EN03 terminal B and a
reliable ground.

Standard Voltage: 0.35-0.5V

(e) Connect the rear oxygen sensor

harness connector EN03.

NL02-2066b

A

B

C

D

EN03 后氧传感器线束连接器

B

Is voltage the specified value?

Step 9

Measure the rear oxygen sensor ground circuit.

No

Go to step 11

Yes

No

Replace the damaged components. Go to
step 15.

No

Refer to 2.12.7.14 DTC Chapter Index.

Yes

EN03 rear oxygen sensor harness connector

774