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DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2)

DTC P0138 O 2 SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2)

DTC DETECTING CONDITION:


• Two consecutive driving cycles with fault

• GENERAL DESCRIPTION


Important

After repair or replacement of faulty parts, conduct Clear Memory Mode and Inspection Mode .


WIRING DIAGRAM:


CHECK ANY OTHER DTC ON DISPLAY.

Is any other DTC displayed?

Yes

• Check DTC using “List of Diagnostic Trouble Code (DTC)”.

•
Note

In this case, it is not necessary to inspect DTC P0138.



No


CHECK REAR OXYGEN SENSOR DATA.

Warm-up the engine until engine coolant temperature is above 70°C (158°F), and immediately decrease the engine speed from 5,000 rpm.

Read the data of rear oxygen sensor signal using Vehicle Diagnostic Interface or OBD-II general scan tool.

Note
• Vehicle Diagnostic Interface

For detailed operation procedure, refer to the “READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE”.

• OBD-II general scan tool

For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.


Is the voltage 250 mV?

Yes


No


CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.

Turn the ignition switch to OFF.

Disconnect the connectors from ECM and rear oxygen sensor.

Measure the resistance of harness between ECM and rear oxygen sensor connector.

Connector & terminal

(B137) No. 24 — (B19) No. 3:

(B136) No. 35 — (B19) No. 4:

Is the resistance more than 3 Ω?

Yes

Repair open circuit in harness between ECM and rear oxygen sensor connector.


No


CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR.

Turn the ignition switch to OFF.

Disconnect the connector from rear oxygen sensor.

Turn the ignition switch to ON.

Measure the voltage between rear oxygen sensor harness connector and engine ground or chassis ground.

Connector & terminal

(B19) No. 3 (+) — Engine ground (−):

Is the voltage 0.2 — 0.5 V?

Yes

Replace the rear oxygen sensor.


No

• Repair harness and connector.

•
Note

In this case, repair the following:

• Open circuit in harness between rear oxygen sensor and ECM connector

• Poor contact in rear oxygen sensor connector

• Poor contact in ECM connector



CHECK EXHAUST SYSTEM.

Check exhaust system parts.

Note

Check the following items.

• Loose installation of portions

• Damage (crack, hole etc.) of parts

• Looseness and ill fitting of parts between front oxygen (A/F) sensor and rear oxygen sensor


Is there a fault in exhaust system?

Yes

Repair or replace faulty parts.


No

Replace the rear oxygen sensor.