Honda P0138-Secondary HO2S Sensor Circuit High Voltage

Honda P0138 Secondary Heated Oxygen Sensor HO2S Sensor 2 Circuit High Voltage

Code P0138 Honda is DTC code indicating issue heated oxygen sensor circuit in bank 1 sensor 2. This means that the voltage output from secondary HO2S sensor is consistently above normal operating range.

Fault Location- HO2S Sensor Sensor 2 Bank 1

Possible Causes Code P0138 Honda

1.The most common cause is secondary HO2S sensor failure.

2.Damaged or corroded wiring of secondary HO2S sensor circuit causing high voltage reading.

3.Malfunctioning ECM can cause HO2S sensor circuit to produce high voltage reading.

4.Clogged fuel injector can result in rich air/fuel mixture causing high voltage reading from HO2S sensor.

5.Exhaust leak before HO2S sensor location can cause incorrect reading triggering p0138.

Honda P0138 DTC Code Possible Symptoms

1.Engine check light will illuminate indicating problem with vehicle emissions system.

2.Faulty HO2S sensor can result in less efficient air/fuel mixture ratio causing vehicle to consume more fuel.

3.High voltage reading from secondary HO2S sensor can cause engine to run too lean or too rich resulting reduce engine performance.

4.If HO2S sensor is sending incorrect signal to ECM engine hesitation or stalling can occur.

5.If HO2S sensor is not functioning it causes incorrect air/fuel mixture resulting in engine misfire.

How To Fix Code P0138 Honda

1.If HO2S sensor is the cause of the issue you need to replace the sensor with OEM parts for best result.

2.Any problem with wiring or connector of HO2S sensor such as corroded wire or damaged connector need to be inspected to repaired or replaced as necessary.

3.Inspect and repair fuel system issue such as cleaning the fuel injector, repairing or replacing fuel pump that may be affecting fuel system.

4.If there is an exhaust leak before the location of secondary HO2S sensor it need to be repaired.

5.If issue is caused by malfunctioning ECM engine control module it will need to be replaced.


Its important to have the vehicle inspected and diagnosed by professional mechanic to find and resolve issue related with p0138 for proper repair.

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