P0138 – OBD-II DTC

OBD-II DTC P0138 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)

DTC P0138 meaning

DTC P0138 refers to a diagnostic trouble code indicating a low voltage condition in the oxygen sensor circuit for Bank 1 Sensor 2. This sensor is typically located after the catalytic converter and is responsible for monitoring the efficiency of the catalytic converter by measuring the oxygen levels in the exhaust gases. A low voltage reading suggests that the sensor is not functioning properly or that there is an issue in the circuit.

DTC P0138 symptoms

Common symptoms associated with DTC P0138 may include:

• Check Engine Light illuminated
• Decreased fuel efficiency
• Rough engine idle
• Increased emissions
• Potential failure of emissions test

DTC P0138 causes

Several factors can lead to the occurrence of DTC P0138, including:

• Faulty oxygen sensor (Bank 1 Sensor 2)
• Wiring issues such as shorts or open circuits
• Corroded or damaged connectors
• Exhaust leaks before the sensor
• Faulty engine control module (ECM)

DTC P0138 seriousness

DTC P0138 is considered a moderate to serious issue. While it may not cause immediate engine damage, it can lead to:

• Increased fuel consumption
• Higher emissions output
• Potential damage to the catalytic converter over time
• Failure to pass emissions testing

How to diagnose DTC P0138

To diagnose DTC P0138, follow these steps:

1. Use an OBD-II scanner to confirm the code and check for any additional codes.
2. Inspect the wiring and connectors for Bank 1 Sensor 2 for any visible damage or corrosion.
3. Test the voltage output of the oxygen sensor using a multimeter.
4. Check for exhaust leaks that may affect sensor readings.
5. Verify the operation of the engine control module (ECM) if no other issues are found.

How to fix DTC P0138 step-by-step instructions

To fix DTC P0138, follow these steps:

1. Clear the trouble code using an OBD-II scanner.
2. Inspect and repair any damaged wiring or connectors related to Bank 1 Sensor 2.
3. Replace the faulty oxygen sensor if it is determined to be defective.
4. Fix any exhaust leaks that may be present.
5. Recheck the system by running the vehicle and monitoring for any reoccurrence of the code.

How to erase DTC P0138

To erase DTC P0138, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear Codes” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the vehicle to ensure the code does not return.

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