P0142 OBD-II Trouble Code: O2 Sensor Circuit Malfunction (Bank 1, Sensor 3)

Diagnostic Trouble Code (DTC): P0142

P0142 code definition

O2 Sensor Circuit Malfunction (Bank 1, Sensor 3)

What the P0142 code means

P0142 is the OBD-II generic code indicating the Engine Control Module (ECM) input from the O2 sensor circuit for bank 1 sensor 3 is not within specifications.

What causes the P0142 code?

• The O2 sensor bank 1 sensor 3 is downstream of the last catalyst in the exhaust system; an exhaust leak before the sensor can cause the code from excessive oxygen getting into the exhaust stream.

• The ECM detects a short or open circuit in the O2 bank 1 sensor 3 circuit.

What are the symptoms of the P0142 code?

• The ECM does not use the input from this O2 sensor for controlling the engine fuel control, so this code should not account for any abnormal drive complaints.

• The Check Engine Light will be illuminated, indicating a problem with the downstream catalyst O2 sensor 3 for bank 1.

How does a mechanic diagnose the P0142 code?

• Checks electrical connections to the O2 bank 1 sensor 3

• Checks the exhaust system before the O2 sensor for any exhaust leaks

• Scans to see if codes P0143 and P0144 are present, or if the problem is intermittent, and can be ignored unless the problem returns

Follows the manufacturer's specific pinpoint tests for further diagnosis

Common mistakes when diagnosing the P0142 code?

Follow these simple guidelines to prevent misdiagnosis of code:

• Scan for codes P0143 and P0144, and repair these codes first to complete the diagnosis.

• Check for any exhaust leaks or damages to the exhaust before the O2 sensor that could cause the sensor to not work properly.

How serious is the P0142 code?

• The code is for the sensor behind the last catalyst on bank 1 of the exhaust and may contribute to an excessive exhaust emission if the problem is the catalyst.

• The code will not cause the engine to run any different in most circumstances.

• The vehicle will fail emission testing, since the Check Engine Light is on.

• The exhaust may have a leak and cause fumes to get into the passenger compartment.

What repairs can fix the P0142 code?

• Checking and repairing exhaust leaks before the catalyst

• Repairing or replacing the wiring or connection to the O2 sensor for bank 1 sensor 3

• Replacing the O2 sensor

Additional comments for consideration regarding the P0142 code

The code P0142 will not cause a driveability problem since the code is in relation to the last catalyst in the exhaust performance; it is for cleaning the exhaust stream only, not for engine fuel control.

Need help with a P0142 code?

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