P1143 – OBD-II DTC

OBD-II DTC P1143 – Lack Of HO2S12 Switch – Sensor Indicates Rich

DTC P1143 meaning

DTC P1143 refers to a diagnostic trouble code indicating a lack of response from the heated oxygen sensor (HO2S) located in the exhaust system. Specifically, it suggests that the sensor is indicating a rich fuel mixture condition, meaning that there is an excess of fuel in the air-fuel mixture being burned in the engine. This code is typically associated with the second oxygen sensor (HO2S12) in the exhaust system.

DTC P1143 symptoms

Common symptoms associated with DTC P1143 may include:

• Check Engine Light illuminated
• Decreased fuel efficiency
• Rough engine idle
• Increased emissions
• Possible engine stalling

DTC P1143 causes

Several factors can lead to the triggering of DTC P1143, including:

• Faulty heated oxygen sensor (HO2S12)
• Wiring issues or poor connections in the sensor circuit
• Exhaust leaks before the sensor
• Fuel system problems, such as a malfunctioning fuel injector
• Engine control module (ECM) issues

DTC P1143 seriousness

DTC P1143 is considered a moderate to serious issue. While it may not cause immediate engine failure, it can lead to:

• Increased fuel consumption
• Higher emissions, potentially failing emissions tests
• Long-term engine damage if not addressed

How to diagnose DTC P1143

To diagnose DTC P1143, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the P1143 code.
2. Inspect the wiring and connectors of the HO2S12 for damage or corrosion.
3. Check for exhaust leaks in the system before the sensor.
4. Test the HO2S12 using a multimeter to ensure it is functioning correctly.
5. Examine the fuel system for issues, such as clogged injectors or incorrect fuel pressure.
6. Review the ECM for any software updates or faults.

How to fix DTC P1143 step-by-step instructions

To fix DTC P1143, follow these steps:

1. Repair or replace any damaged wiring or connectors related to the HO2S12.
2. Fix any exhaust leaks found during diagnosis.
3. If the HO2S12 is faulty, replace it with a new sensor.
4. Address any fuel system issues, such as cleaning or replacing fuel injectors.
5. Clear the DTC using an OBD-II scanner and perform a test drive to ensure the issue is resolved.

How to erase DTC P1143

To erase DTC P1143, 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 DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the engine to verify that the code does not return.

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