Fault code P0143 – a step-by-step guide to diagnosing and fixing it

The meaning of error code P0143 – O2 Sensor Circuit Low Voltage (Bank 1 Sensor 3)

P0143: Causes, signs and repairs

Error code P0143 is displayed and the check engine light is on - what does this mean?

With this DTC, the OBD/EOBD system detects insufficient voltage in the circuit of lambda sensor 3, bank 1. This indicates problems with the rear lambda sensor after the catalytic converter, which is responsible for monitoring exhaust gas purification.

What causes can this error code have?

Defective lambda sensor 3 (bank 1)
Damaged cable connections to the lambda sensor
Corroded or loose plug connections
Short circuit in the wiring
Defective engine control unit (ECM)
Broken ground wire of the lambda sensor
Damaged wiring harness due to heat
Defective lambda sensor heater

What symptoms occur in parallel with fault code P0143?

Increased fuel consumption: The vehicle consumes more fuel than usual due to incorrect mixture control.
Poor engine performance: Reduced acceleration and rough engine running, especially at higher engine speeds.
Exhaust problems: Increased pollutant emissions and possible failure of the emissions test.
Jerking at idle: Irregular engine running at idle and when accelerating.
Starting problems: Difficult cold starting characteristics, especially at low temperatures.

How can the problem with error code P0143 be rectified?

Repairing this trouble code requires a systematic diagnosis of the lambda sensor and its electrical connections.
Replacement of the defective lambda sensor 3 on bank 1 with an OEM spare part or equivalent component
Repair or replacement of damaged cable connections between lambda sensor and engine control unit
Cleaning and treatment of corroded plug connections with contact spray and subsequent sealing
Repairing short circuits in the wiring by replacing the affected cable section
Checking and repairing the earth connection of the lambda sensor to the vehicle chassis
Replacement of the complete wiring harness in the event of extensive heat damage or corrosion
Programming or replacement of the engine control unit in the event of proven internal defects

FAQ - Frequently asked questions about DTC P0143

Can I continue driving with fault code P0143?

It is possible to continue driving for a short time, but the fault code should be rectified as soon as possible. The defective lambda sensor can lead to increased fuel consumption and engine damage.

How much does it cost to repair fault code P0143?

The costs vary between 150-400 euros. A new lambda sensor costs 80-200 euros, plus 70-200 euros in labor costs depending on the workshop and vehicle type.

How do I recognize a defective lambda sensor with code P0143?

Typical signs are increased fuel consumption, poor exhaust gas values, irregular engine running and the illuminated engine control light. An OBD diagnosis confirms the defect.

Can I change the lambda sensor for P0143 myself?

With the right tools and experience, you can repair it yourself. The correct tightening torques and the use of assembly paste for the threads are important.

How long does a lambda sensor normally last?

Lambda sensors have a service life of 80,000-160,000 kilometers. Code P0143 usually affects the rear sensor, which is stressed by exhaust gases and heat.

Does error code P0143 lead to an MOT failure?

Yes, this EOBD code can lead to failure during the emissions test, as the lambda sensor is essential for emission control and OBD readiness is impaired.

Vehicles in which error code P0143 occurs most frequently

Error code P0143 is a cross-manufacturer DTC that indicates problems with the rear lambda sensor and can occur in various vehicle brands, but is most common in the following vehicles:

BMW: 3 Series, 5 Series, X3, X5 (2000-2010)
Mercedes-Benz: C-Class, E-Class, ML-Class, GLK (2002-2012)
Audi: A4, A6, Q5, Q7 (2001-2011)
Volkswagen: Golf, Passat, Tiguan, Touareg (2000-2010)
Ford: Focus, Mondeo, Kuga, S-Max (2004-2014)
Opel: Astra, Vectra, Insignia, Antara (2003-2013)
Toyota: Avensis, RAV4, Prius, Camry (2000-2012)
Honda: Civic, Accord, CR-V, FR-V (2002-2011)
Nissan: Primera, X-Trail, Qashqai, Navara (2001-2010)
Mazda: 6, CX-5, CX-7, MPV (2002-2012)

If code P0143 occurs in your vehicle, you should first have the lambda sensor and its wiring checked. Early diagnosis can prevent expensive consequential damage to the catalytic converter or engine. In older vehicles, a total economic loss can often be avoided if the defect is detected in good time.

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