P3143 — 2 documented meanings by make

P3143 does not mean the same thing on every car — manufacturers reuse the number for different faults. 4 makes document it: Audi, SEAT, Skoda, Toyota. Find your make below.

P3143 on Audi, SEAT, Skoda

On Audi, SEAT, Skoda vehicles P3143 is documented as: Oxygen sensor signal implausibly rich, bank 2 sensor 1. P3143 points at oxygen sensor (bank 2, sensor 1). The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Usually one of: Sensor aged and slow to respond; Heater element failed inside the sensor; Wiring or connector fault at the sensor; Exhaust leak near the sensor drawing in air; Engine genuinely running rich or lean.

Check first, cheapest first:

1. Read the sensor's live trace — a lazy or flat signal identifies an aged sensor without removing anything
2. Check for exhaust leaks upstream of the sensor
3. Inspect the connector, which sits in a hot and exposed place and corrodes
4. Measure the heater resistance against specification
5. Replace the sensor once the exhaust and wiring are ruled out

Related Audi, SEAT, Skoda codes:

P3143 on Toyota

On Toyota vehicles P3143 is documented as: Collision sensor high input. P3143 is stored when the ECU sees signal too high on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: Open ground for the sensor, letting the signal float up; Signal line shorted to a supply voltage; Sensor failed open, which the module reads as maximum; Connector fault interrupting the return path.

Check first, cheapest first:

1. Read the live value and compare with what the conditions should produce
2. Check the sensor ground continuity back to the module
3. Unplug the sensor: if the reading changes, the wiring is intact and the sensor is suspect
4. Inspect the connector for corrosion or a spread terminal
5. Replace the sensor once ground and signal wiring are confirmed good

Related Toyota codes:

Which one is yours

A generic OBD reader gives you the number, not which of these meanings your manufacturer assigned to it. To get to the specific one:

1. Use a brand-specific scanner — VCDS for VAG, INPA or ISTA for BMW, XENTRY for Mercedes, Forscan for Ford. It shows the manufacturer's own text rather than the generic one.
2. Read all stored codes together — the neighbouring ones usually point at which system is involved and narrow the list.
3. Check freeze-frame data: the RPM, temperature and load at the moment it triggered indicate which system was active.
4. If you have no brand scanner, tell me the make and model below and I will tell you which of these applies to your car.

Code family

P3xxx is reserved section used by some manufacturers for specific diagnostics.

Severity

Reserved section — the meaning is manufacturer-defined; a generic scanner rarely gives the full picture.

That is what holds for P3143 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.