P1129 fault code: what it means

P1129: Oxygen sensors swapped left to right. Common after sensor or exhaust work.

Engine and gearbox (powertrain) · Minor

Usual causes, most likely first

oxygen sensor plugs swapped between banks

P1129 by make

Land Rover

Oxygen sensors swapped left to right. Common after sensor or exhaust work.

Usual causes: oxygen sensor plugs swapped between banks

Porsche

Early DME 5.2: mixture adaptation on cylinders 4-6 hit its lean limit (that bank runs rich). Fix any purge valve fault first.

Usual causes: EVAP purge valve stuck open; leaking injector; faulty MAF signal

What the repair usually costs

Air-fuel ratio / front O2 sensor replace (upstream)NZ$270–NZ$750 · A$260–A$730
O2 sensor replace (downstream / after cat)NZ$180–NZ$480 · A$180–A$460

Not sure what P1129 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.