Toyota Corolla: Catalytic Converter Failure Secondary to Oil Burning (1ZZ-FE)

ZZE122 Corollas with unrepaired 1ZZ-FE oil consumption frequently present with a destroyed catalytic converter as a secondary failure. Burnt engine oil coats and poisons the catalyst substrate, causing it to melt or block internally. A blocked cat restricts exhaust flow and can cause engine power loss, overheating and further damage. Replacement cats on these cars are expensive, and fitting a new cat without fixing the underlying oil consumption will repeat the failure. Often diagnosed when the vehicle fails an emissions test or triggers a P0420 code.

• Check engine light with P0420 (catalyst efficiency below threshold) code
• Rotten egg smell from exhaust
• Reduced engine power under load
• Rattling sound from beneath the car (broken substrate)

1. 1

   Scan for fault codes, especially P0420.

2. 2

   Inspect catalyst housing for heat discolouration or physical damage.

3. 3

   Shake the exhaust to detect substrate rattle.

4. 4

   Cross-reference with oil consumption history — a failed cat almost always points to a burning engine.

Parts involved: Catalytic converter.

$800 to $2,200 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the check engine light been on, and what codes were stored?”
• “Has the catalytic converter been replaced?”
• “How much oil does the engine use between services?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.