P0433

What it means

P0433 means the engine control unit has judged that the heated catalyst on bank 2 is not storing and converting exhaust gases as efficiently as it should. It reaches this verdict by comparing the signals from the oxygen sensors before and after the catalyst during a monitoring test. If the downstream sensor switches too much like the upstream one, the catalyst is considered below threshold. Bank 2 is the side of the engine that does not contain cylinder number one.

Symptoms

• Engine warning light on
• Failed emissions test or catalyst monitor not completing
• Slight increase in fuel consumption
• Rotten egg smell from the exhaust
• Reduced power or sluggish acceleration in some cases
• Usually no noticeable change in driveability

Possible causes

• Worn or contaminated bank 2 catalytic converterlikely
• Exhaust leak upstream of or near the bank 2 downstream oxygen sensorpossible
• Faulty or slow bank 2 upstream or downstream oxygen sensorpossible
• Engine misfire or rich or lean running damaging the catalyst or skewing readingspossible
• Damaged wiring or connectors to the bank 2 oxygen sensorsrare
• Oil or coolant being burnt, contaminating the catalystrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, and note any misfire, fuel trim or oxygen sensor codes that need dealing with first.
2. Check that you are looking at the correct bank by confirming which side has cylinder number one for the engine concerned.
3. Inspect the exhaust from manifold to catalyst for leaks, cracks, damaged gaskets and loose joints, particularly around the oxygen sensors.
4. Inspect the wiring and connectors of the bank 2 oxygen sensors for damage, heat melting, corrosion and water ingress.
5. Check fuel trims at idle and at 2500 rpm to spot lean or rich running, and look for misfire counts.
6. Watch live upstream and downstream oxygen sensor signals on bank 2: the downstream should be fairly steady, while a signal mirroring the upstream suggests a tired catalyst.
7. Check for signs of oil or coolant consumption, such as blue smoke, white deposits on spark plugs or falling coolant level.
8. Check for any technical bulletins or calibration updates for the specific model and engine before replacing parts.

How to fix

• Repair any exhaust leaks and replace faulty gaskets.
• Replace a faulty bank 2 oxygen sensor once testing proves it is slow or out of range.
• Repair damaged wiring or connectors.
• Cure any misfire, fuel mixture or oil or coolant consumption fault first, then replace the bank 2 catalytic converter if it has failed.
• Apply a manufacturer calibration update only where one is documented for this fault on the specific model.

Can I keep driving?

Nearby codes

• P0432GenericCatalyst 2 Efficiency Below Threshold Bank 2
• P0434GenericHeated Catalyst Temperature Below Threshold Bank 2