P0433: Heated Catalyst Efficiency Below Threshold (Bank 2)
Quick Answer
Safe to drive (short-term)
P0433 means the heated catalyst on Bank 2 is not converting emissions as efficiently as the ECU expects. A heated catalyst has an electric heating element that brings it to working temperature within seconds of a cold start. The code needs an engine with two banks, each with its own catalyst (V engines, boxers and some inline engines that split their exhaust in two), plus a heated catalyst on the second bank, which is still uncommon on production cars, so check the manufacturer's definition of the code for your vehicle.
- Severity
- Moderate · Emissions
- Estimated repair cost
- From €130 to €2560+, varies by vehicle
€130 or €2560, depending on your car.
- Fix exhaust leak on Bank 2 (gasket or flex pipe)€130–€370
- Replace heated catalytic converter (Bank 2)€790–€2560
A scan shows whether P0433 is really stored on your car, which codes sit next to it and how urgent each one is.
A scan needs a Bluetooth OBD2 adapter (Bluetooth LE on iPhone), about €25-60; the built-in demo runs without one. See which adapter to buy
What does P0433 mean?
P0433 is a emissions-related diagnostic trouble code classified as moderate severity.
Where it is on the car
- Engine
- Oxygen sensor before the converter (sensor 1)
- Catalytic converter
- Oxygen sensor after the converter (sensor 2, or 3 on some cars)
- Silencer and tailpipe
This code is for bank 2. V6, V8 and flat engines have two cylinder banks, each with its own converter and sensors; bank 2 is the side without cylinder 1.
What are the symptoms of P0433?
- Check engine light illuminated, often within the first minute after start
- Higher exhaust emissions during warm-up (not usually noticeable from the driver's seat)
- Slight reduction in fuel economy
- Possible faint sulfur smell during warm-up
- Failed emissions test or periodic technical inspection
What causes P0433?
Failed Bank 2 e-cat heater element or substrate degradation
: high
Faulty downstream O2 sensor (Bank 2, Sensor 2)
: medium
Wiring or connector fault in the Bank 2 heater circuit, or a failed heater relay or control module
: medium
Prior misfire on Bank 2 cylinders damaging the heated brick
: low
Oil consumption from Bank 2 fouling the substrate
: low
Is it safe to drive with P0433?
Generally yes, for short-term driving. Safe for short-term driving. P0433 needs a second cylinder bank with its own heated catalyst, so it only applies to a small number of vehicles. Emissions are higher during warm-up, and a stored catalyst code with the check engine light on is the kind of defect that gets a car rejected at an emissions check.
How do you diagnose P0433?
- Confirm the engine has a second bank with its own catalyst and that a heated catalyst is fitted there; if not, look up the manufacturer's definition of the code and recheck the reading
- Read freeze frame and confirm the code triggered shortly after cold start, which is typical of heated catalyst faults
- Check for companion codes such as P0434 (heated catalyst temperature below threshold, Bank 2) or manufacturer-specific heater circuit codes
- Measure the resistance of the Bank 2 heater element and compare it with the manufacturer specification
- Graph the Bank 2 downstream O2 sensor after a cold start and compare its behaviour with the manufacturer's data: a working catalyst settles the downstream signal quickly, while a failing one lets it follow the upstream sensor
How much does P0433 cost to fix?
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace heated catalytic converter (Bank 2) | €650–€2200 | €140–€360 | €790–€2560 | Professional |
| Replace downstream O2 sensor (Bank 2) | €65–€190 | €70–€150 | €135–€340 | Moderate |
| Fix exhaust leak on Bank 2 (gasket or flex pipe) | €30–€130 | €100–€240 | €130–€370 | Moderate |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Related diagnostic codes
Common questions about P0433
- Which engines actually have a heated catalyst on Bank 2?
- Very few. The code needs an engine with two banks, each with its own catalyst, and a heated catalyst on the second bank. Suppliers offer heated catalysts mainly for hybrid and 48 V mild-hybrid systems and they are still uncommon on production cars, so check your vehicle's documentation or the manufacturer's definition of the code before ordering parts. An engine with a single bank cannot set a genuine Bank 2 code.
- Why does only Bank 2 set P0433 when both banks have e-cats?
- The two banks have separate heater circuits and separate downstream O2 sensors. If a single wire, connector, or heater element fails on Bank 2 alone, only Bank 2 will set the code. Fuel-trim asymmetry between banks (caused by intake manifold geometry or injector wear) can also age one bank's heated cat faster than the other.
- Can a 48V mild-hybrid system fault trigger P0433?
- Yes, where the heater is supplied from a 48V system. A weak 48V battery, a degraded DC-DC converter or a starter-generator fault can starve the Bank 2 heater of current and trigger P0433. Check the supply before replacing the catalyst itself.
- Will my warranty cover a P0433 repair?
- EU type approval sets durability requirements for emission control devices under Regulation (EC) 715/2007 and the later Euro 6 steps that amend it, and the exact period depends on which standard the car was approved to. That is a requirement on the manufacturer rather than a warranty you claim directly, but many manufacturers do offer a separate emissions warranty on top of the standard vehicle warranty, and heated catalysts are usually covered by it. Check your service book or ask the dealer for the terms that apply to your car before paying for an out-of-warranty replacement.