P0424: Heated Catalyst Temperature Below Threshold (Bank 1)
Quick Answer
Safe to drive (short-term)
P0424 means the heated catalyst on Bank 1 is not getting hot enough, fast enough, after a cold start. A heated catalyst has an electric heating element that brings it to working temperature within seconds; such catalysts are still uncommon on production cars, so first check the manufacturer's definition of the code for your vehicle. Unlike P0423, which is about how well the catalyst cleans the exhaust, P0424 is about the heater not delivering enough heat, so the usual suspects are the heater element, its fuse, relay or control, and its wiring.
- Severity
- Moderate · Emissions
- Estimated repair cost
- From €120 to €2320+, varies by vehicle
€120 or €2320, depending on your car.
- Repair heater circuit wiring or connector€120–€440
- Replace heated catalytic converter (Bank 1)€720–€2320
A scan shows whether P0424 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 P0424 mean?
P0424 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
What are the symptoms of P0424?
- Check engine light illuminated, typically shortly after a cold start
- Higher exhaust emissions during warm-up (not usually noticeable from the driver's seat)
- Heater circuit codes (manufacturer-specific) stored alongside on some vehicles
- No change in how the car drives in most cases
- Failed emissions or periodic technical inspection
What causes P0424?
Failed e-cat heater element (open or shorted internal heater coil)
: high
Heater circuit wiring fault, broken pin, or corroded connector
: medium
Faulty heater fuse, relay or control module
: medium
Low supply voltage to the heater (on 48V mild hybrids, a weak 48V battery or DC-DC converter)
: low
Cracked or fouled catalyst substrate affecting how quickly it heats up
: low
Is it safe to drive with P0424?
Generally yes, for short-term driving. Safe to drive in the short term. The heated catalyst on Bank 1 is not reaching its target temperature within the expected time after a cold start, so emissions are higher during warm-up and the car is likely to be rejected at an emissions check or periodic technical inspection. If the heater circuit has shorted, have the wiring and fuse checked promptly.
How do you diagnose P0424?
- Read freeze frame and confirm the code set shortly after a cold start, which is when the heated catalyst is monitored
- Check for heater-circuit codes (manufacturer-specific) and inspect the heater fuse and relay
- Measure the heater element resistance and compare it with the manufacturer specification. An open circuit means the element has failed
- Inspect the wiring harness from the heater relay to the catalyst connector for chafing, water ingress, or melted insulation near the exhaust
- Following the manufacturer's procedure, check the heater's current draw or supply voltage during a cold start. Insufficient current points to a relay, wiring or supply fault; switching the heater on for a test needs manufacturer-level software
How much does P0424 cost to fix?
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace heated catalytic converter (Bank 1) | €600–€2000 | €120–€320 | €720–€2320 | Professional |
| Repair heater circuit wiring or connector | €30–€200 | €90–€240 | €120–€440 | Moderate |
| Replace downstream O2 sensor (Bank 1) | €60–€180 | €60–€130 | €120–€310 | Moderate |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Related diagnostic codes
Common questions about P0424
- What is the difference between P0423 and P0424?
- P0423 is an efficiency code (the heated catalyst is not converting emissions well enough), while P0424 is a temperature code (the heater itself is not getting the catalyst hot enough fast enough). P0424 most often points to a wiring, relay, or heater element fault rather than the catalyst substrate.
- Can a fuse cause P0424?
- Yes. The heater draws a high current through its own fuse. If that fuse blows, the heater never switches on and the code can set on the next cold start. Check the heater fuse before assuming the catalyst itself has failed.
- How can I test if the heater element itself is dead?
- With the connector unplugged from the catalyst, measure resistance across the heater terminals with a multimeter and compare it with the manufacturer specification. An open circuit or a resistance well outside spec means the heater element has failed and the catalyst assembly needs replacement.
- Will P0424 trigger limp mode?
- Usually no. Most manufacturers treat P0424 as a non-driveability emissions fault and only illuminate the check engine light. The car will run normally but cold-start emissions will be elevated. Limp mode only triggers if other serious faults are present alongside the heater fault.