P0424: Heated Catalyst Temperature Below Threshold (Bank 1)

P0424 means the temperature of the heated catalyst on Bank 1 (an electrically heated e-cat used on newer Euro 6 and 6d vehicles) is not rising fast enough or not reaching the expected level during cold start. Unlike P0423 which is an efficiency code, P0424 is specifically about the heater not delivering enough thermal energy.

P0424 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0424 and illuminates the check engine light.

If your vehicle has triggered P0424, you may notice one or more of these symptoms:

• Check engine light illuminated, typically within the first minute of cold-start driving
• Long warm-up time before the engine reaches stable operating idle
• Elevated cold-start emissions visible as white-grey vapour for longer than usual
• Slight reduction in fuel economy on short trips
• Failed emissions or periodic technical inspection

Here are the most common causes of P0424, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Safe to drive in the short term. The heated catalyst on Bank 1 is not reaching its target light-off temperature within the expected time, so cold-start emissions are elevated and emissions or periodic technical inspection will fail. If the e-cat heater shorted out, related wiring or fuse damage should be ruled out promptly.

Follow these steps to pinpoint the root cause of P0424:

1. Read freeze frame and confirm the code set during the first 60 to 90 seconds of cold start, which is the typical fault window for P0424
2. Check for any heater-circuit-specific codes (manufacturer-specific) and inspect the relevant fuse, often shared with the e-cat heater relay
3. Measure heater element resistance per OEM spec (typically 0.3 to 2.0 ohms). Open circuit means the element has failed
4. Inspect the wiring harness from the heater relay to the catalyst connector for chafing, water ingress, or melted insulation near the exhaust
5. Use a clamp meter to verify current draw at start (commonly 30 to 80 A briefly). Insufficient current points to a relay, wiring, or 48V supply fault

Repair costs for P0424 vary depending on the root cause and your vehicle. Here are typical estimates:

P0424 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0424 or indicate related issues: