P2574 Catalytic converter: signal or voltage too low

By: Diagno editorial team · Updated: 2026-10-15

P2574 means: Catalytic converter: signal or voltage too low. The catalytic converter cleans the exhaust gas. OK to drive, but have it checked soon. The most common repair costs about €45–90 in Estonia, depending on make and model. The most common cause: connector loose, damp or corroded.

What it means

The catalytic converter cleans the exhaust gas. The computer compares the oxygen sensors before and after it and found that it no longer cleans well enough. The signal voltage is too low. Usually a wire is broken, a connector is loose or a wire is shorted to ground.

What you may notice

• Engine light on
• Emissions fail the inspection
• Sometimes a rotten-egg smell
• Less power if it's blocked

What could be wrong

1. 1Connector loose, damp or corroded · Wiring or connector repair €45–90
2. 2Wire broken or shorted to ground · Wiring or connector repair €45–90
3. 3Faulty sensor · Sensor replacement €80–160
4. 4Engine computer fault (rare) · Control unit check and software €150–300

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Before replacing an expensive converter, have the oxygen sensors and exhaust leaks checked. That often saves hundreds of euros. Best left to a workshop. It needs a diagnostic tool and experience.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the sensor

Standard SAE description: Direct Ozone Reduction Catalyst Deterioration Sensor Circuit Low