P0424Generic code

P0424 Code: Heated Catalyst Temperature Below Threshold (Bank 1)

The P0424 code means the heated catalytic converter on bank 1 is not reaching the temperature it needs after startup. The heater, its supply or the temperature sensor are the first suspects. Rule out exhaust leaks, slow O2 sensors and mixture problems before you replace the converter.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$100 to $2,500
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0424 code means

The converter heater is supposed to bring it up to working temperature within a short time after startup. The P0424 code says it is not managing to do that, because of a faulty heater, an insufficient supply or a defective temperature sensor.

The computer compares the signal from the upstream sensor with the one from the downstream sensor. If the downstream signal starts to copy the upstream one, the converter is no longer storing oxygen. Before you replace it, rule out exhaust leaks, slow sensors and problems with the mixture or with misfires.

The diagnosis is the same as for the P0420 code, with the heater and the temperature sensor added to the list of things to check.

Before you replace a converter, check the downstream sensor with a simple test. With the engine hot, rev it hard with the vehicle parked, and the sensor should rise above 0.8 volts. Then let off the throttle, and it should drop below 0.2 volts. If it responds that way, the sensor is healthy and the converter is probably worn out. Remember that a new converter will be ruined the same way if you do not fix the oil consumption or the misfires that damaged the old one.

P0424 code symptoms

  • Check engine light on.
  • Usually no driving symptoms.
  • Sulfur (rotten egg) smell from the exhaust.
  • Fails the emissions inspection.

Likely causes of the P0424 code

  1. Converter worn out or contaminated by oil, coolant or misfires.
  2. Exhaust leak ahead of the downstream sensor.
  3. Slow oxygen sensor. An aging sensor can make a healthy converter look worn out.
  4. Mixture out of range. Fuel trims beyond plus or minus 10 percent upset the converter test.
  5. Faulty converter heater on heated converters.

How to diagnose the P0424 code step by step

  1. Read the upstream and downstream sensors with the engine hot.
  2. Look for exhaust leaks.
  3. Check the fuel trims and look for misfires.
  4. Measure the temperature before and after the converter with an infrared thermometer.
  5. Check the heater for resistance and supply.
  6. Test the downstream sensor by revving hard (above 0.8 volts) and letting off (below 0.2 volts).

How to fix the P0424 code

  • Fix leaks, sensors, mixture or misfires first.
  • Replace the converter with one approved for your vehicle.
  • Repair the heater if that is the case.
  • Clear the codes and complete the drive cycle.

Technical reference data

  • Downstream sensor with a healthy converter: nearly steady between 0.5 and 0.8 volts.
  • Converter working temperature: 400 to 800 °C (about 750 to 1,470 °F).
  • These are approximate values, so check the manufacturer data for your engine.

Brand-specific notes

Electrically heated converters are rare. Separate main converters are common on V6 and V8 engines.

P0424 on BMW

Electrically heated catalytic converters show up on some BMW vehicles.

P0424 on Volvo

Electrically heated catalytic converters show up on some Volvo vehicles.

P0424 on V6 and V8 Engines

Separate main converters are common on V6 and V8 engines.

Frequently asked questions about P0424

Can I drive with a P0424 code?
Yes. It normally does not affect driving, but you will not pass an emissions inspection.
How is it different from P0420?
It refers to a specific converter on vehicles that have more than one. The diagnosis follows the same logic.
Do I have to replace the catalytic converter?
Only after you rule out the causes that skew the test, such as exhaust leaks, a slow sensor, a bad mixture or misfires. On this code, check the heater and the temperature sensor first.
How much does it cost to fix P0424?
Between $100 and $2,500, depending on the converter. Diagnosing the P0424 code properly first keeps you from paying for parts you do not need.
What does the P0424 code mean?
It is a generic OBD2 code for heated catalyst temperature below threshold on bank 1. The converter does not reach its working temperature after startup.
Will a P0424 code clear itself?
Not for good. A faulty heater, a weak supply or a bad temperature sensor will bring the code back.

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