Emissions

P00D4 — O2 Sensor Heater Control Circuit Range/Performance (Bank 2 Sensor 2)

Severity: low Safe to drive

What P00D4 means

The PCM switches power to the heater inside the bank 2 downstream (post-catalytic converter) oxygen sensor so it reaches operating temperature quickly and stays there. P00D4 is set when the heater circuit's current, resistance or response to commands falls outside the expected range. The sensor itself or its wiring is the most common culprit.

Symptoms

  • Check engine light on
  • Slightly higher fuel consumption
  • Failed emissions inspection
  • Occasionally a rough idle or hesitation
  • Other oxygen sensor or catalyst codes stored

Possible causes

  1. Failed heater element in the bank 2 downstream oxygen sensor
  2. Open, shorted or corroded wiring or connector in the heater circuit
  3. Blown fuse or faulty relay supplying the heater
  4. Aged or contaminated sensor
  5. Faulty heater driver in the PCM (uncommon)
  6. Exhaust leak near the sensor affecting readings

How to diagnose

  1. Scan for codes and freeze frame data, and look for other oxygen sensor or catalyst codes
  2. Confirm which sensor is bank 2 sensor 2 (bank 1 is the side with cylinder 1)
  3. Inspect the sensor wiring and connector for melting, chafing, corrosion or water
  4. Check the heater fuse and relay
  5. Measure the sensor heater resistance with a multimeter and compare it to the spec for your vehicle
  6. Check for power and the PCM control signal (ground) at the connector with the ignition on
  7. Look for exhaust leaks near the sensor
  8. Review fuel trims to rule out a rich or lean condition

Common fixes

  • Replace the bank 2 downstream oxygen sensor
  • Repair the wiring or replace a damaged connector
  • Replace the blown fuse or faulty relay
  • Fix any exhaust leak
  • Update PCM software if a manufacturer service bulletin calls for it

Questions and answers

Can I drive with a P00D4 code?

Yes, for a short time it is generally fine, as there is no direct safety risk. Don't put the repair off for long, though, to avoid worse fuel economy and an emissions test failure.

What most often causes P00D4?

Usually a dead heater inside the oxygen sensor or damaged wiring. Check the connector, fuse and heater resistance before buying a new sensor.

Do I need a new catalytic converter for P00D4?

Usually not. This code points to the sensor's heater circuit, not the converter itself, even though the downstream sensor helps monitor the converter.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.