Emissions

P0059 — O2 Sensor Heater Resistance (Bank 2, Sensor 1)

Severity: medium Safe to drive

What P0059 means

The engine computer monitors the heater circuit inside the upstream oxygen sensor on Bank 2. The heater brings the sensor to operating temperature quickly so the engine can enter closed-loop fuel control soon after a cold start. P0059 sets when the circuit resistance is outside the expected range, due to the heater element, wiring, connector or fuse.

Symptoms

  • Check Engine light on
  • Reduced fuel economy
  • Rough idle or hesitation
  • Delayed closed-loop operation after a cold start
  • Higher emissions
  • Unstable idle

Possible causes

  1. Failed heater element in the Bank 2 Sensor 1 oxygen sensor
  2. Open or shorted wiring or connector in the heater circuit
  3. Blown fuse or faulty heater relay
  4. Poor connection or corrosion at the sensor or harness
  5. PCM fault (rare)

How to diagnose

  1. Read codes and freeze-frame data, and confirm which side of the engine is Bank 2 (the side with cylinder #2).
  2. Inspect the sensor harness and connector for chafing, melting, corrosion or pushed-out pins.
  3. Check the heater fuse and relay using the vehicle wiring diagram.
  4. Measure heater resistance at the sensor terminals and compare it with the spec.
  5. Check for power and the control ground signal at the harness connector with the ignition on.
  6. Test the wires to the PCM for opens and shorts to ground or power.
  7. Review fuel trims on a scan tool and look for exhaust leaks near the sensor.
  8. Clear the code after repair and confirm it does not return.

Common fixes

  • Replace the Bank 2 Sensor 1 oxygen sensor
  • Repair damaged wiring or the connector
  • Replace the blown fuse or faulty relay (after ruling out a short)
  • Repair or replace the PCM (very rare)

Questions and answers

What does P0059 mean?

The PCM sees abnormal resistance in the heater circuit of the upstream oxygen sensor on Bank 2. The cause is usually the sensor, its wiring or a fuse.

Can I drive with P0059?

Yes, for a short time. The engine will control the mixture less accurately while warming up, so fuel use and emissions go up. Don't put the repair off for long.

Do I always need a new oxygen sensor?

No. Check the fuse, connector, wiring and heater resistance first. Replace the sensor only if the heater element is faulty.

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.