Emissions

P0055 — HO2S Heater Resistance (Bank 1, Sensor 3)

Severity: low Safe to drive

What P0055 means

The engine control module monitors the heater circuit of the Bank 1, Sensor 3 oxygen sensor, which is usually located well downstream of the catalytic converter. The heater brings the sensor up to operating temperature quickly so it can report exhaust data. P0055 sets when the heater circuit resistance is outside the expected range, such as from an open circuit, short, or a worn heater element.

Symptoms

  • Check Engine light on
  • Possible slight drop in fuel economy
  • Failed emissions or inspection test
  • Occasionally an unstable idle
  • Often no other noticeable symptoms

Possible causes

  1. Failed heater element inside the Bank 1 Sensor 3 oxygen sensor
  2. Damaged, chafed or corroded wiring or connector
  3. Blown fuse or faulty relay in the heater supply
  4. Heat, oil or moisture damage at the connector
  5. Faulty driver in the ECM (rare)

How to diagnose

  1. Scan for codes and freeze-frame data and check for other oxygen sensor codes
  2. Locate Bank 1 Sensor 3 using a diagram for your specific vehicle
  3. Inspect the harness and connector for chafing, melting, corrosion or exhaust soot
  4. Check the heater fuse and relay
  5. Measure heater resistance across the sensor terminals and compare it with the factory spec
  6. Check for power and control signal at the harness connector and test wire continuity to the ECM
  7. Look for exhaust leaks near the sensor
  8. Clear the code and road test after the repair

Common fixes

  • Replace the Bank 1 Sensor 3 oxygen sensor
  • Repair or replace damaged wiring or the connector
  • Replace the fuse or relay after finding why it failed
  • Repair or replace the ECM if confirmed faulty (rare)

Questions and answers

What does P0055 mean?

It means the heater circuit of the Bank 1 Sensor 3 oxygen sensor has a resistance fault. The usual culprits are the sensor itself or its wiring.

Can I drive with code P0055?

Usually yes, as it rarely causes harm to the engine. Still, fix it soon so you don't miss other problems and can pass an emissions test.

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.