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P0052 Generic (SAE)

HO2S Heater Control Circuit High (Bank 2 Sensor 1)

Updated 2026-10-02 · Fuel, air metering & auxiliary emission controls

Severity
Medium
Typical repair cost
30 – 600 EUR
System
Powertrain

What it means

When the ECU grounds the heater control wire of the bank 2 upstream sensor it expects the feedback voltage to drop close to 0 V. P0052 is set when the voltage remains high while the driver is commanded on. The causes are a control wire shorted to battery positive, an open circuit (heater or wire) that leaves the line floating at supply level, a high-resistance connection, or a failed ECU driver.

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Symptoms

  • Check Engine light on
  • Bank 2 enters closed loop later than bank 1 after a cold start
  • Marginally higher fuel consumption and cold idle roughness
  • Possible blown heater fuse if the short to 12 V feeds back into the circuit
  • Heater duty cycle shown at 100 % on the scanner with 0 A current

Common causes

  1. Open heater element in the bank 2 upstream sensor (line floats high)
  2. Heater control wire shorted to a 12 V wire in the harness, often after chafing on the bank 2 exhaust manifold heat shield
  3. Broken wire or terminal pushed out of the connector on the bank 2 sensor or at the ECU
  4. Corroded connector creating high resistance so the driver cannot pull the line down
  5. Failed heater driver transistor in the ECU
  6. Incorrectly wired universal replacement sensor

How to diagnose

  1. Unplug bank 2 sensor 1 and measure heater resistance: 2-15 ohm at 20 °C, matching bank 1 sensor 1 within about 1 ohm. Open circuit means the sensor heater has failed and explains the 'high' reading.
  2. Inspect the connector: pins fully seated, no corrosion, no water. On a previously replaced universal sensor verify the heater wires are in the heater cavities, not the signal cavities.
  3. Key on, sensor unplugged: measure the control pin on the harness side to ground. Use the scanner's actuator test or start the engine to command the heater on; the voltage must drop below 1 V. If it stays at 12-14 V, the wire is shorted to B+ or the ECU driver is open.
  4. Unplug the ECU and measure the control wire: continuity to the ECU pin under 1 ohm, no continuity to any 12 V wire in the harness, no continuity to ground.
  5. Reconnect everything and measure heater current at idle: 0.8-2 A (3-4 A on wideband at start). Zero current while the heater is commanded on confirms an open path or a failed driver.
  6. If the sensor and harness pass, back-probe the ECU pin during the heater command; a pin that never goes low means the ECU driver is faulty and needs repair or ECU replacement.

Frequently asked questions

The code says 'high' but my sensor measures open circuit. Is that consistent?

Yes. Many ECUs bias the heater control line toward supply voltage internally; with an open heater the line cannot be pulled down and the ECU reports 'circuit high'. Replace the sensor.

Could P0052 damage the ECU?

A short to 12 V on the control wire can overload the driver transistor if left for a long time. Find and repair the short promptly to protect the ECU.

Related codes

P0050P0051P0155P0032P0058

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