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DTC codes / Volkswagen codes / P1118

P1118 · VolkswagenOxygen Sensor Heater Circuit Open Bank 1 Sensor 2

P1118 on Volkswagen vehicles means the engine control module has detected an open circuit in the heater element of the downstream oxygen sensor on bank 1, which is the sensor after the catalytic converter. The heater is a resistive element inside the sensor that brings it up to operating temperature quickly, and an open circuit means the control module sees no current flow through that heater circuit when it commands it on.

SystemPowertrain
Code typeVolkswagen specific
SeverityLow
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illuminated check engine light, often the only noticeable symptom
  • Slightly higher fuel consumption during cold starts because the downstream sensor stays cold longer
  • A pending or stored P1118 with no drivability complaint in most cases
  • Occasional rough running or hesitation during the first minute after a cold start on some cars
  • In rare cases, a slight exhaust smell or elevated emissions at idle when the sensor never reaches temperature

Common causes, most likely first

  1. Failed heater element inside the bank 1 sensor 2 oxygen sensor
  2. Broken or corroded wire in the sensor heater circuit between the sensor and the control module
  3. Loose, water-intruded or backed-out terminal at the oxygen sensor connector
  4. Blown fuse or faulty relay supplying power to the oxygen sensor heater circuit
  5. Damaged pin or open trace inside the engine control module heater driver, usually after a shorted sensor
  6. Rodent damage or chafing of the heater wiring harness near the exhaust or underbody

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm the fault is present and not a historic memory
  2. Inspect the bank 1 sensor 2 connector and harness for corrosion, water intrusion, chafing or rodent damage
  3. Check the oxygen sensor heater fuse and relay, then verify battery voltage at the heater supply wire with the key on
  4. Measure heater resistance across the sensor-side heater terminals and compare with the Volkswagen specification for that engine
  5. With the sensor disconnected, check for continuity and voltage drop on the ground and signal-return side of the heater circuit back to the control module
  6. If wiring and supply check out, replace the bank 1 sensor 2 oxygen sensor with the correct part for the engine code
  7. Clear the fault memory, run a cold-start readiness cycle and confirm the heater monitor passes without the code returning

What the heater circuit test really checks

  • A P1118 can be set by a heater circuit that is open only when cold, so a resistance check on a warm engine may look normal and send you chasing the wrong part.
  • Volkswagen control modules often set this code when the heater driver has been damaged by a shorted sensor, so replacing the sensor without checking the driver can leave the new sensor dead on arrival.
  • The downstream sensor heater is not needed for fuel control, which is why many cars with P1118 drive perfectly normally and the fault is missed until an emissions test.
  • Corrosion inside the connector pins at the sensor is a common cause on cars that see road salt, and it can mimic a failed heater even when the sensor element itself is good.
  • A P1118 on some Volkswagen engines can be triggered by a low or weak battery during cranking, so check charging system health before condemning the sensor.

Can I keep driving with P1118?

The car is safe to drive with P1118 because the downstream heater only affects emissions readiness and cold-start sensor response, not immediate engine safety. Avoid long periods of short cold-start trips until it is repaired, and get it diagnosed before an emissions inspection because the monitor will not complete.

Tools that help

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Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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