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DTC codes / P22xx · Fuel and air metering (injector circuits) / P2237

P2237O2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)

P2237 indicates that the engine control module (ECM) has detected an open circuit or excessive current draw in the positive current control circuit for the upstream oxygen sensor on bank 1. The sensor's heater or pump cell current is not within the expected range, which can affect fuel control and emissions.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Rough idle or hesitation during acceleration
  • Poor fuel economy
  • Failed emissions test due to increased emissions
  • In rare cases, a rich or lean running condition that may cause surging

Common causes, most likely first

  1. Open or damaged wiring in the oxygen sensor positive current control circuit
  2. Corroded or loose electrical connector at the oxygen sensor or ECM
  3. Failed oxygen sensor (internal open circuit or short)
  4. Blown fuse or relay supplying power to the oxygen sensor heater circuit
  5. Faulty ECM driver for the current control circuit (less common)
  6. Exhaust leaks before the sensor causing incorrect readings

How to diagnose and fix it

  1. Inspect the oxygen sensor wiring and connector for damage, corrosion, or loose pins
  2. Check the fuse and relay for the oxygen sensor heater circuit
  3. Measure resistance of the oxygen sensor heater circuit and compare to specifications
  4. Perform a voltage drop test on the positive current control circuit to detect excessive resistance
  5. Test the sensor's current draw with a scan tool or oscilloscope to verify operation
  6. Replace the oxygen sensor if tests indicate an internal fault
  7. If the sensor and wiring are good, diagnose the ECM driver circuit for faults

Don't overlook the sensor heater circuit

  • A common oversight is assuming the oxygen sensor itself is faulty when the real problem is a corroded connector or chafed wire in the current control circuit.
  • The code can set intermittently due to vibration or temperature changes, so a wiggle test of the harness while monitoring live data is often revealing.
  • Some vehicles use a fused power supply for the oxygen sensor heater; a blown fuse may cause this code without any other symptoms.
  • Exhaust leaks upstream of the sensor can alter the current feedback and trigger P2237, so always check for leaks before replacing parts.
  • The ECM may set this code if the sensor's return circuit has high resistance, which can be caused by a poor ground connection.

Can I keep driving with P2237?

You can usually drive the vehicle with this code, but avoid aggressive acceleration or heavy loads until it is repaired. Prolonged driving may lead to increased emissions and reduced fuel economy, and if drivability symptoms appear, have it checked promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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