P2237⛽ Fuel and air metering (upstream oxygen / air-fuel ratio sensor)Stop and fix promptly

P2237: O2 Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1 (Meaning, Causes, Fixes)

Reviewed 2026-10-24 · Based on 3 cited source(s)

What P2237 means

The upstream oxygen sensor (bank 1, sensor 1) sits in the exhaust before the catalytic converter and tells the engine computer how rich or lean the engine is running, so it can adjust fuel. OBD-Codes.com explains that P2237 is stored when the computer sees a voltage on the sensor's positive current control circuit that is outside acceptable limits, and that most vehicles need the failure on more than one drive cycle before the light comes on. RepairPal describes it more broadly: the computer has detected a failure of the sensor or of the information it receives from it. Toyota's 2007 Land Cruiser service manual is more specific. It notes that although the code title says "oxygen sensor", on its engines P2237 relates to the air-fuel ratio (A/F) sensor, and it sets the code when there is an open in the circuit between the sensor's A/F+ and A/F- terminals while the engine is running, using two-trip logic. Toyota calls the code "Oxygen (A/F) Sensor Pumping Current Circuit / Open". So the exact trigger depends on your make; check the factory procedure for your vehicle.

Severity: can I keep driving?

Stop and fix promptly

Get it fixed soon. The sources disagree on how urgent it is: OBD-Codes.com classifies P2237 as severe because a bad upstream sensor circuit can make the engine run poorly, while RepairPal rates it Moderate. Either way the engine computer is losing its main air-fuel feedback, which hurts fuel economy and performance, and the check engine light will fail an emissions inspection.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. A failed upstream oxygen or A/F sensor (OBD-Codes.com, RepairPal, Toyota)
  2. Burnt, chafed, broken or disconnected wiring or connectors in the sensor circuit (OBD-Codes.com, RepairPal, Toyota)
  3. An exhaust leak (RepairPal only)
  4. A faulty engine computer (PCM/ECM) or a programming error, which is rare (OBD-Codes.com, RepairPal, Toyota)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Read all stored codes and freeze frame data and write them down, since the fault can be intermittent. Diagnose any related sensor heater codes as well.
  2. Clear the code and test drive. If it does not come back right away, the problem may be intermittent and harder to pin down.
  3. Find the bank 1 upstream sensor (ahead of the catalytic converter on the side with cylinder 1) and inspect its connector and wiring for burns, chafing, corrosion or a loose plug, especially near hot exhaust parts.
  4. Check for exhaust leaks ahead of the sensor.
  5. With the sensor unplugged, OBD-Codes.com suggests using a multimeter to check for continuity between the positive current control circuit and ground; continuity points to a defective sensor. Use the factory wiring diagram for your vehicle.
  6. With the engine warm, watch the upstream sensor data on a scan tool. A sensor stuck at battery voltage or at zero points to an internal short or wiring problem. Note that wide-range A/F sensors read differently from ordinary oxygen sensors, so compare against the specs for your engine.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • You don't have a scan tool that shows live sensor data or the factory wiring diagram
  • The sensor is seized in the exhaust and hard to remove
  • The code returns after replacing the sensor
  • The engine is running poorly or you need the light off for an inspection deadline

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Is P2237 serious?

The sources disagree. OBD-Codes.com classifies it as severe because the engine may run poorly, while RepairPal rates it Moderate. It usually won't leave you stranded, but it hurts fuel economy and performance and will fail an emissions test, so fix it soon.

Which sensor is bank 1 sensor 1?

It is the upstream sensor, ahead of the catalytic converter, on the side of the engine that has cylinder 1. On a 4-cylinder engine there is only one bank.

Is P2237 an oxygen sensor or an air-fuel ratio sensor code?

Both, depending on the car. The generic title says oxygen sensor, but Toyota's service manual notes that on its engines the code relates to the wide-range air-fuel ratio (A/F) sensor.

How much does it cost to fix P2237?

None of these sources give a repair cost. It depends on whether it's a wiring repair or a new sensor and on your vehicle, so get a written estimate after diagnosis.

Sources

  1. OBD-Codes.com: P2237 O2 Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1 (Stephen Darby, ASE)
  2. RepairPal: P2237 O2 Sensor Positive Current Control Circuit/Open (rated Moderate)
  3. Toyota 2007 Land Cruiser service manual (2UZ-FE): DTC P2237 Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.