P2238: O2 Sensor Positive Current Control Circuit Low (Bank 1 Sensor 1)

P2238 is the low-side fault of the pump-current circuit of the front wide-band sensor on bank 1. Saab's 9-5 2.0 turbo (2010) shows a concrete test: on overrun with the injectors shut off, pure air should drive the signal well above its stoichiometric level, and if it stays below 1.7 V for 3 s the code sets as Type B. GM's 2005 V6 tables use the same fuel-cut check but book it under P2237. Mitsubishi's 2022 Outlander lists P2238 as a two-trip code. Ford does not use it at all: a pump-current wire shorted to ground lands in P0131 there. P2237 is the open circuit, P2239 the high-side fault, P2241 the same on bank 2. Typical findings are a grounded IP wire or a sensor that can no longer pump oxygen.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank. Sensor 1 is the oxygen sensor before the catalytic converter.

Symptoms

• Check engine light after two drives
• Lambda value does not rise during coasting in live data

Most likely causes

• Pump-current wire chafed through to ground
• Aged or contaminated sensor that no longer reads lean in fuel cut-off
• Fault in the sensor interface of the ECM

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2238 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• 38: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2238?

Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.

What causes code P2238?

The most common causes are: pump-current wire chafed through to ground; aged or contaminated sensor that no longer reads lean in fuel cut-off; fault in the sensor interface of the ECM.

Related codes

• P2237O2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)
• P2239O2 Sensor Positive Current Control Circuit High (Bank 1 Sensor 1)
• P2241O2 Sensor Positive Current Control Circuit Low (Bank 2 Sensor 1)
• P0131O2 Sensor Circuit Low Voltage Bank 1 Sensor 1

Sources

• saabwisonline.com: dtc p2237 p2239 p2243 p2251 or p2626
• gsi.ext.gm.com: 2005file14
• static.nhtsa.gov: MC 10237505 0001
• newtonnet.co.uk: fordobd2012

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.