Fix P2238: Mechanic’s solutions that WORKED

The P2238: Oxygen (O2) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1) code signals an issue with the oxygen sensor’s pumping current on Bank 1 Sensor 1. This sensor is crucial for optimizing fuel combustion by monitoring the oxygen levels in the exhaust. A fault in this sensor can lead to poor engine performance, increased emissions, and reduced fuel efficiency.

P2238 quick overview

Meaning	P2238: Oxygen (O2) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1)
Is it serious?	This code can be serious as it may affect the vehicle’s fuel efficiency and emissions. It should be addressed promptly.
Possible causes	– Faulty Oxygen Sensor (Bank 1 Sensor 1) – Poor electrical connection at the Oxygen Sensor – Exhaust leaks near the Oxygen Sensor – Faulty Engine Control Module (ECM)
How to diagnose?	Check Oxygen Sensor: Inspect the Bank 1 Sensor 1 Oxygen Sensor for damage or wear. Inspect Wiring and Connectors: Look for damaged wiring or loose connectors at the Oxygen Sensor. Test Sensor Operation: Use a diagnostic scanner to test the sensor’s operation and response time. Check for Exhaust Leaks: Inspect the exhaust system near the sensor for any signs of leaks. Evaluate ECM Function: Consider if the ECM may be faulty and require testing or replacement.

How to fix P2238 – learn from mechanics

I looked into P2238 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Lexus

Vehicle Information: 2002 Lexus ES300 3.0L

Issue + Repair History:

• Originally came in with MIL on and code P2241.
• Replaced bank 2 sensor 1 air-fuel sensor.
• Vehicle returned with intermittent MIL, showing codes P2238 and P2241.

Other OBD2 Codes + Test Results:

• P2238: Oxygen sensor pumping current bank 1 sensor 1
• P2241: Oxygen sensor pumping current bank 2 sensor 1

Suggestions to Fix Issue:

• Verify if the correct air-fuel sensor was used instead of an oxygen sensor.
• Check part numbers for sensors: 89467-33060 (bank 1) and 89467-33050 (bank 2).

Final Fix:

• Replaced the sensor with an air-fuel ratio sensor.
• Cleared codes and returned the vehicle to the customer.

Case #2: Toyota

Vehicle Information: 2004 Toyota Camry XLE 2.4L

Issue + Repair History:

• MIL on with code P2238.
• Replaced bank 2 sensor 1 air-fuel sensor.
• After repair, MIL returned with intermittent codes P2238 and P2241.

Other OBD2 Codes + Test Results:

• P2238: 1/1 H02S pumping current low
• P2241: Oxygen sensor pumping current bank 2 sensor 1

Suggestions to Fix Issue:

• Ensure an air-fuel ratio sensor, not an oxygen sensor, was used.
• Consider ECM reprogramming as per TSB for this issue.
• Check part numbers and compatibility for the sensor used.
• Verify power and ground at heater circuit.

Final Fix:

• Informed customer about potential ECM reprogramming and TSB for code P2238.
• If issue persists, car to be taken to the dealer for ECM flash and possible sensor replacement.

Case #3: Toyota

Vehicle Information: 2003 Toyota 4Runner SR5 4.0L

Issue + Repair History:

• MIL on with codes P0174, P2238, P2241.
• History of A/F sensors being replaced by another shop and dealership.
• Cleaned A/F sensor grounds, swapped A/F sensor relay with dome light relay.
• P0174 code reappeared after initial fixes.

Other OBD2 Codes + Test Results:

• P0174: Lean bank 2
• P2238: B1S1 pumping circuit
• P2241: B2S1 pumping circuit

Suggestions to Fix Issue:

• Check for vacuum leaks on bank 2.
• Consider potential restrictions in the catalytic converter.
• Investigate bank 2 for mechanical issues such as VVT actuator or injector problems.
• Clean or inspect the MAF sensor for issues.
• Examine if there’s an issue with the secondary air pump (if equipped).

Final Fix:

• Replaced bank 2 A/F sensor with an OEM part.
• Issue resolved after A/F sensor replacement. Vehicle running well for 2 weeks after fix.

Case #4: Lexus

Vehicle Information: 2003 Lexus ES300 3.0L

Issue + Repair History:

• MIL on with codes P2238 and P2241.
• A/F sensors replaced according to a TSB.
• Codes returned for both banks after replacements.
• Fuel trims appeared normal during the scan.

Other OBD2 Codes + Test Results:

• P2238: A/F sensor bank 1 sensor 1.
• P2241: A/F sensor bank 2 sensor 1.

Suggestions to Fix Issue:

• Verify correct grounding of the sensors, especially behind the intake.
• Confirm the use of OEM sensors.
• Check the power and ground to the A/F sensors.
• Investigate the ECM’s calibration IDs and potential need for reprogramming.
• Inspect A/F sensor connectors for oil intrusion or terminal issues.

Final Fix:

• Checked the sensor grounds with a headlight and found them to be bright.
• Cleaned battery cables and cleared ECM memory.
• After these actions, the customer has not reported further issues.

Case #5: Toyota

Vehicle Information: 2011 Toyota Corolla 1.8L

Issue + Repair History:

• MIL on with codes P0102, P0113, P2238, and P0010.
• Scanners used (Verus Edge, Autoenginuity, Toyota Techstream) could not clear the codes.

Other OBD2 Codes + Test Results:

• P0102: MAF Circuit Low
• P0113: Intake Air Temperature Circuit High
• P2238: O2 Sensor Positive Current Control Circuit Low
• P0010: Camshaft Position Actuator Circuit

Suggestions to Fix Issue:

• Use OEM parts for replacements.
• Check MAF sensor wiring and connections.
• Ensure proper calibration of ECM.
• Verify power and ground to the sensors.
• Check for enabling criteria issues related to the DTCs.
• Test MAF sensor signal directly at ECM.

Final Fix:

• Replaced MAF sensor and both A/F sensors with OEM parts

Advice	Brief Description of Diagnostic Step
Use OEM Parts	Replace sensors with original equipment manufacturer parts.
Check Grounds	Verify the grounding of sensors, especially behind the intake.
Verify Sensor Wiring	Inspect the wiring and connections of the affected sensor.
ECM Calibration	Check if the ECM requires updating or recalibration.
Check for Vacuum Leaks	Inspect for any leaks that might affect sensor readings.
Test Sensor Signal at ECM	Verify the sensor’s signal directly at the ECM for accuracy.
Check for Exhaust Leaks	Inspect the exhaust system for any leaks that could affect readings.