P2240 O2 Sensor Positive Current Control Circuit/Open (Bank 2 Sensor 1)

P2240 is a generic OBD-II diagnostic trouble code that indicates the Engine Control Module (ECM) has detected an open circuit in the Oxygen (O2) Sensor Positive Current Control Circuit for Bank 2 Sensor 1.

In simple terms, the ECM has determined that the positive current control circuit of the upstream oxygen sensor on Bank 2 has lost electrical continuity. Without this circuit functioning correctly, the oxygen sensor cannot accurately monitor the air-fuel ratio, causing the ECM to lose an important source of fuel control data. This may result in poor engine performance, increased fuel consumption, and higher exhaust emissions.

Bank 2 Sensor 1 refers to the upstream oxygen sensor located before the catalytic converter on the engine bank that does not contain cylinder number one.

Modern wideband oxygen sensors, also known as Air/Fuel Ratio (A/F) sensors, rely on multiple electrical circuits, including a positive current control circuit that regulates the sensor's internal pump cell. When this circuit becomes open or disconnected, the ECM stores diagnostic trouble code P2240 and usually illuminates the Check Engine Light.

What Does P2240 Mean?

Wideband oxygen sensors are significantly more advanced than traditional narrowband oxygen sensors.

They continuously monitor the oxygen content in the exhaust gases and allow the ECM to make precise fuel adjustments.

The system typically includes:

• Upstream oxygen sensor (Bank 2 Sensor 1)

• Positive current control circuit

• Negative current control circuit

• Reference voltage circuit

• Signal circuit

• Oxygen sensor heater

• Wiring harness

• Electrical connectors

• Engine Control Module (ECM)

The ECM uses this information to:

• Control fuel injection

• Maintain the correct air-fuel ratio

• Improve fuel economy

• Reduce exhaust emissions

• Protect the catalytic converter

The code description contains several important meanings:

O2 Sensor

The upstream oxygen sensor measures oxygen levels before the catalytic converter.

Positive Current Control Circuit

This circuit controls the positive pump current required for proper operation of the wideband oxygen sensor.

Open

The ECM has detected a complete interruption or loss of continuity in the circuit.

Possible causes include:

• Broken wiring

• Disconnected connector

• Internal sensor failure

• Wiring harness damage

• ECM driver failure

Symptoms of P2240

The severity of symptoms depends on how much the circuit failure affects sensor operation.

Common symptoms include:

Check Engine Light

The Check Engine Light usually illuminates immediately after the fault is detected.

Poor fuel economy

Fuel consumption may increase because the ECM cannot accurately control the air-fuel mixture.

Rough idle

The engine may idle unevenly or feel unstable.

Engine hesitation

Acceleration may become sluggish or inconsistent.

Reduced engine performance

Engine power may decrease due to incorrect fuel delivery.

Hard starting

Some vehicles may require longer cranking before starting.

Failed emissions inspection

Improper fuel control may increase exhaust emissions.

Common Causes of P2240

Several problems can cause an O2 Sensor Positive Current Control Circuit/Open condition.

Faulty oxygen sensor

A defective Bank 2 Sensor 1 oxygen sensor is one of the most common causes.

Possible failures include:

• Internal open circuit

• Pump cell failure

• Heat damage

• Internal electrical failure

Broken wiring

A damaged wire may interrupt the positive current control circuit.

Possible causes include:

• Wiring fatigue

• Rodent damage

• Mechanical damage

• Previous electrical repairs

Loose or disconnected connector

A partially disconnected connector may interrupt current flow.

Possible issues include:

• Loose connector

• Broken locking tab

• Bent connector pins

• Improper installation

Corroded terminals

Corrosion may prevent electrical continuity.

Possible causes include:

• Moisture intrusion

• Oxidation

• Road salt exposure

Damaged wiring harness

The wiring harness may become damaged by:

• Engine heat

• Vibration

• Road debris

• Contact with moving engine components

Previous wiring modifications

Improper aftermarket electrical repairs may create an open circuit.

Faulty ECM

Although uncommon, the ECM may fail to control the positive current circuit correctly.

Possible causes include:

• Internal driver failure

• Software malfunction

Vehicles Commonly Affected by P2240

P2240 may occur on many vehicles equipped with wideband oxygen sensors.

Common examples include:

• Toyota

• Lexus

• Honda

• Acura

• Nissan

• Infiniti

• Ford

• Chevrolet

• GMC

• BMW

• Mercedes-Benz

• Audi

• Volkswagen

• Subaru

• Hyundai

• Kia

The exact diagnostic procedure depends on the manufacturer.

How Is P2240 Diagnosed?

Proper diagnosis requires inspecting the oxygen sensor and the complete positive current control circuit.

Check for additional trouble codes

A professional scan tool should check for related codes such as:

• Air/Fuel Ratio Sensor codes

• Oxygen sensor heater codes

• Fuel trim codes

• Catalyst efficiency codes

• Misfire codes

Related trouble codes often help narrow down the root cause.

Inspect the oxygen sensor

Technicians should inspect Bank 2 Sensor 1 for:

• Physical damage

• Heat damage

• Contamination

• Proper installation

Inspect wiring and connectors

The complete circuit should be inspected for:

• Broken wires

• Loose connectors

• Corrosion

• Heat damage

• Wiring harness damage

Test circuit continuity

Using a digital multimeter, technicians should verify:

• Circuit continuity

• Connector condition

• Wiring resistance

• Ground integrity

Monitor live sensor data

Using a professional scan tool, technicians should monitor:

• Air-fuel ratio readings

• Oxygen sensor activity

• Fuel trim values

• Sensor response speed

No activity or fixed readings often indicate an open circuit.

Inspect the exhaust system

Inspect for exhaust leaks near the oxygen sensor that could affect sensor operation.

How to Fix P2240

The proper repair depends on the source of the open circuit.

Common repairs include:

Replace the oxygen sensor

Replace Bank 2 Sensor 1 if testing confirms internal sensor failure.

Repair damaged wiring

Electrical repairs may include:

• Replacing broken wires

• Repairing open circuits

• Restoring damaged insulation

Repair connector problems

Repairs may include:

• Cleaning corroded terminals

• Replacing damaged connectors

• Securing loose electrical connections

Repair wiring harness damage

Damaged harness sections should be repaired or replaced.

Repair ground connections

Ground points should be cleaned and tightened if necessary.

Repair ECM-related faults

Rarely, ECM software updates or replacement may be required.

After repairs:

1. Clear the diagnostic trouble code.

2. Start the engine.

3. Monitor live oxygen sensor data.

4. Perform a complete road test.

5. Confirm that the code does not return.

Can You Drive With P2240?

Driving with P2240 is generally possible for a short period, but it is not recommended.

Possible consequences include:

• Increased fuel consumption

• Reduced engine performance

• Higher exhaust emissions

• Catalytic converter damage

• Failed emissions inspection

Prompt diagnosis and repair help prevent more extensive engine and emissions system damage.

Is P2240 a Serious Code?

P2240 is generally considered a moderate to serious diagnostic trouble code.

Although the vehicle may continue to run, an open positive current control circuit prevents the upstream oxygen sensor from accurately measuring the air-fuel ratio.

Ignoring the issue may eventually lead to:

• Poor fuel economy

• Increased emissions

• Reduced engine performance

• Premature catalytic converter failure

Early diagnosis and repair help avoid more extensive repairs.

How to Prevent P2240

Routine maintenance can reduce the likelihood of oxygen sensor circuit failures.

Recommended practices include:

• Inspect oxygen sensor wiring during scheduled maintenance.

• Repair damaged wiring immediately.

• Keep electrical connectors clean and dry.

• Repair exhaust leaks promptly.

• Avoid improper aftermarket electrical modifications.

• Use high-quality replacement oxygen sensors.

• Investigate Check Engine Light warnings as soon as they appear.

Final Thoughts

P2240 O2 Sensor Positive Current Control Circuit/Open (Bank 2 Sensor 1) indicates that the ECM has detected a loss of electrical continuity in the positive current control circuit of the upstream oxygen sensor on Bank 2.

The most common causes include a faulty oxygen sensor, broken wiring, damaged wiring harnesses, loose or corroded connectors, previous wiring modifications, or, in rare cases, an ECM malfunction.

A thorough inspection of the oxygen sensor, positive current control circuit, wiring, connectors, and related electrical components is essential to restore accurate air-fuel ratio monitoring, improve engine performance, reduce emissions, and protect the catalytic converter from long-term damage.