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

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK You can usually drive for a while: the engine runs on a default fuel strategy, which costs you fuel and emissions. Fix it soon — prolonged driving with a bad O2 sensor can overheat and damage the catalytic converter.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P2240 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the oxygen sensor circuit for damage, corrosion, chafing or poor contact.
Subsystem check Watch the sensor voltage in live data: a healthy upstream sensor switches rapidly between roughly 0.1 and 0.9 V.
Subsystem check Measure heater resistance on the sensor connector and check the heater fuse and relay.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2240 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P2240 (parts and labor, USD, independent shop rates): Replace the oxygen sensor: $150–$450; Repair sensor wiring: $80–$250; Fix an exhaust leak near the sensor: $100–$300. Overall, fixing P2240 usually costs between $80 and $450. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How do I diagnose P2240 myself?

Start with a scan: confirm P2240, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the oxygen sensor circuit, and verify the suspect component against live data before buying parts.

What does OBD2 code P2240 mean?

O2 Sensor Positive Current Control Circuit/Open Bank 2 Sensor 1 (P2240): a powertrain (engine/transmission) fault affecting the oxygen sensor circuit. The car is usually drivable while you plan the repair. Most often caused by aged or contaminated oxygen sensor, exhaust leak near the sensor, blown sensor heater fuse.

Will P2240 clear itself?

Sometimes P2240 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of P2240?

The most common causes are: aged or contaminated oxygen sensor, exhaust leak near the sensor, blown sensor heater fuse.

Is it safe to drive with P2240?

You can usually drive for a while: the engine runs on a default fuel strategy, which costs you fuel and emissions. Fix it soon — prolonged driving with a bad O2 sensor can overheat and damage the catalytic converter.

What does P2240 mean?

Seeing P2240 on your scanner? The control unit has caught the oxygen sensor circuit operating outside its calibrated window. The formal description is “O2 Sensor Positive Current Control Circuit/Open Bank 2 Sensor 1”, and the code is grouped under powertrain (engine/transmission) faults.

In this definition, “Bank 2” is the side of the engine opposite to cylinder 1 and “Sensor 1” is the upstream (before the catalytic converter) sensor. Mixing up banks and sensor positions is the most common DIY mistake with this code — verify the physical location before replacing anything.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores P2240 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes P2240?

aged or contaminated oxygen sensor
ECM signal circuit fault
damaged sensor wiring or connector
blown sensor heater fuse
exhaust leak near the sensor
oil or coolant contamination of the sensor tip

Common symptoms of P2240

failed emissions test
sluggish throttle response
Check Engine Light on
increased fuel consumption
rough idle

How to diagnose P2240

Connect an OBD2 scanner, confirm P2240 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Visually inspect the wiring harness and connectors related to the oxygen sensor circuit for damage, corrosion, chafing or poor contact.
Watch the sensor voltage in live data: a healthy upstream sensor switches rapidly between roughly 0.1 and 0.9 V.
Measure heater resistance on the sensor connector and check the heater fuse and relay.
Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2240 does not return.

How to fix P2240

Start with the cheapest and most common causes before replacing expensive parts:

Replace the oxygen sensor — $150–$450
Repair sensor wiring — $80–$250
Fix an exhaust leak near the sensor — $100–$300

How much does it cost to fix P2240?

Repair cost depends on which component actually failed. Typical scenarios for P2240 (parts and labor, USD, independent shop rates):

Replace the oxygen sensor: $150–$450
Repair sensor wiring: $80–$250
Fix an exhaust leak near the sensor: $100–$300

Overall, fixing P2240 usually costs between $80 and $450. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.