P2240

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

P2240 is a generic OBD-II powertrain diagnostic trouble code: O2 Sensor Positive Current Control Circuit/Open (Bank 2, Sensor 1). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2240
Group
Powertrain
System
powertrain
Severity
Warning (MIL on)
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What P2240 means

P2240 — O2 Sensor Positive Current Control Circuit/Open, Bank 2 Sensor 1 — indicates that the PCM has detected an open circuit or loss of continuity in the positive pump-current (Ip+) control line of the wideband oxygen sensor located upstream of the catalytic converter on Bank 2. Wideband sensors use a dual-cell design: an electrochemical pump cell drives a small current (Ip) through the exhaust gas diffusion gap to maintain a constant oxygen partial pressure at the Nernst measurement cell. The magnitude and polarity of that pump current is the actual lambda signal the PCM reads. The Ip+ line carries the positive side of that controlled current; an open in this conductor means the PCM cannot drive the pump cell and reads no meaningful signal.

The fault is almost always electrical: a broken or corroded wire in the five-wire harness, a damaged connector pin, or a chafed harness section near the exhaust system. Internal failure of the wideband sensor's pump-cell element or the PCM's wideband controller driver IC (the dedicated analog front-end chip used by most OEMs) can also open this circuit. Because the Ip+ and Ip- lines share the same harness and sensor body, P2240 and P2254 sometimes appear together when connector damage is the root cause.

With no valid wideband signal, the PCM runs open-loop or substitutes a default lambda value, causing enrichment or lean-out depending on calibration strategy. Fuel economy and emissions degrade. The MIL illuminates immediately on a Type B fault pathway after two consecutive failed drive cycles.

Common causes

Most-frequently reported root causes when P2240 is logged.

  • 1
    Open circuit (broken wire, corroded pin, or loose connector) in the Ip+ wiring between the PCM and Bank 2 Sensor 1.
  • 2
    Chafed or heat-damaged harness near the exhaust manifold or flex section severing the Ip+ conductor.
  • 3
    Corroded or pushed-back terminal in the wideband sensor connector causing high resistance on the Ip+ pin.
  • 4
    Internal failure of the wideband sensor's pump cell element, opening the Ip+ path within the sensor body.
  • 5
    Failure of the PCM's wideband sensor controller IC (dedicated analog front-end chip) that drives the pump current.
  • 6
    Water intrusion or connector corrosion creating an open between the Ip+ pin and its mating terminal.
  • 7
    Exhaust leak adjacent to the sensor harness causing localised heat damage to the Ip+ wire.

Symptoms drivers notice

Check Engine Light (MIL) illuminated.
Degraded fuel economy from open-loop or default-value fuelling on Bank 2.
Reduced engine performance or hesitation under load as the PCM cannot optimise Bank 2 mixture.
Possible additional codes: P2254 (Ip- open) if both pump-current lines are damaged, or P0141/P0161 heater codes if the harness connector is severely damaged.
No perceptible limp mode in most calibrations, but catalyst protection is reduced.

How to diagnose P2240

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all stored and pending codes; note whether P2254 or heater-circuit codes are present alongside P2240, as co-occurrence points to connector or harness damage rather than an isolated sensor fault.
  2. 2
    With the key off and sensor unplugged, use a multimeter to measure resistance of the Ip+ wire from the PCM connector to the sensor connector; an open (OL) reading confirms a broken wire or corroded pin.
  3. 3
    Inspect the full length of the Bank 2 Sensor 1 harness for heat damage, chafing against the exhaust system, or cracked insulation.
  4. 4
    Examine the wideband sensor connector pins under magnification for corrosion, bending, or pushed-back terminals; clean with contact cleaner and retest.
  5. 5
    If harness and connector are intact, verify PCM-side Ip+ output voltage with a suitable scan tool or oscilloscope while commanding sensor on; no output suggests a PCM driver IC fault.
  6. 6
    Replace the Bank 2 Sensor 1 wideband sensor if the fault is confirmed internal to the sensor body.
  7. 7
    If the PCM driver IC is suspect, consult the OEM calibration data; some PCMs can be reflashed with updated wideband controller firmware before requiring hardware replacement.

Related powertrain codes

Frequently asked questions

What is the Ip+ circuit in a wideband O2 sensor?

In a wideband (LSU-type) sensor the PCM drives a controlled pump current through the sensor's electrochemical pump cell to maintain a precise oxygen partial pressure at the measurement cell. Ip+ is the positive terminal of that pump-current loop. By measuring how much current and in which direction it must push, the PCM derives the exact air/fuel ratio rather than just a rich/lean switch.

Can P2240 appear without any drivability symptoms?

Yes, especially in the early stages. The PCM typically substitutes a default stoichiometric target for the affected bank, so the engine continues running. Fuel economy may drop imperceptibly at first, and the only obvious sign is the MIL. Symptoms become more noticeable during hard acceleration or towing when accurate lambda feedback matters most.

P2240 and P2254 appeared together — is that one fault or two?

Both pump-current lines (Ip+ and Ip-) run through the same five-wire harness and share the same connector. A single point of damage — a crushed connector, a section of harness melted against the exhaust — can open both simultaneously. Diagnose the harness and connector first; if both lines test open, repair the common fault rather than replacing two separate components.

Is PCM replacement necessary for P2240?

Rarely. The vast majority of P2240 faults are external wiring or sensor failures. PCM driver IC failure does occur but is uncommon; it should only be considered after thorough harness and sensor testing confirms no external fault. Some PCMs carry updated wideband controller software that resolves phantom open-circuit detection — check for applicable TSBs before authorising module replacement.

Disabling P2240 in software

RaceTune can permanently disable P2240 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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