P2237

Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1

P2237 is a generic OBD-II powertrain diagnostic trouble code: Sensor Positive Current Control Circuit/Open Bank 1 Sensor 1. It is logged by the engine control unit when the scr/adblue monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2237
Group
Powertrain
System
SCR/AdBlue
Severity
high
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What P2237 means

Code P2237 is specific to vehicles equipped with a wideband (broadband/linear) air-fuel ratio (AFR) sensor on the upstream position of Bank 1. Unlike a conventional narrowband zirconia sensor that produces a simple high/low voltage signal, a wideband sensor uses multiple internal electrochemical cells to measure lambda continuously across a wide AFR range. The key internal components are: the Nernst cell (the classical electrochemical element that measures oxygen partial pressure), the pumping cell (which actively pumps oxygen in or out to keep the Nernst cell at a fixed reference voltage), and a dedicated positive current control circuit through which the ECU supplies and measures the pump current. The magnitude and direction of that pump current is the actual lambda signal. P2237 is stored when the PCM detects an open circuit or complete loss of signal on this positive current control line.

With the positive current circuit open, the ECU cannot control or measure pump current, so the lambda signal collapses. The PCM loses closed-loop fuel control capability and reverts to open-loop operation based on pre-programmed fuel maps, typically resulting in rough running, elevated emissions, and poor drivability. The sensor's internal circuit board or the wiring between the sensor and the ECU is the most common point of failure — the positive current wire is a low-voltage control line that is particularly sensitive to corrosion, chafing, or connector damage.

Diagnosis must distinguish between a wiring/connector fault and an internal sensor failure. If the circuit tests out correctly (correct resistance, no open or short), the sensor itself has failed internally and must be replaced. Because wideband sensors are more complex and expensive than narrowband types, confirming the wiring is sound before replacing the sensor is important.

Common causes

Most-frequently reported root causes when P2237 is logged.

  • 1
    Internal failure of the wideband O2 sensor's positive current control circuit (most common)
  • 2
    Corroded, bent, or backed-out connector pins at the sensor harness plug
  • 3
    Chafed or broken positive current control wire in the harness (heat, rubbing on exhaust)
  • 4
    Water or moisture intrusion into the sensor connector shorting the low-voltage circuit
  • 5
    Damaged sensor pigtail wiring due to poor routing or physical impact
  • 6
    Failed or missing sensor heater causing thermal shock damage to internal cells
  • 7
    Blown fuse or open relay supplying the sensor heater (can cascade to cell damage)
  • 8
    PCM internal fault — open or damaged current-sense circuit (rare)

Symptoms drivers notice

MIL (Check Engine Light) illuminated
Engine enters open-loop fuel control — poor fuel economy
Rough idle and hesitation under load
Reduced engine power
Failed emissions test (lambda out of bounds)
Possible companion codes P2238 (circuit low) or heater codes (P0135)

How to diagnose P2237

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored DTCs and freeze-frame data; note any companion heater codes (P0135) or other wideband sensor codes that may indicate a wider circuit or sensor failure
  2. 2
    Inspect the wideband sensor connector and the wiring harness from the sensor back to the ECU for chafing, corrosion, moisture, melted insulation, or bent pins
  3. 3
    With the ignition off, use a DVOM to measure resistance on the positive current control wire between the sensor connector and the PCM connector; an open reading (OL/infinite) confirms a broken wire
  4. 4
    Check for a short to ground on the same wire; resistance to chassis ground should be infinite (OL) on an open-circuit harness
  5. 5
    Verify sensor heater supply voltage and ground integrity; a failed heater can cause thermal damage to the internal cells and mimic a circuit fault
  6. 6
    If wiring tests pass, compare the sensor's internal resistance between the positive current terminals against the sensor manufacturer's specification; out-of-spec reading indicates internal sensor failure
  7. 7
    Replace the wideband sensor if the harness is sound and internal resistance is out of specification; clear codes and complete a full drive cycle to confirm the repair

Related powertrain codes

Frequently asked questions

What is the positive current control circuit on a wideband sensor?

Wideband sensors measure AFR by actively pumping oxygen ions through an internal pumping cell. The ECU controls this by supplying a variable current through the positive current control wire.

Can I drive with P2237?

The engine will revert to open-loop fuel control, running on fixed fuel maps without sensor feedback. Short trips may be acceptable, but fuel economy and emissions will suffer significantly.

P2237 is an 'open circuit' code — what does that mean?

An open circuit means there is a break in the positive current control wire path, so no current can flow between the ECU and the sensor.

Is P2237 always a failed sensor?

Not always. The break can be anywhere in the harness from the sensor connector to the PCM pin.

Disabling P2237 in software

RaceTune can permanently disable P2237 — 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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