P2A83

NOx Sensor Circuit Low Voltage Bank 2 Sensor 1

P2A83 is a generic OBD-II powertrain diagnostic trouble code: NOx Sensor Circuit Low Voltage 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
P2A83
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2A83 means

P2A83 is set when the ECM detects that the signal voltage from the upstream NOx sensor on bank 2 (sensor 1, positioned before the SCR catalyst) has fallen below the minimum expected threshold. This is a circuit-level fault indicating either a short to ground in the signal circuit, an open reference voltage line, or an internal sensor failure causing the output to collapse below the valid operating range.

On V-configuration engines or dual-bank exhaust systems, bank 2 refers to the exhaust path opposite bank 1 (typically the side of the engine not containing cylinder 1). The upstream NOx sensor feeds the ECM with raw exhaust NOx concentration data, which is used to calculate the required DEF injection rate for optimal SCR catalyst operation.

A low-voltage fault on this sensor will cause the ECM to lose bank 2 upstream NOx feedback, potentially defaulting to a fixed or conservative DEF dosing map. This may result in over-dosing (ammonia slip) or under-dosing (reduced NOx conversion), and will prevent the SCR efficiency monitor for bank 2 from completing.

Common causes

Most-frequently reported root causes when P2A83 is logged.

  • 1
    Signal wire shorted to ground between the sensor connector and the ECM.
  • 2
    Open circuit in the sensor reference voltage supply from the ECM.
  • 3
    Failed NOx sensor internal cell producing a collapsed output signal.
  • 4
    Corroded or moisture-ingressed sensor connector causing a partial short to chassis ground.
  • 5
    Damaged wiring harness in an area prone to heat or mechanical abrasion near the exhaust.
  • 6
    Faulty NOx sensor control module (integrated into some sensor assemblies).

Symptoms drivers notice

MIL illuminated on bank 2 exhaust system.
DEF dosing on bank 2 may default to a fixed open-loop strategy.
Possible secondary SCR efficiency fault on bank 2 if dosing is significantly incorrect.
No immediate driveability impact in most operating conditions.

How to diagnose P2A83

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze-frame; note whether any bank 2 heater circuit codes are also present.
  2. 2
    Inspect the NOx sensor 1 bank 2 connector and wiring for visible damage, moisture, or corrosion.
  3. 3
    With the sensor unplugged, measure reference voltage on the ECM-side connector; a missing reference voltage points to an ECM or wiring fault.
  4. 4
    Measure resistance to ground on the signal wire with sensor disconnected to identify a short to ground.
  5. 5
    If wiring checks pass, verify sensor heater resistance to confirm the heater element is intact.
  6. 6
    Substitute a confirmed good sensor and clear codes, then run a complete drive cycle to recheck.
  7. 7
    If the fault returns with a new sensor, trace the fault to the wiring harness or ECM signal circuit.

Vehicles where we've handled P2A83

Platforms in our catalogue with confirmed P2A83 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Is P2A83 a sensor fault or a wiring fault?

It can be either. The code indicates the signal is below the valid range, which is caused by both wiring shorts to ground and internal sensor failures. Wiring should be checked before condemning the sensor.

Can P2A83 occur on a single-bank engine?

P2A83 is a bank 2 code and is only applicable to engines with a dual-bank exhaust configuration. It would not normally be stored on an inline engine with a single SCR path.

Does P2A83 disable DEF dosing entirely?

No. The system typically falls back to open-loop dosing based on engine load and temperature maps rather than shutting off DEF injection completely.

How do I confirm the wiring is the cause and not the sensor?

Disconnect the sensor and back-probe the ECM-side connector for correct reference voltage and no short to ground. If wiring is normal, the sensor is the likely fault.

Disabling P2A83 in software

RaceTune can permanently disable P2A83 — 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.

ECUs with a P2A83 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified 1 software version

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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