P24D0

NOx Sensor Circuit High Voltage Bank 1 Sensor 2

P24D0 is a generic OBD-II powertrain diagnostic trouble code: NOx Sensor Circuit High Voltage Bank 1 Sensor 2. 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
P24D0
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
Need P24D0 disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P24D0 means

P24D0 is set when the PCM detects that the signal voltage from the downstream NOx sensor (Bank 1, Sensor 2) is above the maximum expected threshold. The downstream NOx sensor is positioned after the SCR catalyst and measures post-catalyst NOx concentration, which is used to evaluate SCR conversion efficiency and adjust reductant dosing.

A persistently high signal voltage from this sensor indicates that the PCM cannot accurately assess catalyst-out NOx levels. This compromises the closed-loop SCR control strategy and may cause the system to under-dose reductant, resulting in elevated tailpipe emissions. The fault can arise from a short to voltage in the signal wiring, a defective sensor, or a fault in the sensor control module.

The MIL is illuminated when the fault is confirmed. Because the downstream sensor is critical for verifying SCR system performance and meeting OBD-II monitoring requirements, this code will generally also trigger an SCR system monitoring failure. Diagnosis should begin with the electrical circuit before condemning the sensor or module.

Common causes

Most-frequently reported root causes when P24D0 is logged.

  • 1
    Short circuit to battery voltage in the downstream NOx sensor signal wire.
  • 2
    Failed downstream NOx sensor with internally elevated output.
  • 3
    Faulty NOx sensor control module producing incorrect reference or signal voltage.
  • 4
    Damaged wiring harness causing a signal wire to contact a voltage source.
  • 5
    Corroded connector pins creating unintended voltage paths.
  • 6
    Incorrect replacement sensor with incompatible signal range installed.
  • 7
    PCM calibration or software fault misinterpreting sensor output.

Symptoms drivers notice

MIL illuminated.
SCR system unable to verify catalyst conversion efficiency.
Possible SCR catalyst efficiency fault codes stored concurrently.
Scan tool showing downstream NOx sensor voltage above normal range.
Potential increase in tailpipe NOx emissions.

How to diagnose P24D0

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record all DTCs and freeze frame data.
  2. 2
    Check live downstream NOx sensor voltage and compare to manufacturer specification.
  3. 3
    Inspect the signal circuit wiring from the sensor to the control module for shorts to voltage.
  4. 4
    Disconnect the sensor and re-measure the signal wire voltage to isolate a harness fault from a sensor fault.
  5. 5
    Inspect the sensor connector for corrosion, moisture, or terminal damage.
  6. 6
    If wiring is intact, replace the downstream NOx sensor and retest.
  7. 7
    Clear codes and perform a drive cycle to confirm resolution.

Vehicles where we've handled P24D0

Platforms in our catalogue with confirmed P24D0 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What is the difference between P24D0 and P24B3?

Both are high-voltage NOx sensor faults, but P24B3 affects Sensor 1 (upstream of the SCR catalyst) and P24D0 affects Sensor 2 (downstream of the SCR catalyst).

Can a failing SCR catalyst cause P24D0?

A failing catalyst would affect the NOx concentration reading, but P24D0 is specifically a circuit voltage fault. A high catalyst-out NOx reading due to a failed catalyst would more likely set a catalyst efficiency code rather than P24D0.

Is the downstream sensor more exposed to damage than the upstream sensor?

The downstream sensor operates in lower-temperature, post-catalyst exhaust which is less thermally extreme, but it is exposed to ammonia slip and any unreacted DEF, which can contaminate the sensing element over time.

Will this code resolve on its own?

No. A circuit short or sensor failure requires physical repair. The code will continue to set until the root cause is corrected.

Disabling P24D0 in software

RaceTune can permanently disable P24D0 — 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 P24D0 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
  • Bosch EDC17CP09 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.

Got P24D0 in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file