P24C7

Reductant Quality Sensor Circuit High

P24C7 is a generic OBD-II powertrain diagnostic trouble code: Reductant Quality Sensor Circuit High. 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
P24C7
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P24C7 means

P24C7 is stored when the ECM detects that the reductant quality sensor signal voltage is above the expected maximum threshold. The quality sensor (often a combined concentration and temperature sensor) monitors the urea concentration in the DEF tank to confirm that it meets the required 32.5% urea solution specification. A circuit-high condition indicates the sensor output voltage is stuck high or is being pulled to a voltage above the normal operating range.

Possible causes include a short to voltage on the signal wire, a failed sensor with a high-side output, loss of sensor ground, or a faulty control module input. When this code is active, the ECM may assume the DEF quality is unknown or unacceptable and log supplementary efficiency or quality fault codes, potentially restricting SCR operation.

Diagnosis should start with a visual inspection of the quality sensor and its connector, which typically sits on or inside the DEF tank. The sensor signal voltage should be measured with a digital multimeter or oscilloscope against manufacturer specifications while the sensor is connected and disconnected to isolate a wiring fault from a sensor fault. Verify sensor ground and reference voltage before condemning the sensor or module.

Common causes

Most-frequently reported root causes when P24C7 is logged.

  • 1
    Short to battery voltage on the quality sensor signal wire.
  • 2
    Loss of sensor ground reference causing signal to appear high.
  • 3
    Failed reductant quality sensor with internally stuck high output.
  • 4
    Damaged wiring harness causing signal line contact with a B+ source.
  • 5
    Water or DEF intrusion into the sensor connector causing leakage current.
  • 6
    Faulty ECM or reductant control module input circuit.

Symptoms drivers notice

MIL illuminated.
Possible DEF quality warning on the driver information display.
SCR system may reduce or suspend dosing if quality is deemed unverifiable.
Additional reductant system codes may be stored simultaneously.

How to diagnose P24C7

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record all active and pending codes along with freeze frame data.
  2. 2
    Inspect the DEF quality sensor connector for corrosion, DEF crystallization, or spread pins.
  3. 3
    Measure reference voltage and ground at the sensor connector with the ignition on.
  4. 4
    Back-probe the signal wire and measure voltage; compare to the expected range in the service data.
  5. 5
    Disconnect the sensor and measure signal wire voltage; if still high, a short to voltage exists in the harness.
  6. 6
    Measure sensor resistance or output voltage in isolation to verify sensor integrity.
  7. 7
    Replace the sensor if wiring and module checks pass, or repair the harness if a short is found.

Vehicles where we've handled P24C7

Platforms in our catalogue with confirmed P24C7 coverage.

AUDI A4 20D
BMW 320D
2016

Related powertrain codes

Frequently asked questions

Could using the wrong DEF fluid cause P24C7?

Wrong fluid concentration or contaminated DEF would more commonly cause a plausibility or quality rationality code, but if it damages the sensor over time, a circuit fault is possible.

Is the quality sensor the same as the level sensor?

No. They may be combined in one assembly on some vehicles, but they measure different properties. P24C7 specifically targets the quality (concentration) measurement circuit.

Can I clear this code and pass an emissions test?

Clearing the code sets monitors incomplete; the vehicle will fail an OBD readiness check until the monitors run and pass.

Does this code mean my DEF is bad?

P24C7 is an electrical circuit fault. The sensor may not be reading correctly, so a fluid quality conclusion cannot be drawn from this code alone.

Disabling P24C7 in software

RaceTune can permanently disable P24C7 — 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 P24C7 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 EDC17C74 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.

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