P2585

Reductant Temperature Sensor Circuit High

P2585 is a generic OBD-II powertrain diagnostic trouble code: Reductant Temperature 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
P2585
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2585 means

P2585 is the high-side companion to P2583 and is stored when the DEF temperature sensor signal voltage exceeds the maximum calibrated threshold. For NTC thermistor sensors, a circuit high condition typically results from an open circuit in the sensor element or wiring, which causes the signal to float high toward the reference voltage rather than being pulled down by the thermistor resistance.

Less commonly, a short to the 5V reference voltage on the signal wire can also cause a high reading. Because the sensor is used to protect the DEF system from operating in temperature extremes and to control the DEF heater, a faulty high reading may prevent heater activation in cold conditions, risking DEF freezing and SCR system disablement.

Diagnosis starts with connector inspection and a resistance measurement across the sensor element. An open-circuit sensor will show infinite resistance regardless of temperature, making it straightforward to distinguish from a wiring fault through a simple resistance test at the connector and then at the sensor terminals directly.

Common causes

Most-frequently reported root causes when P2585 is logged.

  • 1
    Open circuit in the NTC temperature sensor element.
  • 2
    Broken or disconnected sensor signal wire causing the line to float high.
  • 3
    Short to the 5V reference wire on the signal line.
  • 4
    Corroded sensor connector with high-resistance contact increasing apparent voltage.
  • 5
    Water or DEF ingress causing open circuit at the sensor connector.
  • 6
    Damaged wiring harness with a broken conductor near the DEF module.
  • 7
    Faulty SCR control module input circuit.

Symptoms drivers notice

MIL or emissions warning lamp illuminated.
DEF temperature reads implausibly high or at a fixed maximum on a scan tool.
DEF heater may fail to activate in cold conditions, risking DEF freezing.
SCR system may restrict or alter dosing based on erroneous temperature data.
No immediate driveability impact but cold-weather SCR performance may be affected.

How to diagnose P2585

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs; note any heater, SCR performance, or DEF freezing codes alongside P2585.
  2. 2
    Compare live DEF temperature reading to ambient temperature for plausibility.
  3. 3
    Inspect the sensor connector and harness for open circuits, corrosion, and physical damage.
  4. 4
    With the sensor connected, measure signal voltage; a reading near the reference voltage suggests an open circuit.
  5. 5
    Unplug the sensor and measure resistance across the sensor terminals; an open-circuit sensor will show infinite resistance.
  6. 6
    Check the signal wire continuity from the sensor connector back to the control module.
  7. 7
    Replace the sensor if found open-circuit; repair wiring if continuity is broken in the harness.

Vehicles where we've handled P2585

Platforms in our catalogue with confirmed P2585 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Will P2585 cause DEF to freeze in winter?

If the heater does not activate due to a false high-temperature reading, DEF can freeze at temperatures below approximately -11 degrees Celsius, disabling the SCR system.

Can I distinguish P2585 from P2583 without a scan tool?

Not reliably; a scan tool showing an out-of-range temperature reading is the most direct indicator. P2585 will show an implausibly high value and P2583 an implausibly low value.

Is P2585 always caused by a bad sensor?

No; an open circuit anywhere in the signal wire between the sensor and the module will produce the same circuit high result, so wiring diagnosis is essential before replacing the sensor.

Does P2585 affect DEF dosing?

It can, because the control module uses temperature data to correct injection quantity. An erroneous reading may cause minor dosing inaccuracies, affecting SCR conversion efficiency.

Disabling P2585 in software

RaceTune can permanently disable P2585 — 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 P2585 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.

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