P040D

Gas Recirculation Temperature Sensor A Circuit High

P040D is a generic OBD-II powertrain diagnostic trouble code: Gas Recirculation Temperature Sensor A Circuit High. It is logged by the engine control unit when the egr monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P040D
Group
Powertrain
System
EGR
Severity
Warning (MIL on)
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What P040D means

P040D is a SAE generic powertrain fault code defined as Exhaust Gas Recirculation (EGR) Temperature Sensor 'A' Circuit/Open. It is set by the PCM/ECM when it detects that the signal from the EGR temperature sensor 'A' is absent or has fallen outside the expected operating range in a way consistent with an open circuit condition. The EGR temperature sensor is a thermistor mounted in the EGR gas path; it provides real-time feedback that the ECM uses to verify EGR flow and to protect downstream components from overtemperature.

An open circuit can originate anywhere in the sensor loop: the sensor itself, the wiring harness between sensor and ECM, or the ECM connector pins. Because the ECM can no longer confirm actual EGR gas temperature, it loses the ability to precisely modulate EGR valve position and may disable EGR operation entirely as a protective measure.

P040D belongs to the P040x family of EGR temperature sensor codes. It is most commonly encountered on diesel engines and on GDI petrol engines with low-pressure EGR systems.

Common causes

Most-frequently reported root causes when P040D is logged.

  • 1
    Open circuit or broken wire in the EGR temperature sensor signal or ground circuit
  • 2
    Faulty EGR temperature sensor 'A' (thermistor element failure — internal open)
  • 3
    Corroded, backed-out, or damaged connector pins at the EGR sensor or ECM connector
  • 4
    Chafed or heat-damaged wiring harness routed near the exhaust or EGR cooler
  • 5
    High-resistance short to voltage on the signal wire causing the ECM to read an open
  • 6
    Failed or damaged EGR cooler causing sensor exposure to extreme temperatures
  • 7
    ECM pin damage or internal ECM fault (rare)

Symptoms drivers notice

Illuminated MIL (Check Engine light)
Increased fuel consumption due to EGR system operating open-loop or being disabled
Elevated NOx emissions (vehicle may fail emissions testing)
Rough idle or slight hesitation under load if EGR is disabled
Possible limp mode or power reduction on diesel vehicles with strict EGR monitoring
No noticeable drivability change in mild cases where EGR is only partially disabled

How to diagnose P040D

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored DTCs and freeze-frame data; note any related EGR valve codes
  2. 2
    Inspect the EGR temperature sensor connector and harness for visible damage, heat cracking, corrosion
  3. 3
    With the ignition on (engine off), measure the signal wire voltage between the sensor connector and ground
  4. 4
    Measure sensor resistance across the thermistor terminals at a known temperature
  5. 5
    Perform a wiring continuity check from the sensor connector back to the ECM connector
  6. 6
    Clear the DTC, perform a drive cycle that enables the EGR monitor, and confirm whether the code resets
  7. 7
    If all wiring and sensor checks pass, consult manufacturer live-data specifications

Vehicles where we've handled P040D

Platforms in our catalogue with confirmed P040D coverage.

BMW X5
2018–2019
BMW 530XD
2017
AUDI A4 20D
BMW 320D
2016
AUDI A6
2015
AUDI A7 30D
BMW 530XD 30D
AUDI A6 30D
2015

Related powertrain codes

Frequently asked questions

Can I drive with code P040D active?

Short-term driving is generally safe because P040D alone does not usually cause an immediate mechanical failure. However, the EGR system may be disabled, raising NOx emissions and potentially worsening fuel economy.

Is P040D the same as P040A or P040B?

No. P040A indicates the EGR temperature sensor 'A' circuit is reading low, P040B indicates it is reading high, and P040D specifically flags an open circuit condition where the ECM receives no valid signal at all.

How do I tell if the sensor or the wiring is at fault?

Disconnect the sensor connector and measure resistance across the sensor's thermistor terminals. If you read open-circuit, the sensor has failed internally. If resistance is within specification, check wire continuity and voltage back to the ECM.

Will replacing the EGR temperature sensor always fix P040D?

Not always. An open circuit in the wiring harness or a corroded connector is equally likely, especially on older vehicles. Always perform a full circuit check before replacing parts.

Disabling P040D in software

RaceTune can permanently disable P040D — 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 P040D 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 EDC17CP57 verified 2 software versions
  • Bosch EDC17C50 verified 1 software version
  • Bosch EDC17C56 verified 1 software version
  • Bosch EDC17C66 verified 1 software version
  • Bosch EDC17C74 verified 1 software version
  • Bosch EDC17CP44 verified 1 software version
  • Bosch MD1CP002 verified 1 software version
  • Bosch MD1CS001 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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