P200D

Diesel Particulate Filter Over Temperature Bank 2

P200D is a generic OBD-II powertrain diagnostic trouble code: Diesel Particulate Filter Over Temperature Bank 2. It is logged by the engine control unit when the dpf monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P200D
Group
Powertrain
System
DPF
Severity
Warning (MIL on)
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What P200D means

P200D is set when the PCM or diesel after-treatment control module detects that the voltage on the reductant (DEF/AdBlue) injection air purge control circuit is lower than expected. Selective catalytic reduction (SCR) systems on some platforms use compressed air to atomize or purge the urea dosing injector; the air purge valve is commanded to open after an engine-off event to clear residual DEF from the injector tip and supply line, preventing crystallization that would block the nozzle.

A low circuit condition typically indicates a short to ground in the wiring between the control module and the purge valve solenoid, a failed solenoid with lower-than-normal winding resistance, or a wiring harness damaged in the area exposed to exhaust heat or road debris under the vehicle. Because the purge function is critical to preventing injector blockage, the SCR system may inhibit DEF dosing to protect the injector, which will cause NOx emissions to rise and eventually trigger additional SCR efficiency fault codes.

Repair requires resolving the electrical fault before assessing whether the injector itself has been damaged by crystallized urea. On some platforms the DEF injector and purge valve are a combined assembly.

Common causes

Most-frequently reported root causes when P200D is logged.

  • 1
    Short to ground in the wiring harness between the control module and the air purge solenoid.
  • 2
    Air purge solenoid winding shorted internally, drawing excessive current and pulling circuit voltage low.
  • 3
    Damaged connector at the DEF injector or purge valve assembly due to heat or physical impact.
  • 4
    Chafed wiring routed near exhaust components or chassis members causing an intermittent ground short.
  • 5
    Control module output driver fault causing the pin to be pulled low even when not commanded.
  • 6
    Corrosion at the purge valve connector bridging signal and ground pins.
  • 7
    Incorrect replacement solenoid with wrong impedance installed.

Symptoms drivers notice

MIL and/or SCR warning lamp illuminated.
DEF dosing may be suspended, causing rising NOx emissions.
Possible urea crystallization at the injector tip if purge has been non-functional for an extended period.
Subsequent SCR catalyst efficiency codes may accompany P200D.
No noticeable drivability change unless SCR-related limp mode is also triggered.

How to diagnose P200D

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record all active and pending DTCs; note any companion SCR efficiency or NOx sensor codes.
  2. 2
    Inspect the DEF injector and air purge valve wiring harness under the vehicle for heat damage, chafing, or impact damage.
  3. 3
    Disconnect the purge valve connector and measure resistance of the solenoid winding; compare to specification.
  4. 4
    With the connector unplugged, measure voltage on the control wire at the harness side relative to ground to check for a short to ground.
  5. 5
    Repair any wiring shorts or connector damage found before reconnecting.
  6. 6
    After electrical repair, command the purge valve with a scan tool and confirm correct circuit response.
  7. 7
    Inspect the DEF injector tip for urea crystallization and clean or replace if blocked.

Related powertrain codes

Frequently asked questions

What happens if I ignore P200D?

Without the air purge function, the DEF injector tip can become blocked with crystallized urea. The SCR system will eventually disable DEF dosing, causing NOx exceedances and additional fault codes.

Can P200D be caused by a bad DEF pump rather than the purge valve?

P200D is specific to the air purge control circuit. DEF pump faults generate their own separate codes. However, it is worth inspecting the entire dosing assembly wiring harness as it passes through the same area.

Is the air purge valve the same as the DEF injector?

On some systems they are integrated into a single assembly; on others they are separate components. Consult the service information for the specific platform.

Will clearing P200D and driving resolve the issue if there is no visible wiring damage?

You can attempt a clear and retest cycle, but if the short to ground is present, the code will return quickly. Thorough wiring inspection under the vehicle is needed.

Disabling P200D in software

RaceTune can permanently disable P200D — 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.

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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