P206B

Reductant Pump 'B' Control Performance

P206B is a generic OBD-II powertrain diagnostic trouble code: Reductant Pump 'B' Control Performance. 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
P206B
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P206B means

P206B is an SAE generic powertrain code defined as Reductant Pump 'B' Control Performance. It is set by the Engine Control Module (ECM) or Selective Catalytic Reduction (SCR) control module when the output of the secondary ('B') Diesel Exhaust Fluid (DEF/AdBlue) reductant pump deviates from its commanded target beyond a calibrated threshold. The 'B' designation refers to the second pump circuit — common on systems with a dedicated pressure pump and a separate dosing or return pump, or on twin-bank SCR architectures.

Unlike a simple circuit code, a performance fault typically indicates a mechanical or hydraulic problem: a worn pump that can no longer build the required DEF pressure, a blocked inlet strainer, frozen or crystallised DEF restricting flow, or a faulty pressure sensor feeding back incorrect data. Air ingestion caused by a low DEF tank or a cracked suction line can also cause intermittent pressure drops that trigger the code.

Diagnosis should begin with DEF quality and level checks before condemning the pump, as contaminated or diluted fluid can crystallise inside the pump assembly.

Common causes

Most-frequently reported root causes when P206B is logged.

  • 1
    Worn or failing reductant pump 'B' unable to reach commanded pressure or flow target
  • 2
    Blocked or partially clogged DEF pump inlet strainer or suction filter
  • 3
    Frozen or crystallised DEF (AdBlue) inside the pump body or supply lines
  • 4
    Air ingestion in the DEF suction line due to low tank level, cracked hose, or loose fitting
  • 5
    Faulty DEF pressure sensor providing incorrect feedback to the ECM
  • 6
    DEF quality out of specification (diluted, contaminated, or wrong concentration of urea)
  • 7
    Internal pump driver circuit degradation causing reduced current output to the pump motor
  • 8
    Wiring harness damage causing high-resistance connection to pump 'B'

Symptoms drivers notice

MIL (check engine light) illuminated
SCR/emissions warning light or DEF warning lamp on
Possible engine torque reduction or power derate (on Euro 6 / EPA2010+ vehicles after extended fault)
Reduced NOx conversion — detectable on emissions test
Intermittent or absent DEF dosing
Possible freeze-up or slow DEF flow in cold ambient conditions

How to diagnose P206B

A typical diagnostic flow when this code is present.

  1. 1
    Confirm the fault with a scan tool: record freeze-frame data
  2. 2
    Inspect DEF tank level and fluid quality: verify urea concentration (32.5 %) with a refractometer
  3. 3
    Perform a visual inspection of the pump 'B' harness connector and wiring
  4. 4
    Check DEF system pressure using the scan tool live data or a DEF pressure gauge
  5. 5
    Remove and inspect the DEF pump inlet strainer for crystallisation or blockage
  6. 6
    If pressure does not build despite clean lines and correct voltage/ground, substitute or bench-test the reductant pump 'B' assembly
  7. 7
    After repairs, clear DTCs, perform a DEF system prime/fill cycle

Vehicles where we've handled P206B

Platforms in our catalogue with confirmed P206B coverage.

VW TRANSPORTER
AUDI A4 20D

Related powertrain codes

Frequently asked questions

Can I keep driving with P206B active?

Short-term driving is generally possible, but the vehicle is not meeting emissions standards and many Euro 6 / EPA2010+ platforms will progressively derate engine torque if the SCR fault persists.

Why did this code appear after cold weather?

DEF (AdBlue) freezes at approximately −11 °C (12 °F). Although SCR systems include a heating circuit to thaw the fluid, a failed heater or accumulated crystallised deposits can prevent the pump from reaching target pressure.

What is the difference between P206A and P206B?

SAE uses the 'A' and 'B' suffixes to distinguish between two separate pump circuits. P206A refers to the primary pump; P206B refers to the secondary circuit.

Will replacing the DEF pump fix this code?

Not necessarily. The code indicates the pump output did not match its command, which can stem from a blocked strainer, bad pressure sensor, wiring fault, or degraded fluid.

Disabling P206B in software

RaceTune can permanently disable P206B — 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 P206B 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 EDC17C74 verified 2 software versions

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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