P208A

Reductant Pump Control Circuit Low

P208A is a generic OBD-II powertrain diagnostic trouble code: Reductant Pump Control Circuit Low. 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
P208A
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P208A means

P208A is set when the SCR or engine control module detects a lower-than-expected voltage on the reductant pump control circuit. The reductant pump is driven through a dedicated control circuit, and the module monitors circuit voltage to confirm the pump is being commanded and responding correctly.

A low voltage condition on this circuit typically indicates a short to ground in the pump control wiring, excessive resistance in the ground path, a failed pump drawing too much current, or a driver circuit fault within the control module. The fault disables or impairs reductant dosing, which reduces SCR catalyst efficiency and can lead to NOx exceedance and derate conditions if left unresolved.

Technicians should begin diagnosis with a thorough wiring inspection for shorts and damaged insulation, followed by verification of proper supply voltage and ground at the pump connector. Component-level testing of the pump motor resistance and the module output driver should follow before any parts are ordered.

Common causes

Most-frequently reported root causes when P208A is logged.

  • 1
    Short to ground in the reductant pump control wiring.
  • 2
    Damaged or corroded pump connector causing unintended ground path.
  • 3
    Pump motor winding failure resulting in abnormally low resistance.
  • 4
    Failed control module output driver providing a continuously low signal.
  • 5
    Chafed harness contacting vehicle ground near the DEF tank area.
  • 6
    Incorrect pump installed with a different electrical specification.
  • 7
    Water or DEF fluid ingress into the pump connector causing a short.

Symptoms drivers notice

MIL illuminated with P208A stored.
Reductant pump may not operate or may operate erratically.
No reductant pressure build-up observed on scan tool live data.
SCR system unable to dose DEF, potentially causing NOx efficiency faults.
AdBlue or SCR warning lamp may illuminate on the instrument cluster.

How to diagnose P208A

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all stored DTCs and freeze-frame data before any component testing.
  2. 2
    Inspect the reductant pump wiring harness and connector for shorts, chafing, or fluid intrusion.
  3. 3
    Measure voltage at the pump control circuit with the pump commanded on and verify it is within specification.
  4. 4
    Measure the resistance of the pump motor windings and compare to the expected range.
  5. 5
    Verify that the pump supply voltage and ground connections are clean and within specification.
  6. 6
    If wiring and pump test acceptable, perform an actuator test via scan tool and monitor module output voltage live.
  7. 7
    If the module output remains low during the actuator test with no wiring fault found, suspect an internal module driver failure.

Vehicles where we've handled P208A

Platforms in our catalogue with confirmed P208A coverage.

AUDI A4 20D
VW TRANSPORTER
AUDI A6
2015
AUDI A7
AUDI A7 30D
AUDI A6 30D
2015

Related powertrain codes

Frequently asked questions

Can P208A be caused by a bad ground rather than a short?

Yes. A poor pump ground connection can cause voltage imbalances that the module interprets as a low circuit condition, setting P208A.

Is P208A the same as the pump being completely dead?

Not necessarily. The pump may still turn but the electrical circuit monitoring detects a low voltage anomaly. The pump could be partially functional or the wiring may be at fault.

Will the vehicle derate immediately when P208A sets?

Typically not immediately. Derate usually follows after the system confirms that dosing has been absent for an extended period and NOx thresholds are exceeded.

Do I need a scan tool to diagnose P208A?

A scan tool is strongly recommended to observe live pump circuit data, perform actuator commands, and distinguish between wiring faults and module driver failures.

Disabling P208A in software

RaceTune can permanently disable P208A — 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 P208A 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
  • Bosch EDC17CP44 verified 1 software version
  • Bosch MD1CP004 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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