P208C

Reductant Pressure Too Low

P208C is a generic OBD-II powertrain diagnostic trouble code: Reductant Pressure Too 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
P208C
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P208C means

P208C is stored when the SCR control module determines that the reductant (DEF/AdBlue) system pressure has fallen below the minimum threshold required for proper dosing into the exhaust stream. The reductant pump is responsible for pressurizing the supply line from the DEF tank to the dosing injector, and adequate pressure is essential for accurate metering.

Insufficient pressure prevents the dosing injector from delivering the correct quantity of reductant to the SCR catalyst. Without adequate reductant dosing, NOx conversion efficiency drops, and additional SCR efficiency or NOx sensor faults may be set. In many vehicles, persistent low reductant pressure will eventually trigger a torque or speed derate to ensure emissions compliance.

Diagnosis should start with verifying that the DEF tank contains sufficient fluid, followed by an inspection of supply lines and fittings for leaks or kinks. The reductant pump, pressure sensor, and dosing injector should all be evaluated in a systematic order to isolate the root cause before any parts are replaced.

Common causes

Most-frequently reported root causes when P208C is logged.

  • 1
    Low DEF fluid level in the reductant tank.
  • 2
    Reductant supply pump failing or seized and unable to build pressure.
  • 3
    Blocked or kinked reductant supply line restricting flow.
  • 4
    Leaking supply line fitting or connection losing pressure.
  • 5
    Clogged reductant filter restricting pump inlet flow.
  • 6
    Faulty reductant pressure sensor providing inaccurate readings.
  • 7
    Frozen reductant in supply lines in cold ambient conditions.

Symptoms drivers notice

MIL and possibly a dedicated AdBlue or SCR warning lamp illuminated.
Scan tool live data shows reductant line pressure below target value.
Possible NOx efficiency fault codes stored alongside P208C.
In severe or prolonged cases, vehicle may enter a derate mode limiting speed or power.
No immediate driveability symptom other than warning lights in early stages.

How to diagnose P208C

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze-frame data with a scan tool; note any accompanying NOx or SCR efficiency codes.
  2. 2
    Verify that the DEF tank has adequate fluid level and that the fluid is not frozen.
  3. 3
    Inspect all reductant supply lines and fittings for visible leaks, kinks, or damage.
  4. 4
    Check the reductant filter condition and replace if it is at service interval or visibly clogged.
  5. 5
    Command the reductant pump on with a scan tool and observe live pressure data to determine if the pump can build pressure.
  6. 6
    If pressure does not build, measure pump supply voltage and ground integrity before condemning the pump.
  7. 7
    If pressure builds but the code persists, compare sensor output voltage to actual pressure and consider sensor replacement.

Vehicles where we've handled P208C

Platforms in our catalogue with confirmed P208C 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 a low DEF level alone trigger P208C?

Yes. If the DEF level is too low, the pump may cavitate or draw air, causing pressure to fall below the minimum threshold and setting this code.

Will P208C clear itself after refilling DEF?

If the only cause was low fluid level, refilling the tank and performing a system prime cycle may allow the code to clear, but a manual clear with a scan tool is often required.

Is P208C dangerous to ignore?

Ignoring it risks reduced NOx conversion efficiency and eventually a torque or speed derate, which can leave the driver in a difficult situation, particularly on a highway.

How is P208C different from P208D?

P208C indicates reductant pressure is too low, while P208D indicates pressure is too high. They point to opposite failure modes and require different diagnostic approaches.

Disabling P208C in software

RaceTune can permanently disable P208C — 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 P208C 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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