P2063 — Reductant/Regeneration Supply Control Circuit Low

The diagnostic trouble code P2063 indicates a problem related to the control circuit of the vehicle’s reductant (or DEF/AdBlue) system, specifically in the supply or regeneration controls. Essentially, the engine control unit (ECU) detects that the electrical signal responsible for managing the reductant supply is below expected levels. This warning can affect emissions systems and, depending on severity, vehicle performance.

Note that labels and code descriptions may vary between manufacturers. Always consult the specific manufacturer’s technical documentation for precise information.

Manufacturer variations for trouble code P2063

Different vehicle manufacturers may assign different labels or code variations to similar issues within their specific systems. These labels might be seen during diagnostic scans or in vehicle-specific diagnostic tools. It’s essential to be aware of these possible variations to ensure accurate diagnosis.

• BMW: CC-ID 203A
• Ford: Ford DTC P2063 (sometimes under different module contexts)
• Volkswagen/Audi: P2063 (VAG-specific)
• Mercedes-Benz: ECU-specific code P2063
• PSA Group (Peugeot/Citroën): Possibly similar codes related to SCR / AdBlue systems

What does trouble code P2063 mean?

P2063 signals that the vehicle’s ECU has detected a low voltage or insufficient signal in the reductant supply control circuit—specifically related to the SCR (Selective Catalytic Reduction) system. The SCR system uses a reagent called DEF (Diesel Exhaust Fluid) or AdBlue to reduce NOx emissions during exhaust gas treatment.

The ECU constantly monitors various sensors and actuators, including level sensors, injection control modules, and wiring circuits. When a fault is detected—like a weak or missing electrical signal indicating an issue with supply control—the ECU sets this code to alert the driver and store a fault in the system’s memory.

This code often appears in contexts where there may be issues with wiring, sensors, or control modules. It can also be triggered by problems with the DEF pump, the wiring harness, or the control relay.

Severity and risks of trouble code P2063

The severity of P2063 varies depending on the cause. It can be a relatively simple electrical issue or a sign of more significant problems within the SCR system. If ignored, it may lead to increased emissions, failure to pass regulatory inspections, or even damage to emission components over time.

However, in some cases, the vehicle may enter a limp mode or reduce engine performance to protect exhaust systems.

**Can the vehicle be driven?**

**Limited** — it is generally safe to drive temporarily, but repair is highly recommended to avoid further damage and ensure compliance with emissions standards.

Symptoms of trouble code P2063

When this code is active, drivers might notice subtle or more pronounced symptoms such as:

• Check engine light illuminated on the dashboard
• Possible warning message related to emission or SCR system
• Reduced engine power or performance
• Frequent regenerations or exhaust system warnings
• Fuel consumption may increase slightly due to system inefficiencies
• The vehicle may go into limp mode to protect the emissions system

Most likely causes of trouble code P2063

While diagnosing this fault, it is critical to consider several potential causes. Below is a list of the most common, ranked from most to least probable:

1. Wiring or electrical connection issues: Corrosion, damaged wires, or poor connections within the reductant control circuit are the primary suspects.
2. Faulty DEF pump or supply module: If the pump that delivers DEF to the SCR system fails or malfunctions, it can trigger this code.
3. Faulty control relay or circuit protection device: A defective relay can interrupt supply signals, leading to a low circuit signal.
4. Sensor malfunction: For example, a defective level or pressure sensor could cause incorrect signals to the ECU.
5. ECU or module malfunction: Less common, but possible, especially if other related circuits are functioning improperly.
6. Low DEF fluid level or contamination: Although primarily a fluid level issue, if the control system detects low or contaminated DEF, it may trigger faults.

How to diagnose trouble code P2063

For an effective diagnosis, a methodical approach is essential. Always start with basic checks before delving into complex testing.

1. Visual inspection: Examine wiring harnesses, connectors, and grounds related to the SCR and DEF systems. Look for corrosion, damage, or loose connections.
2. Check for other stored codes: Use a scan tool to identify additional related faults, such as sensor or actuator issues.
3. Monitor live data: Observe signals from relevant sensors, such as DEF level sensors, pressure sensors, and control timestamps during operation.
4. Test wiring continuity: Verify electrical continuity along circuits involved in the reductant control circuit.
5. Check relay operation: Test the control relay and associated circuits for proper switching and activation.
6. Inspect DEF pump and supply components: Ensure the DEF pump operates correctly and that there are no blockages or leaks.
7. Perform a system reset: Clear codes and perform a road test to verify if the fault reappears, and if the signals behave as expected.

Possible repairs for trouble code P2063

Addressing P2063 often involves a series of systematic repairs corresponding to probable causes. While some fixes are simple and manageable at the DIY level, others require professional intervention.

• Reconnect or replace damaged wiring and connectors: Basic repair—recommended for minor electrical issues.
• Replace faulty DEF pump or supply module: Requires professional diagnosis; involves removing and installing new components.
• Replace or repair control relay: A straightforward task for a qualified technician.
• Replace defective sensors: Sensors like pressure or level sensors should be replaced by professionals for accurate calibration.
• Update or reprogram ECU: In rare cases, a software update or ECU replacement might be necessary, best performed by authorized technicians.
• Ensure proper DEF fluid level and quality: Top-up or replace contaminated fluid as needed.

Vehicles commonly associated with trouble code P2063 in Europe

This fault can affect a wide array of diesel vehicles, particularly those equipped with SCR-based emission control systems. While specific models can vary, the following manufacturers and engine families are often involved:

Volkswagen Group (VW, Audi, Škoda, SEAT): Vehicles equipped with Euro 6 diesel engines featuring SCR systems.

Peugeot and Citroën (PSA Group): Models with BlueHDi engines utilizing AdBlue technology.

Mercedes-Benz: Diesel models that incorporate SCR systems for emission compliance.

BMW: Diesel variants with SCR and DEF systems.

Note: Exact vehicle model and engine-specific issues should be cross-referenced with manufacturer data for precise diagnosis.

Frequent mistakes with trouble code P2063

When diagnosing or repairing this fault, many technicians or DIY enthusiasts make common mistakes that can prolong resolution or cause further issues:

• Neglecting visual inspection: Skip preliminary checks on wiring and connectors, leading to misdiagnosis.
• Ignoring related codes: Overlooking additional stored faults can hinder accurate diagnosis.
• Replacing parts without testing: Changing components like sensors or pumps without confirming their failure can be costly and ineffective.
• Assuming ECU fault too early: Jumping to ECU replacement without ruling out simpler electrical issues.
• Disregarding fluid quality: Failing to verify DEF fluid levels or contamination before diagnosing hardware faults.

FAQ — trouble code P2063

Q1: Can this code disappear on its own?

A1: Generally not. Once an electrical circuit fault triggers the code, it will stay until the issue is repaired and the system is cleared. Some temporary glitch may clear by itself, but persistent problems will cause the code to return.

Q2: Can I keep driving?

A2: While the vehicle might operate in limited mode temporarily, driving with unresolved issues can risk further damage or increased emissions. It is safest to have the problem diagnosed and repaired promptly.

Q3: Why does the code return after clearing?

A3: This indicates that the underlying fault has not been resolved—such as wiring, a defective sensor, or a failing pump—so the code reappears once the system’s self-test runs again.