01 This Engine Feature Saves Gas But Could Bankrupt Your Wallet • 02 Why The Traction Control Light Comes On During Normal Drivi… • 03 U0020 Low Speed CAN Communication Bus Performance • 04 This Is How to Fix a Car That Won’t Start After Replacing t… • 05 Why You Should Follow The Wheel Tightening Sequence • 06 Why Dirty Grounds Cause More Car Problems Than People Reali… • 07 Transmission Troubleshooting: What Does It Mean When Your C… • 08 How Low Can Tire Pressure Be Before It Becomes Unsafe to Dr… • 09 Manual Transmission Driving Techniques for Improved Fuel Ef… • 10 Master Your Automatic: A Guide to Using D, D1, D2, D3 Gear … •

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20A3

P20A3Reductant Purge Control Valve A Circuit High

P20A3 indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the control circuit for the reductant purge control valve, which is part of the diesel exhaust fluid (DEF) system. The PCM expects the circuit to pull to a certain voltage when the valve is commanded, but the signal remains above the expected threshold, indicating an open circuit, a short to voltage, or a faulty valve.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp, MIL), often with no other symptoms.
  • A driver information message indicating a problem with the emissions system or diesel exhaust fluid (DEF) system.
  • Possible reduction in engine power or activation of limp mode if the fault triggers a derate strategy.
  • Increased diesel exhaust fluid consumption or failure to purge the reductant line, which may lead to DEF crystallization over time.
  • In some cases, the vehicle may fail an emissions inspection due to the stored fault.

Common causes, most likely first

  1. Open circuit in the reductant purge control valve control wire, such as a broken wire or poor connection.
  2. Short to voltage on the control circuit, often caused by chafed wiring contacting a power source.
  3. Failed reductant purge control valve solenoid, where the internal coil is open or shorted.
  4. Corroded or damaged electrical connector at the valve or PCM, leading to high resistance or intermittent contact.
  5. Faulty powertrain control module (PCM) driver circuit, though this is less common.
  6. Aftermarket accessories or improper wiring repairs that interfere with the circuit.

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes and freeze-frame data to confirm P20A3 is the primary fault and not a secondary code.
  2. Visually inspect the reductant purge control valve, its connector, and the wiring harness for damage, corrosion, or loose pins.
  3. Disconnect the valve connector and measure resistance across the valve solenoid terminals; compare to the manufacturer's specification to check for an open or shorted coil.
  4. With the connector disconnected and the key on, measure voltage on the control circuit from the PCM side to ground; it should be near zero volts when the valve is not commanded, indicating no short to voltage.
  5. Check for continuity between the PCM connector and the valve connector on the control wire to rule out an open circuit.
  6. If the circuit tests good, command the valve on with a scan tool and observe if the voltage signal changes as expected; if not, suspect a faulty PCM or valve.
  7. Replace the reductant purge control valve if it fails electrical tests, clear codes, and verify the repair with a test drive that includes a purge cycle.

Reductant Purge Valve Circuit Traps

  • A high voltage code often results from an open circuit rather than a short, so technicians who only look for shorts to power may miss a broken wire or poor ground.
  • The reductant purge control valve may be part of a larger DEF injector or dosing module on some vehicles, making replacement more involved than a simple solenoid swap.
  • Intermittent faults can be caused by water intrusion into the connector, which may not be obvious until the harness is flexed or the connector is opened.
  • A faulty purge valve can cause DEF to crystallize in the line, leading to additional codes and symptoms even after the electrical fault is repaired.
  • Some vehicles require a relearn or adaptation reset after replacing the valve, which a generic scan tool may not support.

Can I keep driving with P20A3?

You can usually drive the vehicle with this code, but avoid long trips or heavy loads until it is repaired because the fault may trigger a power derate and increased DEF consumption. If the check engine light starts flashing or a limp mode message appears, stop driving and seek service immediately.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage