Reductant Purge Control Valve Circuit Low
The P20A2 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the reductant purge control valve circuit. This valve is part of the selective catalytic reduction (SCR) system, which injects diesel exhaust fluid (DEF) into the exhaust stream to reduce NOx emissions. A low circuit voltage typically points to a short to ground, open circuit, or a faulty valve, preventing proper DEF purge and potentially leading to increased emissions.
1. Most Common Causes
- Internal short circuit in the DEF purge valve
- Control circuit wiring shorted to ground (chassis)
- Damaged, corroded, or bent pins in the valve connector
- Internal failure of the valve driver within the PCM/ECM
- Ground supply issues in the SCR control module
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Visually inspect the reductant purge control valve and its wiring for damage, corrosion, or loose connections.
Step 3: Test the valve's resistance with a multimeter; compare to manufacturer specs (typically 10-30 ohms).
Step 4: Check for voltage at the valve connector with the ignition on; should see battery voltage. If not, trace circuit for opens/shorts.
Step 5: If all tests pass, suspect a faulty PCM; perform a PCM reset or reprogram if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to reduced engine performance, increased emissions, and potential damage to the SCR system. You may experience limp mode.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the valve needs replacement or just wiring repair. Parts cost around $30-$80, labor $50-$100.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.