What it means
This code indicates a low voltage condition in the reductant purge control valve circuit. It does not identify an evaporative fuel-vapor system fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reductant purge valve A opens at shutdown to vent DEF lines back toward the tank, helping prevent freeze damage. The control module monitors the valve's electrical drive circuit and sets P20A2 when its voltage is lower than expected; this does not by itself prove a short to ground.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Check freeze-frame data and reductant-system status to establish when the low circuit reading occurred and whether valve A was commanded.
- Inspect valve A's connector and harness for corrosion, poor terminal contact, or chafed insulation that could pull the circuit low.
- Use the wiring information to check the valve drive circuit for an unwanted path to ground and inspect the control-module connector.
- Measure circuit voltage at valve A and at the module during the specified command, comparing readings with the manufacturer's specification.
- If wiring checks out, test the valve coil and module driver using the manufacturer's procedure.
Common fixes
- Repair chafed wiring or a confirmed short to ground in valve A's drive circuit.
- Clean corroded connector pins and restore secure terminal contact.
- Replace a damaged connector or terminal causing excessive resistance.
- Replace purge valve A if its coil fails the manufacturer's test.
- Repair the control module driver if testing confirms it is faulty.
Can I keep driving?
The vehicle may keep running, but valve A may not purge the DEF lines at shutdown, which raises the risk of freeze damage in cold weather. Arrange repair promptly if freezing temperatures are expected.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.