Technical Description of OBD-II Trouble Code
The reductant purge control valve is stuck closed.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that applies to many OBD-II diesel powered vehicles (1996-newer), including vehicles from Chevrolet, GMC, Ford, Mitsubishi, VW, Sprinter, Audi, etc. The exact repair steps may vary depending on the year, make, model, and powertrain configuration.
OBD-II trouble code P20A5 and related codes P20A0, P20A1, P20A2, P20A3, and P20A4 are associated with the reductant purge control valve circuit, also known as the diesel exhaust fluid system (DEF).
The purpose of the reductant purge control valve circuit is to send a signal to the Power Control Module (PCM) or the Engine Control Module (ECM) as a reference point to determine when the reductant pump needs to reverse flow and purge the DEF system. This process helps convert leftover exhaust particles into harmless gases. The DEF system is designed to convert harmful NOx gases to Nitrogen, Carbon Dioxide, and water to protect the environment.
When the PCM or ECM detects a stuck closed reductant purge control valve, it sets code P20A5 and illuminates the check engine light.
A mechanic:
What is the severity of this DTC?
The severity of this code is normally moderate, but it can be severe if harmful gases are being expelled from the exhaust, posing a safety concern that requires immediate attention.
What are some of the symptoms of the code?
Symptoms of a P20A5 trouble code may include:
What are some of the common causes of the code?
Causes for this P20A5 code may include:
What are some P20A5 troubleshooting steps?
The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins (TSB’s) for the specific vehicle by year, model, and power plant. In some circumstances, this can save a lot of time in the long run by pointing you in the right direction.
The second step is to locate all components associated with the reductant purge control valve circuit and look for obvious physical damage. Based on the specific vehicle, the DEF system may incorporate several components, including an electrically operated reductant pump, purge valve, pressure sensor, integrated level sensor, temperature sensor, system heaters, filters, an electrically controlled reductant injector, and a reservoir. Perform a thorough visual inspection to check the associated wiring for obvious defects such as scraping, rubbing, bare wires, or burn spots. Next, check the connectors and connections for security, corrosion, and damaged pins. This process must include all wiring connectors and connections to all components, including the PCM or ECM. Consult the specific tech data for the vehicle to see if a fuse or fuse-able link is incorporated into the circuit.
Advanced Steps
The advanced steps become very vehicle specific and require the appropriate advanced equipment to perform accurately. These procedures require a digital multi meter and the specific technical references for the vehicle. In this situation, a pressure gauge may also be required to assist the troubleshooting process.
Voltage Checks
The reference voltage and the acceptable ranges may vary based on the specific vehicle and the circuit configuration. Specific technical data will include troubleshooting charts and the appropriate sequence to follow, assisting you with an accurate diagnosis.
If this process identifies the absence of a power source or ground, continuity testing may be required to check the integrity of the wiring, connectors, and other components. Continuity tests should always be performed with the power removed from the circuit, and the normal readings for wiring and connections should be 0 ohms of resistance. Resistance or no continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced. A continuity test from the PCM or ECM to the frame will confirm the serviceability level of ground straps and ground wires. The presence of resistance is an indication of a loose connection or possible corrosion.
What are some common repairs for this code?
Common Mistake
Hopefully, the information in this article has been helpful in pointing you in the right direction to correct the problem with your reductant purge control valve circuit fault code. This article is strictly informational, and the specific technical data and service bulletins for your vehicle should always take priority.
