Technical Description of OBD-II Trouble Code
Performance Issue with Reductant Purge Control Valve
What does that signify?
This is a generic diagnostic trouble code (DTC) that applies to many diesel-powered OBD-II vehicles (1996-newer). This includes vehicles from Chevrolet, GMC, Ford, Mitsubishi, VW, Sprinter, Audi, and others. While the steps for repair may vary depending on the year, make, model, and powertrain configuration, the code is considered generic.
OBD-II trouble code P20A1, along with related codes P20A0, P20A2, P20A3, P20A4, and P20A5, is associated with the circuit of the reductant purge control valve. This circuit is 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 Engine Control Module (ECM) as a reference point for determining 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 into Nitrogen, Carbon Dioxide, and water in order to protect the environment.
When the PCM or ECM detects a performance issue with the reductant purge control valve, it sets code P20A1 and illuminates the check engine light.
A mechanic:
What is the severity of this DTC?
Typically, the severity of this code is moderate. However, if harmful gases are being expelled from the exhaust, it can become a safety concern that requires immediate attention.
What are some of the symptoms of the code?
Symptoms of a P20A1 trouble code may include:
What are some of the common causes of the code?
Possible causes for this P20A1 code may include:
What are some P20A1 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 based on its year, model, and power plant. This can save a lot of time in the long run by providing guidance in the right direction.
The second step is to locate all components associated with the reductant purge control valve circuit and inspect them for any obvious physical damage. Depending on the specific vehicle, the DEF system may include several components such as 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. Conduct a thorough visual inspection to check the associated wiring for any visible defects like scraping, rubbing, bare wires, or burn spots. Next, check the connectors and connections for security, corrosion, and damaged pins. This process should include all wiring connectors and connections to all components, including the PCM or ECM. Consult the specific technical data for the vehicle to determine if a fuse or fuse-able link is part of the circuit.
Advanced Steps
The advanced steps are highly vehicle-specific and require the appropriate advanced equipment for accurate performance. These procedures necessitate the use of a digital multimeter and specific technical references for the vehicle. In some cases, a pressure gauge may also be necessary to aid in the troubleshooting process.
Voltage Checks
The reference voltage and acceptable ranges may vary depending on the specific vehicle and circuit configuration. The specific technical data will include troubleshooting charts and the appropriate sequence to follow for an accurate diagnosis.
If this process reveals the absence of a power source or ground, continuity testing may be necessary to check the integrity of the wiring, connectors, and other components. Continuity tests should always be conducted with the power removed from the circuit, and the normal readings for wiring and connections should be 0 ohms of resistance. Resistance or lack of continuity indicates faulty wiring that is either 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 indicates 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 guiding you towards resolving the issue with your reductant purge control valve circuit fault code. This article is purely informational, and the specific technical data and service bulletins for your vehicle should always take precedence.
