P20D7 Exhaust Gas Treatment System Fuel Control Circuit / Open

P20D7 Exhaust Gas Treatment System Fuel Control Circuit / Open

OBD-II DTC Datasheet

Exhaust gas aftertreatment system fuel control circuit / open

What does this mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code and applies to many OBD-II vehicles (1996 and newer). This may include but is not limited to VW, Audi, Mercedes Benz, Ford, Mitsubishi, etc. Despite the general nature, the exact repair steps may vary depending on the model year, make, model and transmission configuration.

A stored code P20D7 in your diesel vehicle means that the powertrain control module (PCM) has not detected voltage on the aftertreatment fuel control circuit.

An Exhaust Aftertreatment System (also called a Selective Catalyst Recovery System) is used to enhance the capabilities of the catalytic exhaust gas system. It can consist of one or more of these elements; diesel oxidation catalyst, particulate filter, reducing agent injection system, ammonia slip catalyst and nitrogen oxide (NOx) trap.

A reductant injection system typically consists of at least one reductant injector, a reductant storage tank, and high pressure reductant fuel lines. An electronic high pressure pump is usually located in the tank or in the fuel supply line. It was in the circuit that controls this feed pump that the storage fault of the P20D7 was detected.

Among other things, exhaust gas aftertreatment systems (EAS) are responsible for injecting a reductant / diesel engine fluid (DEF) compound into the exhaust gases upstream of the particulate filter, NOx trap and / or catalytic converter via an automated fluid storage. and injection system. The precisely calculated DEF injections raise the temperature of the various filter elements and enable them to operate more efficiently. The addition of DEF to the catalytic system extends the life of the filter element and reduces emissions of harmful exhaust gases into the atmosphere.

EAS systems and catalysts are monitored and controlled by either the PCM or a stand-alone controller (which interacts with the PCM). The controller monitors the pressure in the reductant injection system, the O2, NOx and exhaust gas temperature sensors (as well as other inputs) to determine the appropriate timing for the DEF (reductant) injection.

If the PCM detects a lack of voltage in the EAS fuel pump control circuit, a code P20D7 will be stored and the malfunction indicator lamp may illuminate.

What is the severity of this DTC?

A stored P20D7 code should be treated as serious and rectified as soon as possible. The EAS system can be damaged as a result of conditions that contributed to the persistence of the P20D7 code.

What are some of the symptoms of the code?

Symptoms of a P20D7 trouble code may include:

• Reduced engine performance
• Excessive black smoke from vehicle exhaust
• Decreased fuel efficiency
• Other codes related to EAS / SCR

What are some of the common causes for the code?

Reasons for this code may include:

• Defective EAS fuel pump
• Defective fuel pressure sensor EAS
• Open or short circuit in the EAS fuel supply control circuit
• Insufficient DEF in the EAS reservoir
• Bad EAS / PCM controller or programming error

What are some steps to troubleshoot the P20D7?

Diagnosing a P20D7 code will require a diagnostic scanner, digital volt / ohmmeter (DVOM), and vehicle-specific diagnostic source.

Search for a Technical Service Bulletin (TSB) that matches the year of manufacture, make and model of the vehicle; as well as engine displacement, stored codes, and detected symptoms can provide useful diagnostic information.

I like to start my diagnosis with a visual inspection of the EAS wiring harnesses and connectors. Burnt or damaged wiring and / or connectors must be repaired or replaced before proceeding.

I would proceed by connecting the scanner to the vehicle's diagnostic connector and retrieving all stored codes and associated freeze frame data. Make a note of this information before clearing codes. Test drive the vehicle until the PCM enters readiness mode or the code is cleared.

If the PCM enters ready mode during this time, the code is intermittent and can be much more difficult to diagnose. If so, the conditions that contributed to the retention of the code may need to worsen before an accurate diagnosis can be made.

If the code resets immediately, the next diagnostic step will require searching the vehicle information source for diagnostic block diagrams, pinouts, connector faces, and component test procedures and specifications.

Use the DVOM to check (voltage drop) on all EAS fuel system grounds. Continue testing the EAS control system power supply. Check the fuses with a loaded circuit to avoid misdiagnosis. If the correct power (battery voltage) and ground circuits are found, use the scanner to turn on the EAS fuel pump and check the control circuit output voltage. If the voltage is insufficient, check the EAS fuel pump relay. If no input voltage is detected, suspect that the controller is defective or has a programming error. If an input voltage is present at the relay but no output voltage is detected, suspect that the relay is faulty.

If the EAS power supply voltage output circuit is within parameters, use the DVOM to test the EAS fuel pressure sensor and fuel pump. If any of these components do not meet manufacturer's specifications, suspect that it is defective.

• Do Not Forget Ground Loops When Testing Voltage Drop

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