P20DD: Exhaust Aftertreatment Fuel Pressure Sensor Circuit

Is your scanner showing P20DD?
No worries. We'll show you what it means and how to deal with it.

Presented by

Randy Worner

00:00/00:00

P20DD: Exhaust Aftertreatment Fuel Pressure Sensor Circuit

OVERVIEW

Severity

High

DIY Difficulty Level

Intermediate

Repair Cost

$250-$400

Can I Still Drive?

Yes

What Does The P20DD Code Mean?

A stored a code P20DD in your diesel powered vehicle means that the powertrain control module (PCM) has detected improper voltage in the fuel pressure sensor circuit for the exhaust aftertreatment system.

The exhaust aftertreatment system (also called selective catalyst reduction system) is used to enhance the capabilities of the exhaust catalyst system. It may consist of one or more of these items; diesel oxidation catalyst, diesel particulate filter, reductant injection system, ammonia slip catalyst, and a nitrogen oxide (NOx) trap.

The reductant injection system is typically composed of at least one reductant injector, a reductant fuel storage tank, and high-pressure reductant fuel lines. A high-pressure, electronic pump is normally situated in the tank or in the fuel supply line. An EAS fuel pressure sensor allows the controller to monitor system pressure when the supply pump is activated. It is within this circuit that a malfunction has been perceived when a code P20DD is stored.

Among other things, exhaust aftertreatment systems (EAS) are responsible for the injection of reductant compound/diesel exhaust fluid (DEF) into the exhaust in front of the diesel particulate filter, NOx trap, and/or the catalytic converter via an automated fluid storage and injection system. Precisely timed DEF injections elevate the temperature of the various filtration elements and allow them to perform more efficiently. Introducing DEF into the catalyst system promotes filtration element longevity and allows fewer harmful exhaust emissions to be released into the atmosphere.

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

If the PCM detects improper voltage in the circuit for the EAS fuel pressure sensor, a code P20DD will be stored and a malfunction indicator lamp may be illuminated.

What Are The Symptoms Of The P20DD Code?

Symptoms of a P20DD trouble code may include:

Diminished engine performance
Excessive black smoke from vehicle exhaust
Reduction in fuel efficiency
Other EAS/SCR related codes

What Are The Potential Causes Of The P20DD Code?

Causes for this code may include:

Defective EAS fuel pressure sensor
Bad EAS fuel supply pump
Open or shorted wiring in the EAS fuel pressure sensor circuit
Bad EAS controller/PCM or programming error

How Serious Is This P20DD Code?

A stored code P20DD should be considered severe and addressed as quickly as possible. The EAS system may be damaged as a result of the conditions which contributed to the code P20DD being stored.

How Can You Fix The P20DD Code?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle specific diagnostic information will be required to diagnose a code P20DD.

Locate a technical service bulletin (TSB)

Locating a technical service bulletin (TSB) that matches the vehicle year, make, and model; as well as the engine size, code/s stored, and symptoms exhibited, could yield helpful diagnostic information.

Visually inspect the EAS wiring harnesses and connectors

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

Retrieve all stored codes

I would continue by plugging the scanner into the vehicle diagnostic connector and retrieving all stored codes and pertinent freeze frame data. Consider writing this information down before clearing the codes. Test drive the vehicle until the PCM either enters readiness mode or the code is reset.

If the PCM enters readiness mode at this time, the code is intermittent and may be much more difficult to diagnose If this is the case, the conditions which contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, completing the next step of your diagnosis will require that you search your vehicle information source to obtain diagnostic flow charts, connector pin-out charts, connector face views, as well as component testing procedures and specifications.

Use the DVOM to test the power supply

Use the DVOM to test (voltage drop) on all EAS fuel supply system grounds. Continue by testing the power supply to the EAS control system. Test fuses with the circuit loaded to avoid misdiagnosis.

If all system fuses are intact, use the DVOM to test the EAS fuel pressure sensor and sensor circuits. If any of these components fails to meet manufacturer’s specifications, suspect that it has failed.