P202D Leakage of reductant

P202D Leakage of reductant

OBD-II DTC Datasheet

Leakage of reducing agent

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, Ford, Mercedes-Benz, Dodge, Chevrolet, etc. Despite the general nature, the exact repair steps may vary depending on the model year, make, model and transmission configuration.

A stored P202D code means the powertrain control module (PCM) has detected insufficient activity in the reductant / regeneration pump control circuit.

The catalyst system is responsible for reducing (mostly) all exhaust emissions, although some applications are also equipped with a NOx trap.

Exhaust Gas Recirculation (EGR) systems take another step in reducing NOx emissions. However, today's larger, more powerful diesel engines cannot meet strict federal (US) emission standards with just an EGR system, a particulate filter / catalytic converter, and a NOx trap. For this reason, selective catalytic reduction (SCR) systems have been invented.

SCR systems inject a reductant formulation or Diesel Exhaust Fluid (DEF) into the exhaust gases upstream of the particulate filter, NOx trap and / or catalytic converter through a reductant injection valve (solenoid). The precisely calculated DEF injection raises the temperature of the filter element and allows it to work more efficiently. It extends the service life of the filter elements and helps reduce emissions of harmful exhaust gases into the atmosphere. The entire SCR system is controlled and monitored by either the PCM or a stand-alone controller (which interacts with the PCM). In any case, the controller monitors the O2, NOx and exhaust gas temperature sensors (as well as other inputs) to determine the appropriate timing for the DEF (reductant) injection. Precision DEF injection is required to keep the exhaust gas temperature within acceptable parameters and to optimize the filtration of pollutants.

The reductant / regeneration pump is used to pressurize the DEF in the reductant liquid system for use when needed. The PCM monitors the supply pump voltage for continuous fluctuations and load percentage. The PCM also monitors one or more pressure sensors in the reductant supply system to determine if there is a leak in the system.

If the PCM detects a voltage change rate in the reductant/regeneration supply circuit that is outside of acceptable parameters, a code P202F will be stored and the malfunction indicator lamp (MIL) may be illuminated. It may take several ignition cycles for the MIL to illuminate if a failure occurs.

What is the severity of this DTC?

A stored P202D code should be treated as serious and rectified as soon as possible. The SCR system could be disabled because of this. Catalyst damage can occur if the conditions that contributed to the persistence of the code are not corrected in a timely manner.

What are some of the symptoms of the code?

Symptoms of a P202D trouble code may include:

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

What are some of the common causes for the code?

Reasons for this code may include:

• Leakage in reductant tank or lines.
• Reducing agent supply pump internal leak
• Defective pressure sensor in the reductant tank
• Open or short circuit in the reducing agent supply control circuit
• Bad SCR / PCM controller or programming error

What are some steps to troubleshoot the P202D?

Make sure the reductant / regeneration system does not lose pressure (internal or external). Turn on the pump to build up pressure and check the system for external leaks. Use a fuel pressure tester to manually monitor the pressure in the reductant system. Check the feed pump and nozzle for leaks. If leaks (internal or external) are found, they must be repaired before continuing with the diagnosis.

To diagnose the P202D code, you will need a diagnostic scanner, a digital volt / ohmmeter (DVOM), and a source of vehicle-specific diagnostic information.

You can use your vehicle information source to find a Technical Service Bulletin (TSB) that matches your vehicle's year, make and model; as well as engine displacement, stored codes and symptoms detected. If you find it, it can provide useful diagnostic information.

Use a scanner (connected to the vehicle's diagnostic socket) to retrieve all stored codes and associated freeze frame data. It is recommended that you write down this information before clearing the codes and then test drive the vehicle until the PCM enters ready mode or the code is cleared.

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

If the code is reset immediately, the next diagnostic step will require you to search your vehicle information source for diagnostic block diagrams, pinouts, connector faceplates, and component test procedures / specifications.

Step 1

Use the DVOM to test the reductant system pressure sensors according to the manufacturer's specifications. Components that do not pass the test within the maximum allowable parameters should be considered defective.

Step 2

Use your vehicle diagnostic source and DVOM to check the reductant supply pump voltage (usually battery voltage) with the pump activated. If current conditions do not allow activation, use the scanner to manually activate your pump.

Step 3

If the reductant pump is operating, use the DVOM to test the input and output circuits from the fuse panel, PCM, and ignition switch. Disconnect all controllers before using the DVOM for testing.

• Reductant Leak Codes are often attributed to feed pumps that are leaking internally.

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