Contaminants-in-Diesel Exhaust Fluid Diagnosis

Contaminants-in-Diesel Exhaust Fluid Diagnosis

Description

Maximum oxides of nitrogen (NOx) reduction efficiency of the Selective Catalyst Reduction (SCR) system requires the supply of diesel exhaust fluid (DEF) or reductant. Consisting of a mixture of 32.5% urea and 67.5% deionized water, fresh DEF should be clear in color with an ammonia smell. DEF designed for SCR systems should carry one or more of the following international certifications:

* DIN70700
* ISO 22241-1
* American Petroleum Institute (API) Certification

Inspecting for Contaminates

While contamination may result from any number of fluids, it's more likely that contamination will involve one the following common automotive fluids. As clean DEF is clear, contamination by any of these fluids will cause the DEF to exhibit a trace of color associated with a specific contaminate.

* Windshield washer solvent - orange or blue
* Engine coolant - orange or green
* Engine oil - brown
* Transmission fluid - red or brown
* Diesel fuel - clear, yellow, green or brown

Reference Information
Description and Operation

Exhaust Aftertreatment System Description Emission Control Systems
Scan Tool Reference

Control Module References Control Module References for scan tool information
Special Tools

J 26568 Coolant and Battery Fluid Tester

Circuit/System Testing

1. Collect a DEF sample of about 150 ml (5 oz) from the DEF tank in a clear container.
Observe the DEF sample. The DEF sample should be clear with no obvious coloration when held up to a light.

Note: If the engine was never started and the sample is contaminated with diesel fuel, engine oil, transmission oil, or other petroleum-based product, only replace the emission reduction fluid tank and flush the emission reduction fluid tank opening filler.

• If the engine has been started and the sample is contaminated with diesel fuel, engine oil, transmission oil, or other petroleum-based product, flush the emission reduction fluid tank opening filler and replace the following components:

* Emission reduction fluid tank
* Emission reduction fluid injector
* Emission reduction fluid exhaust front pipe injector supply pipe

• If the sample is contaminated with engine coolant or windshield washer solvent, flush the Diesel Exhaust Fluid System.

2. Observe the DEF sample. The DEF sample should have an ammonia smell.
3. Measure the refractive index of the DEF sample using the J 26568 . The refractive index of pure DEF should be between 1.310-1.3843 at 20°C (68°F).

• If not within the specified range, drain the remaining DEF and refill the tank with fresh DEF.

4. If the DEF tests normal, perform the DEF Quality test with a scan tool. The DEF Quality test should pass.

• If the test fails, replace the DEF.

Repair Instructions

* Emission Reduction Fluid Exhaust Front Pipe Injector Supply Pipe Replacement Service and Repair
* Emission Reduction Fluid Injector Replacement Service and Repair
* Emission Reduction Fluid Tank Replacement Emission Reduction Fluid Tank Replacement
* Perform the Diesel Particulate Filter (DPF) Regeneration Enable Diesel Particulate Filter (DPF) Regeneration Enable

Repair Verification

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Ignition OFF, all vehicle systems OFF, this may take up to 2 minutes.

Note: The diesel exhaust fluid (DEF) and ambient air temperatures must be greater than -7°C (19°F) before proceeding with this procedure.

5. Ignition ON, command the Reductant System Leak Test ON with a scan tool. Allow the pressure to build for at least 2 minutes. Observe the scan tool Reductant Pressure sensor parameter. The reading should be between 425-575 kPa and there should be no leaks in the system.
6. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.