Diesel engines have inherently dirty emissions and need help to address this problem. You can run them extra lean to keep the soot down but that causes high nitrogen oxides (N0x). A common solution is to use a Diesel Exhaust Fluid (DEF) which is injected into the exhaust system to reduce the NOx emissions. Follow this Real Fix to see how a problem with the DEF system on this 2011 RAM truck was diagnosed and corrected.
Vehicle
2011 RAM Cab & Chassis 3500 HD 6.7L
Title
P20EE, Replaced Diesel Exhaust Fluid Dosing Valve
Complaint
The customer states the check engine light is on.
Cause
Connected a scan tool and found code P20EE – SCR NOx Catalyst Efficiency Below Threshold (Bank 1). Performed a visual inspection of the exhaust system and found no obvious faults. Performed a visual inspection of the diesel exhaust fluid and found that there were no leaks, the fluid was clean and at the proper level. Removed the diesel exhaust fluid dosing valve to inspect and found no obtructions in the decomposition tube. Placed the diesel exhaust fluid dosing valve in a container to capture diesel exhaust fluid expelled during flow volume testing. Used scan tool to perform diesel exhaust fluid doser pump override test. Waited test time duration and found the measured fluid collected was below specification. These test results verified the diesel exhaust fluid dosing valve was faulty.
Correction
Replaced the diesel exhaust fluid dosing valve, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.