HI there, IA m Cam. This could be a fluid quality issue or even an injector issue. The 2 codes have this PI which is simply information.
#PIP4991: Duramax Diesel Exhaust Fluid Quality Poor Message DTCs P207F P20EE P2BAD - (Jan 13, 2012)
Duramax Diesel Exhaust Fluid Quality Poor Message DTCs P207F P20EE P2BAD
2010 - 2012 Chevrolet Express
2010 - 2012 GMC Savana
2011 - 2012 Chevrolet Silverado
2011 - 2012 GMC Sierra
Equipped with the 6.6L Duramax Diesel engine RPO codes LGH and LML
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
A dealer may encounter a customer concern of the “Exhaust Fluid Quality Poor” indicator coming on. Diagnostics may show DTCs P207F, P20EE, or P2BAD have set. “Vehicle Speed Limited” message may be shown on DIC.
Complete the current SI diagnostic for any trouble code or symptom found.
During diagnosis of a P207F P20EE it is important to check for any diesel fuel quality concerns. The diesel fuel contamination may not be bad enough to cause a noticeable engine drivability condition, but may increase NOx levels, and induce P207F, P20EE, or P2BAD to set.
Take a large fuel sample from the fuel filter drain. Fuel samples inspected for this condition has not shown to have heavy contaminates or water. The fuel may just look different in color when compared to a like sample.
Question the customer about where they are buying their fuel, and if they have their own fuel source. Check the API of the fuel and compare to known good sample. Use the SI document for "Fuel Specific Gravity Testing". If the sample taken from the vehicle has the same API and color as the known good fuel sample, continue with the current diagnostics for P207F and P20EE, and repair the vehicle as necessary.
If a fuel quality concern is suspected, the vehicle should be evaluated with fresh clean fuel before attempting repairs.
Note: It is possible for the customer to have access to off road diesel fuel with sulfur content higher than 15 PPM. If off road diesel fuel is being used, evaluate the condition with known good Ultra Low Sulfur Diesel Fuel.
Note: After the fuel has been changed use the tech 2 to complete a Diesel Particulate Filter Service Regeneration, and a Reductant Fluid Quality Test. These functions will purge the SCR/DPF assembly of contaminants.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
u029D is a loss of communications with NOX sensor 1 which is the NOX sensor in the turbo.