Sure, insofar as reflecting infrared light (heat) is pressure...but the Pioneer anomaly is pushing P1 and P2 toward the sun, not away from it.
Stimmt. AndrewC seemed to be poo-poo radiation pressure. The anomaly could simply be the difference between the model of radiation pressure and true radiation pressure. If you model, say, 0.001 kg-meter/sec/sec, plus or minus (say) 0.0001 kg-m/s/s, and the actual radiation pressure is 0.0005, you have an anomaly of 0.0005 kg-m/s/s “towards” the sun, which cannot be “explained” by your model.