The man sat with his son's head on his lap in his fume-filled car in the garage of their home, planning to die with him - but was saved when his wife discovered them, Coventry Crown Court was told.
Rajnikant Penkhania, 42, of Coundon, Coventry, was put on probation for three years. He denied murdering his 11-year-old son Manoj but admitted manslaughter.
Manoj, who had the mental age of a six-week-old, was a spastic, a quadraplegic, suffered from epilepsy, multiple sclerosis and a breathing disorder and had also gone blind, Roger Smith QC, for the prosecution, said.
Jonathan Caplan QC, for the defence, said Penkhania, an education officer, suffered from memory loss as a result of the fumes. He had been a devoted father but could not bear to see the boy suffer any more, with no prospect of improvement.
Penkhania was put on probation with a condition that he received treatment for depression.