Complete reducibility in bad characteristic

Let G be a simple algebraic group of exceptional type over an algebraically closed field of characteristic p > 0. This paper continues a long-standing effort to classify the connected reductive subgroups of G. Having previously completed the classification when p is sufficiently large, we focus here on the case that p is bad for G. We classify the connected reductive subgroups of G which are not G-completely reducible, whose simple components have rank at least 3. For each such subgroup X, we determine the action of X on the adjoint module L(G) and on a minimal non-trivial G-module, and the connected centraliser of X in G. As corollaries we obtain information on: subgroups which are maximal among connected reductive subgroups; products of commuting G-completely reducible subgroups; subgroups with trivial connected centraliser; and subgroups which act indecomposably on an adjoint or minimal module for G.