By using the concept of parameter varying (CA)invariant subspace and parameter varying unobservability subspace, this paper investigates the problem of fault detection and isolation for quasi linear parameter varying (qLPV) systems. The so called detection filters approach, formulated as the fundamental problem of residual generation (FPRG) for linear time invariant (LTI) systems is extended for a class of qLPV systems. The parameter dependence in the state matrix of these qLPV systems is assumed to be in affine form. The question of stability is addressed in the terms of Lyapunov quadratic stability by using an LMI technique. A numerical example is also provided.