There is more than likely something else going on instead of, or as well as. The GS's don't have any issues with driving with an abs fault, so limp mode is being triggered by something else engine related. As lexmanic says, check connections (and get the battery checked out as well). I'd also get the codes read for the engine, the EML light doesn't come on for abs sensor faults, ABS and TRC/VSC ones do.