To make clear the relevance of access to the PJ line, it bypasses the need to go through the (sometimes) chaotic Sentral nexus, and instead travel by metro to Putra Jaya, where it's possible to catch the KLIA Transit train to the airport.

Putra Jaya to KLIA is MYR 9, against the Sentral KLIA fare of MYR 55. The Ampang Park to PJ sector by metro is round MYR 4 (depending on cash or cashless purchase).

It's a long ride with frequent stops on the metro, and not exactly seamless: and there's the prospect of a longish wait at PJ (Transit trains run at 30 minute intervals). But if you're heading for the IC or DoubleTree, or anywhere else on the PJ line, it's likely the easiest (and certainly the cheapest!) way to get there.