I have checked the continuity from ecu to ptu and from ptu to coil pack connector. All cylinders check out. I have replaced ptu with new style ptu and wiring harness. I have replaced all of the sprak plugs as well as coil packs and have tested a known working pack on cylinder 4. The connector for cylinder 4 has power and is grounded.
I have tried the CAS test and pulled the coil packs out with spark plugs and grounded them to the plenum. Every cylinder had spark except for cylinder 4. What does this mean? The CAS is bad for just one cylinder? I've called Z1 and they said I've pretty much checked everything they would have. I was showing a Code 21 but it is intermittent. Any ideas?
Follow Ups
No spark on cylinder 4 - apepper719111:16:55 11/13/12