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I'm working on a 2011 Ram 1500 with a 5.7 Hemi. At all speeds below 70 mph it runs fine but above that it shuts down cylinder 5 but once it gets below 65 it comes back and runs perfectly. I have changed the injector and coil and plugs, but no change. I can see on scan data the injector has no pulse with after 70 mph.
On a hunch, I'd suspect that the loss of injector pulse isn't the problem, it's a symptom. The PCM is probably taking injector pulse away from #5 because it detected a misfire and shut the injector down for catalyst protection purposes.
Being a Hemi, I'd start with cranking and running compression on #5. Compare both to a known good cylinder.
