Attempt CKP learn procedure as many as 3 times. If PCM receives an incorrect crankshaft to camshaft ratio, PCM will not allow scan tool to enable the learn procedure. Is there any trouble code!

 

 make sure you do what it wants...make sure the parking brake input is being seen. lot of people miss that...also I don't keep on the rev limiter..i just accelerate to what is says and take my foot off. other than that I say follow instructions to a tee and you should be good to go..... i'v seen on some scanners that freeze at that step but the varation gets learned...

 Had the same problem with both my DS708 and Snap On Brick, no confirmation that it relearned crankshaft angle with a 200K mile 99 Chevy Astro with P0300(showed  high misfire counts on cylinders 4 and 5. Relative compression and fuel injector flow tests confirmed no compression or fuel flow deficits. Checked wires, replaced 4 and 5 spark plugs and put on a new cap and rotor, helped a little but still saw misfire counts on 4 and 5 . Ultimately replaced the distributor assembly and resolvedproblem. After a new distributor Did the relearn procedure twice with no confirmation the relearn ever took successfully or not , but just  let it go, because the random misfire issue was resolved.Maybe the timing chain seen better days, but as long as there wasn't a code , I'm not going to keep trying and end up  blowing  a motor.