I ran the KOER test (ACTRON CP9145) on my 1994 F150 5.0L and received a code 538 "insufficiant rpm during selftest".
Does that mean I need to increase the RPM's during the test or is it pointing out a problem. And if it is a problem what is it pointing to?

 

When you're running the test, you're supposed to rev the engine when it prompts you. If you didn't, that will cause the error you're getting.

 

Thanks, I will try it again.