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Here is a site that will tell you what you need to know. I tried to link you right to the correct page, but it wouldn't work, so if you have trouble navigating here are some instructions to get you in there. This particular one tells you how to pull the codes with a regular meter with a needle.
Go here:
http://www.corral.net/20anngt/
Go to the bottom of the page and click on "The Corral: Late Model Mustang Web Site"
Click on "technical features"
Scroll down and click on "Online Databases"
Click on "EEC-IV Decoder"
Click on "EEC-IV" highlited in the paragraph.
Scroll down and click on "analog-voltmeter"