The types and specifications of Ford engines do not play a role in conducting engine diagnostics. The process is always going to be the same, with one major exception. If the Ranger was manufactured after 1996, then it complies with the second generation of On-Board Diagnostics. To effectively troubleshoot the check engine light, you will need an OBD-II scanner. If the Ranger predates 1996, then your vehicle uses Ford's unique Electronic Engine Control, and an OBD-II scanner would be useless. While the two processes are different, both of them are fairly simple to conduct. Either way, retrieving fault codes makes troubleshooting an engine a lot easier.
Locate the Ranger's diagnostic outlet beneath the dashboard. It should be beneath the steering column. Any variations would have it to the right or left of the steering column's underside.
Insert the OBD-II scanner's plug into the Ranger's diagnostic outlet. The next couple of steps are generic. OBD-II scanners differ by brand, both by button configuration and by the process they require to read code. Always consult your scanner's user manual for the exact, precise steps you need to follow.
Insert your key into the Ranger's ignition and turn the electrical system on. If you own a scanner that requires the engine on, crank the Ranger's engine.
Look at the scanner's screen. If your brand of scanner has not self-activated and retrieved the fault codes, turn it on and activate any buttons needed for a "read" or "scan" command.
Consult your scanner's user manual for the fault code descriptions. There are two types of code to consider, generic and manufacturer specific. Generic codes are universal and apply to all OBD-II-compliant cars and light trucks. Manufacturer codes are specific and supplemental. Your manual may not feature the manufacturer codes, but these can be found online rather easily, especially those for Fords.
Start the Ranger's engine and let it warm to its usual operational temperature. Then, turn the engine off. Ensure the air conditioning is off, shift into neutral or park, and engage the emergency brake.
Pop the bonnet and look into the engine compartment. You are looking for a six-sided trapezoidal hub. It will contain six ports. This is the self-test outlet. Next to it, you will find a single access port. This is the self-test input. Connect the two with jumper wire.
Return to the driver's seat and turn the Ranger's electrical system on. Do not crank the engine.
Watch the check engine light. It will begin to flash code at you. Ford EEC codes are either two- or three-number sequences. Count the number of flashes. Small pauses indicate a new number within the sequence. Longer pauses indicate a new coding sequence is about to begin. For example, code 56 will contain five flashes, a short pause, six more flashes and a longer pause before a new code starts.
Write the codes down and search the Internet for a description and definition (see Resource section).