How do I check trouble codes on my 1992 Mercury Topaz XR5?
If you have an analog volt/ohm meter, the code numbers can be retrieved by counting the sweeps of the needle on the meter.
If you don’t have an analog volt/ohm meter, then you need a code reader such as this. And if you page down, you’ll see what the diagnostic connector looks like under the hood. Sometimes it’s located under a plastic cover labeled TEST.