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how to clear obd1?

I have a 1986 ford ranger v6 with trouble codes on air intake temp and engine coolant temp,both are reading -40 degrees. I have replaced both items and want to know how to reset the computer. I unplugged the battery for 2 days but it did not help. Any way to clear code without a scan tool???/
Thank you steveg

-40 degrees is an indication of high voltage returning to the computer from the circuit. Just to let you know, if you unplug either of these sensors completely, you open the circuit and -40 is usually what you will get.
With that said, it is apparent that you have an open circuit somewhere along your lines. You probably have a line cut or bad connection somewhere, not the sensor itself being bad.

With OBD1, codes will set right away when something is apparently wrong. If you can’t clear it by pulling the cable then it isn’t going to clear, and you’re going to have to learn to like it or figure out where your open in the circuit is.

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