Procedures to Retrieve Trouble Codes - Toyota Engine Control Systems (toyotaguru.us) Don't know if this will help you. If you can obtain a service manual it will give step by step how to retrieve any codes. On my '91 there is a port under the hood close to the firewall on the driver side, little flip up plastic cover. A bent paperclip in the right contact points will show readouts with a blinking cel on your dash. Don't know if this is the same on your '88.
It does have an OBD port on it. My 89 has it on the driver side near top of the engine bay. It says Diagnostic on it. But as far as I can find no handheld diagnostic reader will work with it. Even though they came with the Toyota OBD connector. But the easier way to pull codes is like Sea-J wrote take a paper clip and connect pins E and T1.