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The vehicle should have an OBD port under the hood. See pic 1. Is that what you are referring to? As far as retrieving codes, it just requires a jumper wire. Also, here are the directions for testing. Pictures 2 and 3 correlate with the directions.
Let me know if this is what you are doing. Also, what is in bad condition?
Retrieving Data Trouble Codes In Normal Mode
picture 2
Retrieving Data Trouble Codes In Test Mode
picture 3
DESCRIPTION
The Data Link Connector is used to trigger the self diagnostic capabilities of the Engine Control Module (ECM).
OPERATION
By connecting the Data Link Connector terminals with a jumper wire as shown, the ECM will begin to indicate any stored Data Trouble Codes for either normal or test modes.
Let me know if this helps or if you have other questions. Also, here is a link you may find helpful. Not only does it show how to retrieve OBD 1 codes, but provides a list of codes to help determine problems.
https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995
Take care,
Joe
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Tuesday, April 16th, 2019 AT 10:32 AM