have an obd2b-obd1 conversion harness but tach in stock guage cluster doesnt work and everything else does, i have looked at the pinouts and cant find which wires to connect, i think the harness is missing the wire for the tach, its not the ecu because it works in another obd1 gsr, can someone please tell me wich pins location to connect as i cant figure it out. its a p72 ecu btw

 

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