Back in the days before check engine light codes could be retrieved by using an OBD scanner, technician had to actually know how to retrieve the codes so that engine problems could be accurately diagnosed. Although technical advances have made it simple to retrieve check engine light codes on current model vehicles, the older cars such as in 1994 Toyota can still be accurately retrieved.
Remove the rubber covers on the connectors diagnostic connectors. The diagnostic connectors are located in the engine compartment or by the kick panel under the dashboard on the passenger side. Refer to the manufacturer's repair manual for the exact position of the diagnostic connector for your particular model 1994 Toyota.
Connect either the TE1 and E1, or the T and E1 terminals in the diagnostic connectors by using a jumper wire. Refer to the manufacturers repair manual to ascertain which terminals should be jumped in and the location of the terminals to be jumped within the diagnostic connector on the particular model being diagnosed.
Turn the ignition key to the "On" position. Any available codes can be determined by observing the flashing of the check engine light. For example, if the engine code is "41" the check engine light will flash four times and pause followed by one additional flash. If there are any additional codes they will be displayed after a 2.5-second pause.
Refer to the 1994 Toyota manufacturer's repair manual to decipher any codes that are retrieved.
Disconnect the jumper wires and replace the rubber covers on the diagnostic connectors by pushing them back over the end of the diagnostic connector.
