An analog voltmeter must be used to read the codes from the VF terminal of the EFI Service Connector.ĭepending on the vintage of the system being tested, the codes will be displayed in either one or two digit format. On '83 through '85 Cressida and Supra models, the check engine light does not flash diagnostic codes. Low voltage on T causes the ECU to enter diagnostic mode, producing diagnostic codes on the check engine light. When the T terminal is grounded with the ignition switch in the 'on' position, the ECU sees the voltage at terminal T go low. Jumper check connector terminals T (TE1) to E1.Confirm that the throttle is closed (IDL contact on).Turn the ignition switch to the 'on' position and make sure that the check engine light is on.Locate the check connector under the hood and identify the T (TE1 on late model TCCS) and E1 terminals.The E1 ground circuit is also located in the check connector. When grounded, this terminal triggers the self diagnostic feature of the ECU. All engines equipped with self diagnostic systems have one terminal of the check connector identified as T or TE1.

The procedure to examine the ECU memory for diagnostic codes is typically very simple regardless of which vintage engine being diagnosed. Earlier models use this same multiple terminal or a two-terminal check connector, all located under the hood. All late model TCCS applications, from 1988, use a multiple terminal diagnostic check connector. There are several different types and locations of diagnostic connectors which are used to trigger and, in some cases, read diagnostic code output from Toyota EFI engines.

Aristo ecu diagnostic