1991-1993 Self-Diagnosis Check Connector
for the Mitsubishi 3000GT and Dodge Stealth

by Jeff Lucius

The 1991-1993 self diagnosis check connector is located in the left side of the driver's foot well on the side of the fuse box. The factory provided a black, plastic, snap-on cover for the fuse box and a soft rubber boot for the diagnostic connector. I have been told that the diagnostic connector can be removed from the fuse box. So if you do not see it as shown in the picture below, look around; there is one nearby.

Mitsubishi 1991-1993 diagnostic connector M/T

1991-1993 Self-Diagnosis Check Connector
Pin Function
1 ECM - MPI functions
2 unused
3 ECS control unit
4 ABS control unit
5 Auto-Cruise control unit
6 ELC-4 A/T control unit or unused
7 Air Conditioner control unit
8 SRS diagnosis unit
9 ETACS unit
10 Query - ECS, ABS, ECM, A/T, AC
11 Speed sensor
12 Ground

When pin 10 is shorted to ground (pin 12), the control modules are placed in diagnostic mode and the individual control modules noted can exchange diagnostic data with a scan tool using the dedicated pin. For example, when pin 10 is shorted to pin 12, pin 1 is used by a scan tool to exchange data with the engine control module (ECM). The control modules dump error codes without a scan tool by connecting the ground wire from an analog voltmeter to pin 12 and the positive wire from the analog voltmeter to the dedicated terminal. For example, connect the voltmeter's (-) wire to pin 12 and the (+) wire to pin 1 and then turn the ignition switch to ON (do not start the engine). The voltmeter needle will deflect in a pattern that indicates the diagnostic code(s) for the ECM. If, instead, the voltmeter's (+) wire is connected to pin 7, then the diagnostic code(s) for the air conditioner control module would be indicated by the needle deflections.

References
Chrysler Corporation, 1991, 1991 Powertrain Diagnostic Procedures for Dodge Stealth - 3.0L SOHC/DOHC/DOHC Turbo Electronic Fuel Injection: Part number 81-699-0178, 311 p.
Mitsubishi Motors Corporation, 1991, 1992 Stealth Import Service Manual, Vol. 2, Electrical: Part No. 81-270-2116, various pagination.
MMC ECU Diagnostics - hardware, protocol, software http://mmcd.meditprofi.ru/
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Page last updated June 8, 2003.