14 pin Nissan consult ECU connector at the car, front view
Nissan CONSULT-I is Nissan’s proprietary pre-OBD-II ECU diagnostic interface, introduced around 1989 and used on vehicles such as the 300ZX (Z32), 240SX (S13/S14), Skyline, and Maxima through approximately 2000, when Nissan transitioned to the standard OBD-II 16-pin DLC. The 14-pin connector is located near the driver-side fuse box and uses a three-wire bus — a data transmit line (12 V idle-low), an open-collector receive line, and a separate asynchronous clock at 153.6 kHz (16× the 9600 baud data rate). Communication is 9600 baud, 8N1, and a session is initialised by sending the byte sequence 0xFF 0xFF 0xEF.
Notes
- Experimental interface. Terminal programme must send and receive in hex mode.
- The CONSULT-I bus uses three wires: TX (12 V idle, pulled low to transmit), RX (open-collector), and a dedicated clock line at 153.6 kHz — this clock is separate from and not part of the RS-232 serial signal to the PC.
- Initialisation sequence: send 0xFF 0xFF 0xEF to begin a diagnostic session.
- Nissan phased out CONSULT-I by around 2000 in favour of the standard OBD-II 16-pin DLC connector.