Circuit Lake

Electronic Project and Circuit Collection

Automotive Scan Tool

03/09/2012 Category: Automotive, Interfacing, Microcontroller, Project, Renesas

This automotive scan tool uses the Renesas M16C/62P development board to create an interface to the onboard diagnostic (OBD) port in cars. The OBD-II communications standard, defines three standard interfaces J1850 VPW, J1850 PWM and ISO 9141-2. This device was designed ONLY for ISO 9141-2 interface and it has been tested on Subaru & Honda cars.

With this OBD-II interface it is possible to request diagnostic data, freeze frame data, and Diagnostic Trouble Codes (DTCs) from the car’s Electronic Control Units (ECUs). It is also possible to clear the trouble codes, which also turns off the Malfunction Indicator Lamp (MIL), also known as the Check Engine Light.

OBD-II Interface Tools

The user interface for this design uses the three buttons for user input and the 8×2 character LCD display for output. The right button selects the mode of operation. The left and center buttons pick which sensor or DTC to display. The four modes of operation in the system are current power train diagnostic data; power train freeze frame data, diagnostic trouble code (DTC), and clear DTC.

Automotive scan tool features: read and interpret the Power train diagnostic sensor data in “real time”, read and interpret the Powertrain Freeze Frame sensor data, display the active DTCs, and clear the active DTCs and MIL.