Attach red cable of multimeter to the In order to run the MCU, it should read a input of the MCU, and attach black cable 3.3V. False reading might caused by short of multimeter to the ground. circuit or open circuit. Measure the capacitor between pin 7 The capacitor value should be 220 uF and ground on the LM2574 switching regulator Measure the capacitor between pin 5 The capacitor value should be 22 uF and ground on the LM2574 switching Ensure the ground is not floated. regulator Measure the inductor value between pin The inductor value should be 330 uH and load on the LM2574 switching regulator Measure the output voltage pin 16 on the The output voltage should read as 12V - OBD-II port 14V. If not the connection is open. Measure the capacitor between pin 8 The capacitor value should be 120 uF and ground on the LM2594 switching regulator Measure the capacitor between pin 7 The capacitor value should be 68 uF and ground on the LM2594 switching regulator Measure the inductor value between pin The inductor value should be 100 uH 8 and load on the LM2594 switching regulator Table : LM2594 test criteria 10.1.6 OBD Port Test Expected Result Make sure pin of the switching regulator is input voltage of switching regulator connecting to the output pin of the OBD-II, use should be 12V - 14V the multimeter to test the output voltage Connect the pin 15 on the microcontroller to The LED should be on when the the pin 14 on the OBD-II signal is transferring to the microcontroller from OBD-II Connect the ground on the OBD-II to the The voltage between two node ground pin on the microcontroller, attach the should be really small, nearly to zero.
Attach red cable of multimeter to the input of the MCU, and attach black cable of multimeter to the ground. In order to run the MCU, it should read a 3.3V. False reading might caused by short circuit or open circuit. Measure the capacitor between pin 7 and ground on the LM2574 switching regulator The capacitor value should be 220 uF Measure the capacitor between pin 5 and ground on the LM2574 switching regulator The capacitor value should be 22 uF Ensure the ground is not floated. Measure the inductor value between pin and load on the LM2574 switching regulator The inductor value should be 330 uH Measure the output voltage pin 16 on the OBD-II port The output voltage should read as 12V - 14V. If not the connection is open. Measure the capacitor between pin 8 and ground on the LM2594 switching regulator The capacitor value should be 120 uF Measure the capacitor between pin 7 and ground on the LM2594 switching regulator The capacitor value should be 68 uF Measure the inductor value between pin 8 and load on the LM2594 switching regulator The inductor value should be 100 uH Table : LM2594 test criteria 10.1.6 OBD Port Test Expected Result Make sure pin of the switching regulator is connecting to the output pin of the OBD-II, use the multimeter to test the output voltage input voltage of switching regulator should be 12V - 14V Connect the pin 15 on the microcontroller to the pin 14 on the OBD-II The LED should be on when the signal is transferring to the microcontroller from OBD-II Connect the ground on the OBD-II to the ground pin on the microcontroller, attach the The voltage between two node should be really small, nearly to zero.