Engine system fault message

[stephen.howard3]

Whist trying to jump start my Focus, the jump leads were briefly connected to the wrong terminals whilst connected to the battery in my other car. Now the engine system fault message is displayed and the engine will not turn over. Is there anyway I can fix this issue myself?

[Luke4efc]

Most likely blown ECU fuse. If not check all the other fuses.
Failing that then you could've blown the ECU itself.

2 minutes or 2 seconds, it still does the same damage lol.

[dezwez]

pray its the ECU fuse never connect the wrong way  ☹️

[Kevin#95]

Check the 5v reference voltage coming out of the ECU. Unplug the throttle position sensor or mass air flow sensor and with the ignition key turned on you should see 5v on one of the pins. If you dont see the 5v it probably means the ECU is bad. Use a meter set to 20v DC and hold the red lead gently on the pin with the black lead to an earth. Dont push the probe into the pin, just touch it gently. If you see 5v it is a good sign the ECU is ok.

[Kevin#95]

Might be worth checking all the fuses. The ECU should be protected by the fuses. Other fuses may have gone. On some fuses you can see the fuse wire so you dont need to check it if it's not blown.