Good day. I am owner of 2016 Q50 20t AWD.

I have problem with idle start/stop (appear : start/stop failure , flash green indicator on dash and Eco bottom with yellow light.)

I have visited Infiniti Service, they made computer diagnostic and found one deficiency: “ENGINE RESTART BYPASS RELAY”. They erased this error and it’s temporarily solved the problem, but after 5-6 times idle the start/stop error appears again (already they have erased it 3 times and not found any reason of this problem). Does anybody know what can be the reason for this problem and how to fix it?

I assume this was storing a P117A or P117B code? The code error, from what I see via the 3.7l Q50 FSM, is "ECM detects a lean/rich air fuel ratio state in any cylinder for a specified length of time". Possible causes are listed as:

• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Mass air flow sensor
• Intake air leaks
• Lack of fuel
• Incorrect PCV hose connection
• Improper spark plug
• Insufficient compression
• The fuel injector circuit is open or shorted
• ignition coil
• The ignition signal circuit is open or shorted

There are quite a large number of diagnostic steps available to walk through in order to try and find out what is causing the issue. That's assuming troubleshooting the 2.0t is similar to the 3.7.

Take it back and have them re-diagnose the problem