1. Weak Battery. If your Compass engine won’t crank or cranks very slowly, then the most likely culprit is weak or dead 12v battery. Investigating more closely and doing a battery voltage test will clarify whether the starting problem is due to the battery. A test can be done to measure the voltage between the battery poles, check the acid The gas engine, the ICE, stops and starts based on battery charge state not vehicle movement. Gas-only vehicles have to have their engines running to move even slowly and stop/start was introduced to eliminate the waste of fuel and emissions during idling and when the vehicle is stopped.
If the air-conditioning needs to run continually to cool the interior, the engine will restart or stay on. In stop-and-go freeway traffic, the engine will most likely remain running to avoid

Another feature with the Subie stop start is that it only activates if you press hard on the brake pedal. If you feather the brakes the car stays running. And no it is not hooked up to the brake lights. You need to depress the brake pedal with some authority to get it to stop the engine.

A bad engine ground is a common problem leading to hard-starting and no-starting conditions. The following test takes a voltage drop reading to locate unwanted resistance in the engine ground path. Disable the ignition or fuel system to prevent the engine from starting during your tests.
The most common symptom of a bad main relay is that you won’t be able to start your car, and nothing may happen when you turn the key. It can also result in a stalling engine while driving, or warning lights on your dashboard. Below, I’ve highlighted a more detailed list of the signs of a bad or failing main relay to look for. 1.
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is start stop bad for engine