The symptoms of a bad ground strap are flickering lights, low voltage readings, battery warning light coming on, electrical malfunctions that can be intermittent across the vehicle and even sometimes difficulty in starting the car or a dead battery.
The symptoms of a bad ground strap on a vehicle can vary and may not always show all these symptoms and may only cause some of these symptoms or only one or a few.
If you have a good ground wire otherwise you may still have a proper charging battery from the alternator and may still be able to start your vehicle with no issue.
A bad ground strap could cause you to fry ignition control modules, lead to voltage fluctuations, may cause static in the radio and could cause interference with other electronics in the vehicle.
Headlights or other lights on or in the vehicle may flicker with a bad ground strap as a result of inconsistent power supply that is caused by a poor ground connection.
In some cases the bad ground strap may prevent the alternator from properly charging the battery.
A bad ground strap may also cause low voltage readings and sometimes the other electrical components of the vehicle such as the AC compressor clutch may not work properly or the windshield wiper motor or window motors etc may not work properly or intermittently as a result of a poor ground connection from the ground strap.
The dashboard battery warning light may also illuminate due to issues with the charging system due to a bad ground strap as well.
It's always better to have more ground straps than too little or no ground straps at all.
There should always be a ground strap from the engine to the firewall and even from the engine to the frame if you vehicle has a frame.