If remote start doesn't work at all or only works for 10 seconds then stops check these 16 items:
1) Fuel level must be above 1/2 tank
2) Battery should read 12.5v, and more than 10v under load (test, and trickle charge)
3) Check engine light cannot be on
4) Hood, Doors, & Trunk must be closed entirely
5) Check hood latch & hood open sensors
6) Doors must be locked
7) Ensure there is no other key present inside the vehicle
8) Car must be in "Park"
9) Brake switch inactive (brake pedal not pressed)
10) Hazard lights not on
11) Panic button not pushed
12) System not disabled from previous remote start event
13) Vehicle security alarm not active
14) Ignition in OFF position
15) Sometimes the Body Control Module (BCM) can lose connection with the ECU. A dealer can validate and re-establish the connection. This is a software connection, not physical.
16) Faulty or Failing Body Control Module (BCM). Sometimes these have bad solder joints which causes intermittent issues, once the joint fails entirely you'll know it for sure. Cheap solder is the number one cause. Error code U0140 is common, ECU connection to BCM lost. You may also see parasitic battery drain associated. This was the case with my brand new 2023 hellcat.
For diagnosing any/all issues, I recommend ThinkCar Bi-directional Active/Scanners
$160 model https://amzn.to/3PDJ6X5
$500 model https://amzn.to/4jdsTFX
You will drive for the rest of your life, so it will pay for itself 100x over in diagnostic and repair cost savings.. These scanners can do everything, you can control, actuate, test any system in the car, make the doors lock/unlock, make the seat belt chime come on, etc, just as examples. Remote start will not work if you have any DTC codes, so check that first, then you need to look at the BCM body control module system, the driver/passenger door control modules. Run the tests, look at the logs, and try to find where the issue lies.
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