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Q: When weather gets hot, SUV randomly won't start

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My SUV will randomly not start when the weather gets warmer. All of the following shut off: brake light, ABS light, security light, and radio. After waiting for 20-30 minutes, then my SUV will start. I have replaced the following: fuse block, ECM Module & reprogram, switch key Vincut key, BCM module (twice), mass air flow sensor. Plus, reprogrammed the security system (twice), greased the ground wires, and grease on terminals fuse block. I’ve been to the dealership and to two mechanic shops and have spent a lot! My car has not been fixed yet! What is your diagnosis and can you suggest what is causing the problem?

Hello. This sounds like an issue that would be difficult to diagnose online without inspecting the vehicle. I’m thinking that if you have replaced the ECM module and reprogrammed it, as well and the BCM module, fuse block, and mass airflow (MAF) sensor, it is possible that the engine wiring harness may have broken or frayed wiring, which is causing this intermittent problem.

If the coolant temperature sensor is sending the wrong reading to the ECM, it is also a possibility that the coolant temperature sensor could be faulty and causing this problem as well. A temperature reading that is incorrect may cause the ECM to make incorrect adjustments for the fuel/air mixture which may cause hard starts. I would suggest that you have a certified technician, like one from YourMechanic, come and inspect your vehicle to make a proper diagnosis on your car’s no-start.

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