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2021 CT4 2.7T Battery Drain / No Start After Sitting

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Sarah K. · rep 0 · May 22, 3:56 AM · 1 replies · solved · Question

Vehicle: 2021 Cadillac CT4 Premium Luxury 2.7T

Hey forum,

I'm having a persistent battery drain issue with my 2021 Cadillac CT4 2.7T. If the car sits for more than 24-36 hours, the battery is completely dead, and I get a 'No Start' condition. I've had to jump-start it multiple times now.

The battery itself is relatively new (replaced about 8 months ago), and I've had it tested, and it shows good health. I'm not leaving any lights on or accessories plugged in.

Could this be a parasitic draw, or maybe an alternator issue? What's the best way to track down what's draining the battery on these newer Cadillacs? No check engine lights are on currently.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:56 AM

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ClearTheCode admin answer:

A recurring battery drain on a 2021 Cadillac CT4, especially with a relatively new and tested battery, strongly suggests a parasitic draw or an issue with the charging system. Since you have no check engine lights, it's less likely to be a direct sensor fault, but rather an electrical component not shutting down properly.

  1. Initial Checks:

    • Battery Terminals: Ensure both battery terminals are clean and securely tightened. Loose or corroded terminals can prevent proper charging and discharge.
    • Alternator Output: While the battery is good, the alternator might not be charging it sufficiently. With the engine running, use a multimeter to check the voltage across the battery terminals. It should read between 13.5V and 14.8V. If it's significantly lower, the alternator or its regulator might be failing.

  2. Testing for Parasitic Draw (DIY Method):

    • Multimeter Setup: Disconnect the negative battery cable. Connect a multimeter in series between the negative battery post and the disconnected negative battery cable. Set the multimeter to measure amps (A or mA).
    • Establish Baseline: After connecting, the initial draw might be high as modules wake up. Wait at least 15-30 minutes for all vehicle systems to 'go to sleep.' A normal parasitic draw should be below 50mA (0.05A) for most modern vehicles.
    • Isolate the Circuit: If the draw is high, start pulling fuses one by one from the fuse box (both under the hood and inside the cabin) while watching the multimeter. When the amperage drops significantly, you've found the circuit responsible. Consult your owner's manual for the fuse diagram to identify the components on that circuit.

  3. When to See a Shop:

    • If you're uncomfortable performing the parasitic draw test, or if you identify a circuit but can't pinpoint the specific component (e.g., a module that isn't shutting down), a professional diagnostic is recommended. Modern vehicles have complex electrical systems, and a shop with advanced diagnostic tools can more efficiently trace the source of the draw, which could be a faulty body control module (BCM), infotainment system, or another electronic component.
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