Why won't my Cadillac CT6 auto stop work, or why is it dead after a new battery?

Short answer: A CT6 auto stop that never shuts off the engine usually means one of the manual's conditions isn't met, often battery charge. If the car keeps going dead after a new battery, have a parasitic draw test done. Nav SD card errors often come down to the card's lock switch.

Symptom: The engine never auto stops, the car is dead in the morning, or the screen shows an SD card error.

What to check first

1. Read the auto stop conditions in the owner's manual.
2. Have the battery and charging system tested.
3. If it keeps dying, ask for a parasitic draw test.
4. Check the SD card lock switch; remove it only with the ignition off and the door open.

Likely causes

1. Auto stop conditions not met. Auto stop only works when the battery is charged, the cabin temperature is settled, the engine is warm and other conditions in the owner's manual are met.
2. Parasitic battery drain. Something stays powered after you lock the car and drains the battery. A shop measures the draw and pulls fuses to find it.
3. Navigation SD card locked or loose. The map card has a small lock switch. If it's set wrong or the card was pulled with the power on, the system shows an error.

What it usually costs

Owners didn't post prices. A parasitic draw test is shop time; get a quote.

Is it safe to keep driving?

Auto stop not working is not a safety issue. A car that dies may leave you stranded.

DIY or shop?

Manual checks and the SD card are DIY. Draw testing is easier at a shop.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists 8 recall(s) for the Cadillac CT6 in these years, and none match this problem. Check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• Plain words: The complaint count below shows how often owners reported problems that mention these words to NHTSA. A count is not proof of a defect.
• NHTSA complaints: 6 keyword-matched complaints for Cadillac CT6 2016–2020 (of 77 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-28; keywords: battery, stop start, auto stop, infotainment, screen, display, dead). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In AUTO STOP doesn't turn off engine when cadillac CT6 stops! on Car Talk, a CT6 owner's auto stop never shut off the engine at stops. Members pointed to the owner's manual list of conditions that must be met.
• In 2017 Cadillac CT6 - Battery issue on Car Talk, a 2017 CT6 kept going dead even after a new battery. Members suggested testing for a parasitic draw and checking for a service bulletin.
• In 2020 Cadillac CT6 - Infotainment issue on Car Talk, a 2020 CT6 showed a navigation SD card error. Members said to check the card's lock switch and only remove the card with the ignition off and the door open.

Quick tip

If a new battery didn't fix a dead car, the battery wasn't the problem. Find the drain.

Vehicle focus: Cadillac CT6, 2016-2020.

Safety / mechanic note

Electrical problems can leave you stranded. Verify with a mechanic.