Nothing ruins a winter morning like the click-click-nothing of a dead battery. The Blazer has a specific, GM-documented reason this can happen, and if you only replace the battery, you might be back here in a week. Here's how to work it out.
The cold-weather drain GM found
GM bulletin PIT5745B (March 2021) covers a long list of GM vehicles, including the 2019-2020 Blazer, and later versions (PIT5745C and PIT5745D) list the 2021 Blazer. The condition GM describes:
- Dead battery or needing a jump start
- Slow cranking
- Auto Start/Stop not working because the battery's charge is low
- Instrument panel backlighting flickering while the vehicle should be asleep
- Keyless entry or keyless start not working
The catch: it happens when the vehicle sits outside overnight in temperatures below 40°F. GM says that's "critical to reproducing the condition," and it's hard to duplicate in a warm service bay. The cause is one or more modules waking up the low-speed GM LAN network, with the seat memory control module called out as a likely culprit. Dealers confirm it with a parasitic draw test, pull the seat module fuse and watch the draw drop, then replace the module.
Another drain to rule out: Shift to Park
The 2019 Blazer was named in a class action over GM's "Shift to Park" problem, where the car doesn't detect that it's in Park and won't fully shut down. NHTSA complaints from 2019 and 2020 Blazer owners describe that message and the car not turning off. If your Blazer doesn't fully power down, the battery will be flat by morning no matter how new it is. Watch the dash after you shut off. If it says "Shift to Park," that's your drain.
Is it the battery, the alternator, or a drain?
- Battery is several years old and dies once in a cold snap: probably just the battery.
- New battery, still dies after cold nights: think drain (PIT5745 or Shift to Park).
- Battery light on while driving, or dim lights at idle: charging system, have the alternator tested.
- Dies after a few days parked in any weather: have a parasitic draw test done.
Most parts stores test batteries and charging systems for free. Do that first.
The Blazer battery itself
Batteries Plus lists Group 94R AGM batteries for the 2020 Blazer across all three engines (2.0L, 2.5L and 3.6L). AGM matters here. Blazers with Auto Start/Stop need an AGM battery to handle all those restarts, and a cheaper flooded battery can wear out fast and leave start/stop disabled.
What it costs
| Job | Where | Likely cost |
|---|---|---|
| Battery replacement, 2019 or 2023 Blazer | Dealer (KBB, Columbus, Ohio) | $373 to $439 (parts $243 to $286, labor $130 to $153) |
| Battery replacement, 2019 or 2023 Blazer | Independent shop (KBB) | $358 to $422 |
| Group 94R AGM battery only, 2020 Blazer | Batteries Plus | $234.99 to $372.99 listed, plus a $22 refundable core deposit |
| Seat memory module replacement under bumper-to-bumper warranty | Dealer | Usually $0 |
| Parasitic draw test | Shop | Ask for a quote, it's diagnosis time |
What to ask the shop
- "Did you do a parasitic draw test, and what was the reading?"
- "Does bulletin PIT5745 apply to my VIN?"
- "Is the replacement an AGM battery that matches the original spec?"
- "Did you reset the battery monitor after installing it?" (Start/stop systems track battery condition, and a shop scan tool can reset it.)
Is it worth fixing?
Yes. A battery is routine maintenance, and the seat module fix is a known, quick repair. Just don't keep buying batteries for a drain problem. Find the drain once and you're done.
More Blazer repair info is on the Chevrolet Blazer page. Brakes squealing? See our Blazer brake pad cost guide. Prices checked October 14, 2026.
