U0100 Chevrolet Code - Lost Communication With Engine Control Module

That U0100 means the other control modules are losing communication with the ECM. On the 2014 Impala with the 2.5L, that can be caused by a weak battery, poor ground, or corrosion at the main ECM connectors or underhood fuse block.

When the engine stalls right after starting and sets U0100, it’s often a power or ground issue rather than a bad ECM. I’d start by checking battery voltage (should be 12.6V off and over 14V running), then inspect and clean the main grounds—especially the one near the transmission and the one on the radiator support. Also look for water intrusion or corrosion around the ECM connectors.

If power and grounds check out, then it’s worth having the CAN network checked for intermittent opens or shorts, but in most cases cleaning and securing the connections fixes it.

All of those codes together point to a low voltage / power distribution problem, not a bad alternator.

11.67 volts is already too low for a modern GM to behave normally. These cars get very picky once battery voltage drops under about 12.2 V. When the voltage is low or unstable, modules start dropping off the network — that’s why you’re seeing U0100 (lost ECM), U0121 (lost ABS), U0401 (invalid data), and C0299. They’re symptoms, not separate failures.

Even though the parts store said the battery is “good,” a battery can pass a quick test and still collapse under load. At 11.67 V sitting, it’s either discharged, sulfated, or there’s a bad connection somewhere.

Before replacing more parts, I’d focus on the basics:

• Fully charge the battery with a charger (don’t rely on driving to charge it)
• Load-test the battery with a proper tester, not just a quick scan
• Inspect battery terminals for corrosion or looseness
• Check the main engine ground and body ground cables
• Check voltage drop from battery to fuse block while cranking
• Inspect the underhood fuse block for loose or overheated connections

If voltage drops too far when you hit the key, the ECM shuts down and the car won’t start — exactly what you’re seeing.

Most no-start U0100 cases on these Malibus end up being:
a weak battery,
a bad ground,
or a power feed issue at the fuse block.

I’d start there before suspecting the ECM itself. Once stable voltage is restored, a lot of those codes usually disappear on their own.

When a newer Traverse throws U0100 along with AWD, parking brake warnings and unstable idle, you’re usually looking at a communication or voltage problem, not a single bad part.

U0100 means modules are intermittently losing contact with the ECM. When that happens, other systems (AWD, ABS, parking brake, etc.) go into fail-safe and start throwing warnings.

The fact that it starts and then acts up is important — that usually points to something dropping out after startup.

On a 2023, the most common things I’d check first are:

• Battery condition and voltage stability – even a weak battery or bad connection can cause all of this
• Battery terminals and grounds – make sure they are clean and tight
• Underhood fuse box connections – loose or poor contact can cause intermittent module dropouts
• Software updates – newer GM vehicles sometimes have updates for communication/network issues
• Wiring/connectors at the ECM – especially if anything was recently serviced

The idle jumping up and down is likely the ECM losing and regaining control, not a true engine problem.

Since this is a 2023, I would strongly recommend having the dealer check it while under warranty. This kind of issue is often handled with software updates or fixing a connection issue, and you don’t want to chase it on your own if it’s covered.

Bottom line: multiple systems acting up at once = shared power/communication issue. Start with battery, grounds, and connections, then let the dealer handle deeper diagnostics if needed.