Chevy Check Engine Code
U0100 on Chevy
Lost Communication with ECM/PCM
Also covers: Chevrolet, GMC, Buick, Cadillac, GM
U0100 on Chevy: what makes it different
U0100 (lost communication with ECM/PCM) is frequently reported on Chevy trucks and SUVs where CAN bus wiring runs near the engine mounts, exhaust, or firewall grommet and is prone to chafing or corrosion over time.
Most-affected engines
- LS-series V8 (Silverado, Tahoe, Suburban)
- Ecotec 2.0T/2.4L I4 (Equinox, Malibu)
- LFX 3.6L V6 (Traverse, Malibu)
Common model years: 2007–2018
Most likely cause on Chevy
A chafed, corroded, or loose CAN bus wiring connection between the ECM and body control module, often at a harness routing point near the engine or firewall.
Known Chevy engine-family issues
Some V8 trucks have harness routing points near the engine mount or exhaust crossover where wiring insulation can wear thin over years of heat and vibration, and battery terminal corrosion is a common low-cost cause of intermittent communication loss.
Chevy-specific causes (most common first)
- Chafed CAN bus wiring rubbing against a bracket or exhaust component
- Corroded or loose ECM/BCM connector pins from moisture intrusion
- Weak battery, corroded terminals, or poor grounds causing voltage dips that drop communication
- Aftermarket alarm, stereo, or accessory wiring improperly tapped into the CAN bus
- Internal ECM connector or module fault after long-term wear
Chevy-specific diagnostic tip
Start with a voltage drop test on the battery and ground connections, since low voltage alone can trigger U0100; if that's clean, visually trace CAN high/low wiring near engine mounts and the firewall pass-through for chafe or corrosion before considering an ECM fault.
Symptoms drivers report
- Multiple warning lights
- No-start or intermittent stalling
- Dashboard gauges blank or erratic
- Limp mode
Typical repair cost on Chevy
Most Chevy owners fix U0100 for between $150 and $900, depending on which underlying cause turns out to be at fault. Start with the most-likely cause for your vehicle — A chafed, corroded, or loose CAN bus wiring connection between the ECM and body control module, often at a harness routing point near the engine or firewall. — before throwing parts at it.
Chevy U0100 FAQ
Is U0100 always an ECM problem on my Chevy?
Not usually. It's more often a wiring, connector, or battery/ground issue interrupting communication rather than the ECM itself failing.
Why does U0100 come and go intermittently on some Chevy trucks?
Intermittent chafed wiring or a marginal ground connection can cause the CAN signal to drop only under vibration, heat, or specific driving conditions, which is why the code isn't always present.
Related codes
Drive a different make? See the general U0100 guide for cross-vehicle causes and symptoms.
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