U0100 – Lost communication with the engine computer

Lost communication with ECM/PCM A

Network and modules · generic OBD-II code

Short trips only

Drive it only if you have to, gently and not far. Get it fixed right away.

Check this first

Check the battery terminals and grounds – weak power causes more of these than broken wires do.

What usually fixes it

In the order a good shop checks them. Typical total: $114–$1,906 at $130 an hour.

$114–$512

Battery, terminals and grounds

Low or dirty power makes modules drop off the network.

$258–$725

Network wiring

A damaged wire between modules.

$660–$1,906

Engine computer

A module that has genuinely failed.

What the vehicle can tell you itself

A stored code is a headline, not the story. The vehicle also holds the conditions when it happened, how close the part is to the limit it fails at, what the fuel trims are doing, and whether the fault is still happening right now. Drive DTC reads all of it with a USB adapter and a Windows PC – and it can't change a single setting on the vehicle.

See what your vehicle says about U0100

Codes in plain English, what usually causes them, what the repair costs, and whether it's safe to drive.

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