U0100 on Cadillac
Lost Communication with ECM/PCM
U0100 on Cadillac vehicles indicates lost communication with ecm/pcm. Au7o has documented this code across 1 Cadillac model — most commonly on ELR. U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable.
Common Causes of U0100
- •Loss of power or ground to the ECM/PCM
- •CAN bus wiring damage, short, or open circuit
- •Corroded, loose, or damaged connectors at the module
- •Blown fuse feeding the ECM/PCM
- •Failed ECM/PCM
- •Another faulty module pulling down the data bus
- •Water intrusion or corrosion in a connector/harness
U0100 on Cadillac by Model
Cadillac ELR(1 issue)
- Low 12-Volt Battery Can Prevent Module Wake-Up; Diagnose the Cause First2014-2015
A low ELR 12-volt battery can leave control modules unable to wake and prevent a normal start. GM also issued VIN-gated program 14395A for a bounded 2015 OnStar-module battery-drain condition; that program expired in 2017 and is not proof of a universal drain.
Looking for U0100 on a different make?
View U0100 across all makes →Frequently Asked Questions
What does U0100 mean on Cadillac?▼
U0100 stands for "Lost Communication with ECM/PCM." U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable. On Cadillac specifically, this code is documented across 1 model.
What causes U0100 on Cadillac vehicles?▼
Common causes on Cadillac: Loss of power or ground to the ECM/PCM, CAN bus wiring damage, short, or open circuit, Corroded, loose, or damaged connectors at the module, Blown fuse feeding the ECM/PCM, Failed ECM/PCM. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U0100 on a Cadillac?▼
Repair costs vary widely depending on the root cause and specific Cadillac model.
Which Cadillac models have U0100 documented?▼
Au7o has documented U0100 on 1 Cadillac model: ELR.