- Vehicles
- Cars
U0100
Chevrolet U0100: lost communication with ECM/PCM
Evidence linked to this decision
View source: GM TSB 08-07-30-021G GMLAN communication DTC U0100Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
A module lost communication with the engine/powertrain controller; the reporting module and companion network codes decide where diagnosis starts. Reduced steering assist or no-start is a stop; otherwise power history, reporting module and network evidence come before any module replacement.
Safety first
Stop and check this first
- Do not reproduce a fault on the road. Stop driving for a flashing engine light, severe power loss, smoke, fuel smell, overheating, abnormal mechanical noise, no-start or reduced steering assist.
Safe checks you can perform
- Preserve the evidence before any reset
- Use the observation that changes the path
- Test the official bulletin boundary
Leave these tasks to a qualified professional
- Do not attempt this professional task: Request a measurement-led diagnosis
- Do not attempt this professional task: Trax steering-module latch or BCM circuit case
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Request a measurement-led diagnosis
What they doRun the GM vehicle and high-speed network checks, identify the reporting module and isolate voltage, wiring or terminal faults before replacing any controller.
Trax steering-module latch or BCM circuit case
What they doAsk which module stored U0100, network voltages/resistance under the approved procedure and the exact failed circuit or terminal.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Preserve the evidence before any reset
Save U0100, every accompanying DTC, freeze-frame values, readiness state and the module that reported it. Record the VIN, model year, engine, market and symptoms. Do not clear codes or disconnect the battery yet.
Do not reproduce a fault on the road. Stop driving for a flashing engine light, severe power loss, smoke, fuel smell, overheating, abnormal mechanical noise, no-start or reduced steering assist.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
Use the observation that changes the path
The module storing U0100, all U-codes, no-crank/shift/steering symptoms and recent battery/electrical work are recorded
Do not reproduce a fault on the road. Stop driving for a flashing engine light, severe power loss, smoke, fuel smell, overheating, abnormal mechanical noise, no-start or reduced steering assist.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
Test the official bulletin boundary
2017-2022 Chevrolet Trax with U0100 stored in the power-steering module for TSB 20-NA-206, or a vehicle explicitly listed in GM 08-07-30-021G
A matching code is not enough: every model, engine, market and build condition must match.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Virtual technician
Does U0100 still appear after these checks?
This guided flow uses the exact code and your answers to choose a test, an expected result and the next branch.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Vehicles
- Brand
- Chevrolet
- Product type
- Cars
Known code variants
- Chevrolet U0100
- U0100 Chevrolet
- U0100 code Chevrolet
What it means
GM documents a latched PSCM code after low battery/electrical work and a separate circuit-5985/BCM condition in the exact Trax scope. GM lists chafed wiring, backed-out terminals, opens, shorts, corrosion, water intrusion and connector contact faults before module replacement. 2017-2022 Chevrolet Trax with U0100 stored in the power-steering module for TSB 20-NA-206, or a vehicle explicitly listed in GM 08-07-30-021G
Warnings and stop conditions
- Highsource verified
Do not reproduce a fault on the road. Stop driving for a flashing engine light, severe power loss, smoke, fuel smell, overheating, abnormal mechanical noise, no-start or reduced steering assist.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
Symptoms and causes
Probable causes · in order
- Trax steering-module latch or BCM circuit casePossible
GM documents a latched PSCM code after low battery/electrical work and a separate circuit-5985/BCM condition in the exact Trax scope.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
- high-speed network wiring/terminal faultPossible
GM lists chafed wiring, backed-out terminals, opens, shorts, corrosion, water intrusion and connector contact faults before module replacement.
Evidence: GM TSB 08-07-30-021G GMLAN communication DTC U0100 · GM TSB 20-NA-206 Chevrolet Trax U0100
Sources and technical references
- 1
GM TSB 08-07-30-021G GMLAN communication DTC U0100
General Motors LLC · 2012 · service_bulletin
- 2
GM TSB 20-NA-206 Chevrolet Trax U0100
General Motors LLC · 2022 · service_bulletin
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