U0100: Lost Communication With ECM/PCM A
A generic network and communication trouble code, same meaning on every brand.
If running, drive minimally - communication loss with the engine module can escalate to no-start without notice.
Symptoms
- Multiple warning lights at once
- Gauges dead or frozen
- Stalling or refusal to start
Likely causes, most common first
- CAN bus wiring damage - rodents, chafe, water intrusion
- Failing module dragging the network down
- Power or ground loss to the engine computer
Read U0100 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
U0100 means other computers lost contact with the engine control module on the car's internal network. The engine module is the network's most important citizen; silence from it lights up the whole dashboard.
Network faults reward methodical electrical diagnosis and punish parts-swapping - a chafed pair of twisted wires can imitate a dead thousand-dollar module. Rodent damage deserves particular suspicion on cars parked outdoors: soy-insulated harnesses are apparently delicious.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning U0100
“The contact owns a 2020 Chevrolet Silverado 1500. The contact stated that while driving at approximately 40 MPH, the vehicle shuddered and downshifted independently. No warning lights illuminated. Additionally, an OBD2 diagnostic scan retrieved diagnostic trouble codes: U0146, U0101, and U0100. A local dealer was contacted; however, the vehicle was not diagnosed or repaired because the VIN was not included in any recall. Additionally, the contact related the failure to NHTSA Campaign Number: 24V797000 (Power Train). The manufacturer was not made aware of the failure. The failure mileage was approximately 84,000.”2020 Chevrolet Silverado 1500 · Jul 2026 · 84,000 mi
“Failed emissions test.engine control module error codes,U0129 lost communication with brake system control module,codeU0146 lost communication with serial data gateway module,codeU101lost communication with transmission control module...next failure brake control system module,code U146 lost communication with serial data module, U0100 lost communication with engine control module, U101 lost communication with transmission control module”2019 Chevrolet Silverado 1500 · May 2026
“had a recall done in February and 3 weeks later the car would not start randomly no warning lights illuminated on the dash prior to being shut off and once it would start it threw 3 codes for p0850, u0100, and U1267 all related to the parts replaced in February for the recall for the 2nd time now regarding the same parts. and trying to get a reinspection done for the recall bc the parts seem to have failed and its been a living nightmare. and unsure why no warning lights were illuminated prior to the car not starting randomly”2018 Jeep Grand Cherokee · Apr 2026
Show 7 more owner reports
“2017 Buick envision failed an annual smog check with OBD trouble codes: P0700; P2535; and U0100. P0700 is related to a transmission issue.”2017 Buick Envision · Jan 2026
“No crank no start however engine just shit down while driving immediately lost all control of vehicle! Luckily I had just pulled off highway! No warning whatsoever it just happened out of no where now won't start and has a u0100 code”2007 Chevrolet Silverado 1500 · Aug 2025
“My safety & the safety of others was at great risk while driving my 2018 dodge charger sxt. While driving my dashboard lights went completely dark and the steering wheel locked. I was unable to move out of lanes threatening my life and the life of others around me. Independent mechanic put scanner in my car days later and code that appeared was "U0100 Lost Communication With ECM/PCM" I looked up my vin # on mopar.com and noticed my vehicle did have a "Important Safety Recall: Reprogram Powertrain Control Modulel"”2018 Dodge Charger · Sep 2024
“The problems listed in my vehicle are the following - U0073: Control Module Communication Bus A Off - U0100: Lost Communication With Engine Control Module - U0121: Lost Communication with Electronic Brake Control Module - U0140: Lost Communication With Body Control Module - P0700: Transmission Control Module Requested MIL Illumination I believe this is due to a bad design in the wiring. Also the electric brake vacuum broke which is a common problem.”2020 Chevrolet Malibu · Jul 2024
“Transmission control module Shifting goes into limp mode and doesn't allow acceleration until the car is turned off and back on There are other years of my vehicle where this is an active recall. The transmission service required light comes on Codes are as follows PO776 C1560 U0114 U0100”2016 Mitsubishi Outlander · Jan 2024
“I was driving along I55 at 65-70 mph when my car had multiple lights come on the dash w d started ringing. My car then shot left into the median wall. It spun at least twice hitting the wall and stopping facing southbound in the northbound lanes. The vehicle is currently at the ins inspection lot. The code was u0100. ECM/PCM 'A" DTC. I was injured in the accident and concerned about safety of others”2022 Nissan Altima · Jul 2023
“Car went crazy one day while behind the wheel everything malfunctioned then car shut off and won't start again. I could of easily got into an accident had there been any other vehicles around. Kids were scared. Codes come up as U0100,U0140,U0101,C0242,B0081-0F,B0081-71,B1370-01,B1370-06,U0155-00,U0170-00,P0856-00.”2008 Cadillac CTS · Jul 2023
Cars that report U0100 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with U0100?
If running, drive minimally - communication loss with the engine module can escalate to no-start without notice.
How much does it cost to fix U0100?
Typical US repair costs range from $120 for the simplest fix (wiring/network diagnosis) to $2,000 in the worst case. The right number depends on which cause your car has - see the causes list.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.