U0100 on Chrysler: How to Diagnose & Fix
Lost Communication with ECM/PCM
1 Chrysler model · 1 documented issue · 1 critical
U0100 on Chrysler by model: symptoms, diagnosis and fix
On Pacificas built with the engine stop/start system, sealer left on the wire-harness tab during harness manufacturing sits inside the battery ground joint. Over time the sealer creeps and the joint loses clamp load, so the main chassis/engine ground goes intermittent. The high current draw of stop/start restarts makes it worse. Drivers get sudden electrical dropouts: the engine stalls at speed, electric power steering assist cuts out, and a cluster full of warning lights appears. FCA recalled 198,731 vehicles (NHTSA 19V-348, FCA campaign V53).
Common Symptoms
- Engine stalls while driving
- Sudden loss of power steering assist, heavy steering
- Multiple warning lights flash on the cluster
- Stop/start system faults or will not re-fire
- No-crank or intermittent no-start
How to Fix
Have the recall performed: the dealer disassembles the battery ground joint, cleans the contact surfaces and the harness tab of sealer, and reassembles the ground to correct clamp load, free of charge. Out of warranty or if symptoms return, remove the negative battery ground bolt, clean all mating surfaces to bare metal, and torque to spec; inspect the engine-to-body ground strap at the same time. A weak or failing AGM battery amplifies the same symptoms and should be load-tested.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (3)
U0100 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0100 mean on a Chrysler?
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 Chrysler it is documented across 1 model: Pacifica.
What are the most common causes of U0100?
The most common causes of U0100 are: 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. The specific cause varies by vehicle.
How much does it cost to fix U0100 on a Chrysler?
Repair costs vary widely with the root cause and Chrysler model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.