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Home/DTC Codes/Fiat/Cronos/2018-2025 1.3L I4 Flex Firefly/U0100
U0100

Lost Communication with ECM/PCM

2018-2025 Fiat Cronos 1.3L I4 Flex Firefly

Critical SeverityNetworkGeneric (SAE)

Description

The diagnostic system cannot communicate with the Engine Control Module.

Symptoms

  • Multiple warning lights
  • Engine may not start
  • Many systems inoperative
  • Cannot read engine codes

Common Causes

  • PCM power or ground failure
  • CAN bus wiring issue
  • PCM failure
  • Fuse blown
  • Wiring harness damage

Diagnostic Steps

  1. Check PCM fuses
  2. Test PCM power and ground circuits
  3. Check CAN bus wiring to PCM
  4. Try communicating with other modules
  5. Inspect wiring harness

Repair Notes

Check fuses and power supply to PCM first. CAN bus issue is second most common.

Related Codes

P0600Serial Communication LinkU0001High Speed CAN Communication BusU0101Lost Communication with TCM

Other Network Codes

U0100 on Other Vehicles

Fiat 124 Spider

2017-2020 1.4L I4 Turbo

Fiat 126p Maluch

1973-2000 0.65L I2 Air-Cooled

Fiat 126p Maluch

1987-2000 0.7L I2 Air-Cooled

Fiat 500

2012-2019 1.4L I4

Fiat 500 Abarth

2012-2019 1.4L I4 Turbo

Fiat 500 BR

2011-2020 1.4L I4 Flex Fire Evo

Fiat 500 PL

2007-2025 1.0L I3 Hybrid FireFly 70

Fiat 500 PL

2007-2025 1.2L I4 Fire 69

Common Questions

What does code U0100 mean on a 2018-2025 Fiat Cronos?

U0100 stands for "Lost Communication with ECM/PCM". The diagnostic system cannot communicate with the Engine Control Module.

What are the symptoms of U0100 on a Fiat Cronos?

Common symptoms of U0100 include: Multiple warning lights, Engine may not start, Many systems inoperative, Cannot read engine codes.

What causes U0100 on a 2018-2025 Fiat Cronos?

Common causes of U0100 include: PCM power or ground failure, CAN bus wiring issue, PCM failure, Fuse blown, Wiring harness damage.

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