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Home/DTC Codes/Fiat/Cronos/2018-2025 1.3L I4 Flex Firefly/U0129
U0129

Lost Communication with Brake System Control Module

2018-2025 Fiat Cronos 1.3L I4 Flex Firefly

Critical SeverityNetworkGeneric (SAE)

Description

Cannot communicate with the general brake system control module.

Symptoms

  • Brake warning light on
  • ABS disabled
  • Stability control off
  • Brake system message displayed

Common Causes

  • Brake module failure
  • CAN bus wiring damage
  • Module power loss
  • Fuse blown
  • Water damage

Diagnostic Steps

  1. Check brake system fuses
  2. Test module power and ground
  3. Check CAN wiring
  4. Inspect module for water damage
  5. Try direct module communication

Repair Notes

Check fuses and power supply. Inspect for water damage near brake module location.

Related Codes

U0121Lost Communication with ABS ModuleU0128Lost Communication with Brake Boost Control Module

Other Network Codes

U0129 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 U0129 mean on a 2018-2025 Fiat Cronos?

U0129 stands for "Lost Communication with Brake System Control Module". Cannot communicate with the general brake system control module.

What are the symptoms of U0129 on a Fiat Cronos?

Common symptoms of U0129 include: Brake warning light on, ABS disabled, Stability control off, Brake system message displayed.

What causes U0129 on a 2018-2025 Fiat Cronos?

Common causes of U0129 include: Brake module failure, CAN bus wiring damage, Module power loss, Fuse blown, Water damage.

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