U1700 on Fiat — The engine will not start and several electrical systems are unresponsive

Code U1700 reports a loss of CAN bus communication with the body computer. On the Fiat 500 1.2 8v the engine will not start and the electric windows, indicators and tailgate are all out of action.

System

Electronics

Component

Body computer

Fault

The engine will not start, having cut out suddenly while driving, and the hazard lights flash while starting is attempted.

Typical symptoms

• The engine will not start
• The engine cuts out suddenly while driving
• The hazard lights flash while starting is attempted
• Electric windows, indicators and tailgate not working
• Engine warning, airbag, general fault and Start&Stop lights on

Vehicles affected

• Fiat 500 1.2 8v

Main code

• U1700 CAN data bus, body computer, fault and loss of communication

Related codes

• B1010 Brake pedal switch, malfunction
• B1011 Left rear brake light, wiring fault
• B1017 Door locking relay, wiring fault
• B1023 Number plate lights, wiring fault
• B1028 Right rear brake light, wiring fault
• B1048 CITY switch, malfunction
• B1057 Driver's side window switch, fault
• B1058 Passenger's side window switch, fault
• P0504 Brake switch 1-2 correlation, incorrect relationship
• P181D Gear lever position sensor, neutral position, incorrect signal
• U0422 Active suspension control unit, invalid data received
• U0426 Auxiliary heater control module, invalid data received

On this fault the diagnostic tool often returns several codes together.

Solution

See the repair procedure verified on Sema Repair.

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