U1900 Manufacturer-specific Basic entry

CAN Communication Bus Fault

Updated 2026-10-10 · Network (manufacturer-specific)

Severity

Medium

Typical repair cost

50 – 700 EUR

System

Network

This is a manufacturer-specific code. Its exact meaning can differ between makes; the definition below follows the most common usage.

What it means

U1900 indicates a fault on the vehicle communication bus itself rather than in one component: CAN Communication Bus. Several modules may log related codes at the same time.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

Several warning lights on at the same time
Functions controlled by the affected module do not work
Scan tool cannot communicate with one module
Gauges dropping to zero or dashboard flickering

Common causes

Blown fuse or no power supply to the CAN Communication Bus
Poor ground for the module
Damaged CAN/data bus wiring or connector
Failed module
Low battery voltage during cranking or after a jump start

How to diagnose

Check which modules respond to a full system scan and which do not
Verify fuses, power and ground at the CAN Communication Bus connector
Measure CAN bus resistance between the two bus wires (about 60 ohms with the battery disconnected) and inspect the wiring
Check battery voltage and charging system; low voltage causes many communication codes
Replace or reprogram the module only after power, ground and bus wiring are confirmed

Frequently asked questions

Can I keep driving with U1900?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing U1900 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.