U1900 on Saab: How to Diagnose & Fix
CAN Communication Bus Fault
1 Saab model · 1 documented issue · 1 critical
U1900 on Saab by model: symptoms, diagnosis and fix
Second-gen 9-3 (2003-2011) sunroof drains clog with debris (pollen, leaves). Water then overflows into the headliner, runs down the A-pillars, soaks the carpet, and pools in the front footwell — directly under the DICE (Driver Information Central Electronics) and TWICE modules. Wet modules can short and cause a cascade of weird electrical faults (no-start, dead instrument cluster, ABS faults, etc.).
Common Symptoms
- wet carpet
- no-start intermittent
- dead dash
- multiple electrical warnings
- mildew smell
How to Fix
Clear sunroof drains annually (compressed air from above, fishline gently from below). If carpet is wet, dry IMMEDIATELY — remove driver carpet and inspect the modules. Once a module is corroded the only fix is replacement and recoding ($300-$1,200). Aftermarket dehumidifier packs in footwell help in humid climates.
U1900 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 U1900 mean on a Saab?
U1900 stands for "CAN Communication Bus Fault." U1900 is a manufacturer-specific network code (commonly Ford) indicating a CAN communication bus fault, often a receive error. The CAN bus is the high-speed network that lets control modules such as the powertrain computer, ABS module, and instrument cluster share data. This code is set when a module stops receiving expected messages from one or more modules on the bus. Because so many systems depend on the network, a bus fault can trigger multiple warning lights and erratic behavior across systems. On Saab it is documented across 1 model: 9-3.
What are the most common causes of U1900?
The most common causes of U1900 are: Damaged, corroded, or loose CAN wiring/connectors, A failed or offline module pulling down the bus, Short to power or ground on a CAN line, Open circuit or broken CAN harness, Failed instrument cluster or ABS/PCM module, Low system voltage or weak battery, Water intrusion into a connector or module. The specific cause varies by vehicle.
How much does it cost to fix U1900 on a Saab?
Repair costs vary widely with the root cause and Saab model; each issue on this page carries its own estimate where one is published.
Looking for U1900 on a different make?
View U1900 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.