U2105 on Saab: How to Diagnose & Fix
CAN Bus — No Communication With ECM/ECU (Manufacturer-Specific)
1 Saab model · 1 documented issue · 1 critical
U2105 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, where floor-level wiring and connectors run. 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.
Sources for this issue (2)
U2105 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 U2105 mean on a Saab?
U2105 stands for "CAN Bus — No Communication With ECM/ECU (Manufacturer-Specific)." U2105 is a manufacturer-specific CAN bus code that generally means a module reported no communication with the engine control module (ECM/ECU) over the network. When the ECM cannot be reached, engine-related coordination breaks down, which can cause drivability problems, no-start conditions, or multiple warning lights. Because it can affect the engine controller, it should be addressed promptly. On Saab it is documented across 1 model: 9-3.
What are the most common causes of U2105?
The most common causes of U2105 are: ECM not powered (blown fuse, failed relay), Damaged or open CAN bus wiring to the ECM, Faulty engine control module, Loose or corroded ECM connector, Poor ground or high-resistance ground, Low or unstable battery voltage, Module configuration / programming error. The specific cause varies by vehicle.
How much does it cost to fix U2105 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.