What does the P1850 fault code mean when the car won't start?

[VanRiley]

P1850 fault code, applicable to Audi and Volkswagen, means the Controller Area Network data link has lost information from the Engine Control Module. Here are specific details about automotive fault codes: Background: The Controller Area Network, abbreviated as CAN, is an automotive communication protocol that allows devices on the network to communicate directly with each other without requiring a host to control the communication. The Engine Control Module, also known as the Engine Control Unit, controls the operation of the entire engine. Its main function is to control the optimal fuel injection amount and ignition timing. Clearing fault codes: After troubleshooting the vehicle issue, it's necessary to clear the fault codes. When clearing fault codes, strictly follow the specific clearing method designated for that vehicle model. Never attempt to clear automotive fault codes by disconnecting the battery's negative terminal, as this may cause abnormalities.

[TeaganRose]

When encountering the P1850 trouble code with the engine failing to start, based on my years of experience in car repair, this is usually due to an issue with the transfer case differential lock solenoid valve circuit in the four-wheel-drive system. A circuit malfunction can cause the vehicle control system to prevent the engine from starting to protect the transmission. Common causes include aging or broken wires, blown fuses, or the solenoid valve itself being stuck, which is particularly common in humid conditions or high-mileage vehicles. During repairs, I first use a diagnostic tool to read detailed fault codes, check for loose or corroded wiring connections, and then test the solenoid valve's resistance. If not addressed promptly, it may lead to damage to other electronic components. Therefore, I recommend towing the vehicle directly to a professional repair shop for inspection to avoid bigger issues on the road. Avoid forcing the engine to start to prevent damage to the engine control unit.

[MacJulia]

My SUV also threw the P1850 trouble code last year and wouldn't start. I was really panicked at the time, thinking it was a dead battery, but replacing it didn't help. Later, the auto mechanic diagnosed it as a short circuit in the differential lock circuit of the 4WD system, caused by loose wiring connections that triggered a system error preventing startup. It took a few hours to fix the connections, and then everything returned to normal. The mechanic said wiring wear in older cars is the main culprit, as daily bumps can easily cause connection issues. Actually, this code is quite common, especially when temperature changes cause wires to expand and contract, leading to faults. Don't try to disassemble it yourself—finding a reliable repair shop to diagnose it properly can save time and money. Safety first, after all.

[VanRuth]

Seeing the P1850 fault code and the engine won't start, as a car owner, I simply summarize: it indicates that the 4WD differential lock solenoid valve is faulty or there's a wiring issue, and the vehicle's safety system may prohibit ignition startup as a result. Check the fuse box for any blown fuses or if the wire connectors are loose or water-damaged. If these fixes don't work, a professional should use a computer scan to pinpoint the exact problem. Avoid forcing a startup to prevent further damage—get it repaired early for peace of mind.