How to repair the U1900 fault code?

[OMax]

U1900 fault code repair method is to turn off the ignition switch, remove the negative ground cable of the battery, unplug the ECU wiring connector, and reinstall it to eliminate the fault. The following are relevant information about the battery: 1. Lifespan: The normal lifespan of a car battery is generally around two years; 2. Maintenance: If properly maintained, it can be extended, with the best lasting up to about four years. Signs of a dead car battery: The car is difficult to start after being parked for two days, and the car becomes noticeably heavier when driving with the air conditioning on. 3. Precautions for car batteries: Modern car batteries have protective functions and retain the minimum power required for ignition. If you turn on the key without starting the engine, you can listen to music or turn on the lights for about an hour.

[ElisaFitz]

Last time my car threw a U1900 trouble code, which really annoyed me. This thing is a communication fault, mainly related to the CAN bus system in the vehicle. When I encounter this situation, I usually start by disconnecting the battery for ten minutes to let the computer reboot, then reconnect the OBD to see if the fault is still there. If the light is still on, then it's time to carefully check the wiring. I went through the engine bay, mainly checking the wiring harness near the ABS module for water damage or rodent bites. When I couldn't find the issue, I just replaced all the fuses in the car—sometimes poor contact can cause false trouble codes. Oh, and remember to perform a network test with the diagnostic tool after repairs. My neighbor Old Zhang skipped this step and had to redo the job three times.

[Cox]

I'm quite familiar with the U1900 trouble code issue. Just last week, I helped a neighbor deal with it. First, remove the gateway computer under the seat and check if the gold fingers are oxidized or blackened. Clean them with alcohol wipes and reinstall. Then, use a multimeter to measure the voltage of the two CAN bus signal wires—normally, it should stay around 2.5 volts. If the voltage is off, trace the wiring from the gateway to the airbag computer. Once, on a BMW, I found water had soaked the junction box under the carpet—just drying it out fixed the problem. The key is the troubleshooting sequence: start with a software reset, then check hardware connections, and finally inspect data interruption nodes. I recommend buying an ELM327 diagnostic cable to run a full vehicle scan with a computer—it's more reliable.

[VanZoey]

To handle the U1900 fault, I usually follow four steps. First, reset the vehicle's computer by disconnecting the power for ten minutes. Then, check if any module connections are loose, especially the fuse box under the steering wheel. Next, use a diagnostic tool to scan the working status of the ABS and transmission modules. Finally, inspect the physical connections of the bus and measure the terminal resistance from the ECU to the gateway with a test pen. Recently, I encountered an issue with a corroded TCM module on a Sagitar, which was resolved by replacing it for 300 yuan. Remember, never rush to clear the fault codes; always identify the root cause first.

[SanElisa]

Last month, we received three vehicles with U1900 faults at the workshop, and found that the main issues were in the electrical circuits. The most challenging one was the Wuling, where we discovered that cockroaches had entered the body control module and caused a short circuit on the motherboard. To handle such communication faults, you need to prepare an oscilloscope to check if the CAN waveform is normal. If the signal is unstable, you should measure the resistance in segments. Start by inspecting the wiring harness behind the dashboard, which is the most prone to problems, with a focus on the purple twisted pair. For Ford vehicles, pay special attention to the wiring harness bracket near the battery, as the metal plate can easily wear through the wires. A trick my mentor taught me is to spray some rust remover in the OBD port, which can solve most connection issues.