Why can't the OBD be read at the vehicle inspection station?

[VonMaggie]

If the OBD cannot be read at the vehicle inspection station, it may be due to a malfunction of the diagnostic tool or because the diagnostic tool does not support the communication protocol of the car's ECU. In such cases, it is recommended to try using a different diagnostic tool. The ECU, known as the brain of the engine, is present in every car and is responsible for controlling the engine's operation. If the car is equipped with an automatic transmission, there will also be a TCU, which is the computer for the automatic transmission. Without the TCU, the automatic transmission cannot function properly. The TCU collects various information through sensors and, after processing, controls the transmission shifting via actuators.

[LeLorenzo]

I've dealt with many cases where OBD readings fail during vehicle inspections. Usually, the issue lies with a dirty or damaged OBD port, which can be cleaned with a hairdryer or soft cloth. Blown fuses are also common—check the relevant positions in the car's fuse box, especially in older vehicles. Loose or disconnected wiring is another frequent problem, such as poorly secured plugs or rodent-chewed cables. Scanner tool incompatibility can also be a factor, as different car models support different protocols, and inspection station equipment might be outdated—try switching tools. The engine must be in the 'on' state, and low battery voltage can interrupt readings. Once, I helped a car owner diagnose interference from an aftermarket dashcam, which resolved the issue after removal. Timely repairs can prevent inspection delays, saving both time and money.

[LandonDella]

Last time during my vehicle inspection, the OBD just wouldn't read no matter what. After struggling for hours, I found the port was clogged with too much dust affecting the connection - a quick blow to clean it solved the problem. Some people overlook the ignition switch position - the engine needs to be running, otherwise the device can't communicate. Aging batteries with unstable voltage may also cause issues; test results showing below 12 volts are dangerous. Sometimes the inspection station's equipment malfunctions - try another station or bring your own adapter. I once encountered corroded wiring that took some repair time to pass inspection. Developing habits like regular port cleaning and battery checks can significantly reduce headaches.

[VonAriana]

When OBD cannot read data, start with the basics: clean the interface to ensure it's free of dust and dirt; check if the fuse is blown and replace it in the box; try testing with a different scanner; confirm the engine is running and the battery is healthy. If these steps don't work, it might be a wiring fault or module damage, requiring professional inspection. Sometimes, inspection station equipment has poor compatibility, so there's no need to worry.