# Car computer diagnostics: price and what it shows _Updated: 8 November 2026_ **Short answer:** We'll tell you the price of computer diagnostics for your car up front, once you send the make, model and year. It depends on how many computers we read, which tool your make needs and whether the fault needs further checks. > **The service we recommend: Diagnostics** We read faults from every computer in the car and tell you what is urgent. We tell you the price when you tell us the model. [More about the service](https://autoindustrija.rs/en/services/car-diagnostics) ## What the price of computer diagnostics depends on There is no single price, because cars do not have the same number of computers. A new, more expensive car can have as many as 150 computers. **The price depends on** - **How many computers we read:** just the engine or the whole car, with the gearbox, ABS, airbags and air conditioning. - **Which tool your make needs:** any reader reads exhaust faults, but the other computers need a tool for your make. - **Whether the fault needs further checks:** when the fault does not say enough, we follow the engine live. ## How we do computer diagnostics The tool is plugged into the OBD port, under the steering wheel on most cars, and every computer in the car is read, not just the engine. When the fault alone does not say enough, the engine state at the time of the fault and live engine data are checked. Diagnostics shows where the fault is, and the repair is a separate job. We repair electrical and electronic faults as a separate service. [More about the auto electrician](https://autoindustrija.rs/en/services/auto-electrician) ## What computer diagnostics shows Diagnostics shows the faults the computers in the car have stored. The computers constantly watch the engine, gearbox, brakes and other systems. When they notice a fault, they store it. With a more serious fault they also turn on a warning light, but the light does not say what the fault is. Every fault has a code of one letter and 4 digits. The letter tells you which part of the car the fault is in: - **P**: engine and gearbox. - **C**: brakes, suspension and steering. - **B**: air conditioning, airbags, infotainment and driver assistance systems. - **U**: the connection between the computers in the car. A fault says what the computer noticed, not which part to replace. That is why we check the part before it is replaced, so you do not pay for a part that was not broken. ## What diagnostics does not show Diagnostics does not show worn brakes, suspension, steering and tyres. It only sees what the computers in the car have recorded, and these show up when the car is inspected. ## When it is time for computer diagnostics - **The engine warning light has come on:** If the amber light is on steadily, you can finish your journey, and get in touch for diagnostics as soon as possible. [More about the engine warning light](https://autoindustrija.rs/en/advice/check-engine-light) - **The ABS, airbag or another light is on:** We also read the computer that turned on the light, not just the engine. [More about the ABS light](https://autoindustrija.rs/en/advice/abs-warning-light) - **The light comes on and goes off:** The fault only appears now and then. The light goes off by itself when the computer does not see the fault for several drives in a row. The fault stays stored for some time, so we can read it. - **The engine runs unevenly, jerks or pulls less:** The fault shows which system the problem is in. - **The technical inspection is in a few days:** Under the Serbian vehicle inspection rulebook, the engine light is checked through the OBD port, on petrol cars from 2001 and diesels from 2004. Have diagnostics done a few days before the inspection. [More about OBD at the technical inspection](https://autoindustrija.rs/en/advice/relocated-obd-port-inspection) - **You are buying a used car:** Before you pay, you see the faults and whether they were cleared recently. - **The car has just been repaired:** We check that the fault is really fixed, then clear the faults. - **You changed the oil, but the dashboard still asks for a service:** We reset the service reminder, so it starts counting from the beginning. If the engine light flashes, the fault can damage the catalytic converter, so get in touch straight away. ## Clearing a fault does not fix it Clearing only turns off the light, and the fault stays. If the fault is not repaired, the fault and the light come back. Once the fault is repaired, the light usually goes off by itself. Clearing the fault also clears the record of the engine conditions when it happened. Without that record, we cannot see under which conditions the fault appeared. That is why we clear faults after the repair, not before it. After clearing, the computer has to check all systems again. For that the car needs to be driven normally, usually for about a week. If the light comes back in that time, the fault is not fully fixed. ## On a used car you can see that faults were cleared recently A seller can clear the faults before the sale, so no light is on. Diagnostics then shows that the car has not yet finished its checks, so you can see the faults were cleared recently. If the car supports it, you can also see how many kilometres it has driven since the faults were cleared. The checks also stay unfinished when the battery was recently replaced or disconnected. So ask the seller about the battery as well. [More about checking a used car](https://autoindustrija.rs/en/advice/used-car-stolen-check) The computers in the engine, ABS and airbags also record kilometres. If the mileage was not changed in all of them, it can show up on diagnostics. [More about rolled-back mileage](https://autoindustrija.rs/en/advice/rolled-back-mileage) ## Frequently asked questions ### I already have a fault code from a reader. What next? Send the code on [WhatsApp](https://wa.me/381677741606), together with the make, model and year of the car, and we'll tell you what needs checking. [More about OBD diagnostics](https://autoindustrija.rs/en/advice/obd-diagnostics-explained) ### Which makes do you do diagnostics for? Send us the make, model and year, and we'll tell you before the appointment whether we work on your car. ### Does diagnostics work if the OBD port has been relocated? It does. Bring the adapter you got with the relocation and plug it into the hidden socket. The diagnostic tool then connects to the factory OBD port, as before. [More about a lost OBD adapter](https://autoindustrija.rs/en/lost-obd-adapter) Have a question about your car? Message us on WhatsApp or call 067 774 1606. ## Read also - [Car dashboard warning lights: meaning and when to stop](https://autoindustrija.rs/en/advice/dashboard-warning-lights) - [Check engine light (engine warning light): what it means and what to do](https://autoindustrija.rs/en/advice/check-engine-light) - [Car won't start: what to check first](https://autoindustrija.rs/en/advice/car-wont-start) --- Page on the website: https://autoindustrija.rs/en/advice/car-computer-diagnostics auto-industrija, Belgrade. Phone and WhatsApp: +381677741606. E-mail: kontakt@autoindustrija.rs.