[Home](https://autoindustrija.rs/en)[All services](https://autoindustrija.rs/en/services) # Car diagnostics A warning light is on or the car runs badly? We read the faults from every computer in the car and explain what is urgent and what can wait. [How you get the price ↓](https://autoindustrija.rs/en/services/car-diagnostics#cena) [Call 067 774 1606](tel:+381677741606)[Message us on WhatsApp](https://wa.me/381677741606) Send us the **make, model, year** and what you notice. We work in several cities in Serbia. Tell us your city. ## A warning light is on? How urgent it is The colour and the flashing of the light tell you whether you may drive on. * The yellow engine light stays on Finish the drive calmly No hard acceleration or high revs. Call us for diagnostics as soon as you can. * The engine light flashes or is red Stop as soon as it is safe A more serious fault, it can damage the catalytic converter. Switch off the engine and call us. * ABS, airbag or another light We read every computer Some readers see only the engine. They do not see these faults. ### When else people come for diagnostics The car jerks or pulls less We look at the faults and sensors while the engine runs. A diesel loses power We read the particulate filter data. [More about DPF cleaning](https://autoindustrija.rs/en/services/dpf-cleaning) The light comes on and goes off The fault stays recorded for some time. [Read the explanation below](https://autoindustrija.rs/en/services/car-diagnostics#brisanje-greske) Before the vehicle inspection You see in time a fault the inspection checks. [Read the explanation below](https://autoindustrija.rs/en/services/car-diagnostics#pre-tehnickog-pregleda) Before buying a used car You see the faults and whether they were cleared recently. [Read the explanation below](https://autoindustrija.rs/en/services/car-diagnostics#pre-kupovine-polovnog-auta) Service reset After an oil change the dashboard stops asking for a service. Already have a fault code from a reader? Send it with the make, model and year, and we will tell you what to check first. [Call](tel:+381677741606)[Message us on WhatsApp](https://wa.me/381677741606) ## How much does car diagnostics cost You do not replace a part blindly. Price Cars do not have the same number of computers, so there is no single price. We tell you the price when you send the make, model and year, before the work. Payment Cash or through a company. Place and time Tell us your city, we agree it by phone. [Send the make, model and year](https://wa.me/381677741606) What the price depends on * The make, model and year of the car. * How many computers your car has. * Whether the fault needs extra checks. ## What you get The same fault can have several causes. So we tell you what to check first, so you do not pay for a part that was not broken. * Reading every computer: engine, gearbox, ABS, airbags, air conditioning and the other systems your car has * On diesels, faults of the particulate filter and of the sensor that shows how full the filter is ### Important * **The repair is a separate job.** Diagnostics tell you where to look for the fault. An electrical fault is found and repaired by an [auto electrician](https://autoindustrija.rs/en/services/auto-electrician). * **Diagnostics do not replace a check of the brakes, suspension, tyres and oil leaks.** ## How we do diagnostics 1. 1 ### You tell us what you notice Send us the make, model and year. Tell us when the fault appears: with a cold or warm engine, in town or on the motorway, and after what it started. 2. 2 ### We tell you the price and book a time We tell you the price when you send the make, model and year, before the work. Work starts only when you agree. 3. 3 ### We read every computer in the car We plug the device into the OBD port and read the faults from all computers. When the fault does not say enough, we watch live engine data. 4. 4 ### We explain what is urgent You get a list of faults and an explanation of each one in words: what is urgent, what can wait and what is an old fault that has already been solved. 5. 5 ### We clear the faults once the problem is fixed After the repair we clear the recorded faults. When needed, we also reset the service reminder. ## A fault says where to look, not which part to replace A car has several computers. Each one constantly watches its part of the car and records a fault when something does not work as it should. A fault says what the computer noticed, not which part to replace. ## Clearing a fault does not fix it Clearing only switches off the light. If the fault is still there, the code comes back. That is why we clear faults after the repair, not instead of it. Once the fault is fixed, the engine light usually goes off by itself. The light can also go off when the computer does not notice the fault for a while. The fault still stays recorded for some time, so we read it during diagnostics. ## Diagnostics before the vehicle inspection At the vehicle inspection, the system that warns of a fault in the exhaust emission parts is checked through the OBD port. That warning is the engine light. It is checked on petrol cars from 2001 and diesels from 2004. So call us for diagnostics a few days before the inspection, so you know in time what needs fixing. [More about OBD at the vehicle inspection](https://autoindustrija.rs/en/advice/relocated-obd-port-inspection) ## Diagnostics before buying a used car The seller can clear the faults before the sale, so the light is off. After clearing, the car has to be driven for a while before it checks its systems again. During diagnostics we see whether those checks are complete. If they are not, the faults may have been cleared recently or the battery recently disconnected. Then ask the seller why. On newer cars the mileage is also stored by the engine, ABS or airbag computers. If the mileage was not changed in all of them, diagnostics can show that the figures do not match. That is not reliable proof, but it is a reason for a further check. [More about rolled-back mileage](https://autoindustrija.rs/en/advice/rolled-back-mileage) ## The particulate filter on diesels The particulate filter (DPF) catches soot from the exhaust and cleans itself while you drive. Frequent short trips, on which the engine does not warm up, can stop the cleaning. So can faults in the fuel injection or the EGR valve. Then the engine makes more soot. When the filter gets too full, the car goes into reduced power, so the engine is not damaged. Driving then no longer helps. During diagnostics we read the faults and the filter data. [More about DPF cleaning](https://autoindustrija.rs/en/services/dpf-cleaning) Updated 27 October 2026. ### Fault code P0300 The first letter tells you the part of the car: * **P**Engine and gearbox * **C**Brakes, ABS, steering and suspension * **B**Airbags, air conditioning and the rest of the cabin * **U**The link between the computers in the car [More about OBD diagnostics](https://autoindustrija.rs/en/advice/obd-diagnostics-explained) ## Questions How much does diagnostics cost? It depends on the car. We tell you the price when you send the make, model and year, before the work. What if the light comes on again after the repair? Get in touch and we will read the faults again. My OBD port has been relocated. Do diagnostics work? Yes, if you bring the adapter. The factory port stays in its place, but diagnostics do not work until the small adapter is in the hidden port. With the adapter in place, we plug the device into the factory port as before. [More about a lost OBD adapter](https://autoindustrija.rs/en/lost-obd-adapter) ## Send us the make, model and year Also tell us what you notice. We tell you the price before the work. [067 774 1606](tel:+381677741606) [Call](tel:+381677741606)[Message us on WhatsApp](https://wa.me/381677741606) Email: [kontakt@autoindustrija.rs](mailto:kontakt@autoindustrija.rs) ## Related services ### Auto electrician Electrical faults: alternator, starter motor, wiring and lights. [More about the auto electrician](https://autoindustrija.rs/en/services/auto-electrician) ### DPF cleaning A clogged DPF: cause check, regeneration, cleaning or a new filter. [More about DPF cleaning](https://autoindustrija.rs/en/services/dpf-cleaning) ### Coding We turn on features your car already has. [More about coding](https://autoindustrija.rs/en/services/car-coding) ### Vehicle inspection Inspection at an authorised station and the new sticker at the same place. [More about the vehicle inspection](https://autoindustrija.rs/en/services/vehicle-inspection) --- Page on the website: https://autoindustrija.rs/en/services/car-diagnostics auto-industrija, Belgrade. Phone and WhatsApp: +381677741606. E-mail: kontakt@autoindustrija.rs.