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
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 onIf 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
The ABS, airbag or another light is onWe also read the computer that turned on the light, not just the engine. More about the ABS light- The light comes on and goes offThe 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 lessThe fault shows which system the problem is in.
The technical inspection is in a few daysUnder 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
You are buying a used carBefore you pay, you see the faults and whether they were cleared recently.- The car has just been repairedWe check that the fault is really fixed, then clear the faults.
You changed the oil, but the dashboard still asks for a serviceWe 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
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
