At Mr.Car, you can book fault code reading and clearing or in-depth computer diagnostics of a specific fault. Complex diagnostic tasks are handled by a dedicated specialist with more than 20 years of experience.
Fault code reading and computer diagnostics — what is the difference?
Reading and clearing fault codes
Reading stored codes from the accessible control units and clearing them if necessary. Finding the cause of the fault is not included.
Computer diagnostics
Finding the cause of a specific fault by analysing live vehicle data, reviewing diagnostic information, testing possible causes, taking the necessary measurements and carrying out additional checks.
A fault code is a starting point, not a diagnosis in itself. The same code can be related to the component itself, its power supply, wiring, connectors, operating conditions or another system. That is why replacing a part based solely on a fault code does not always eliminate the cause of the fault.
When to book diagnostics
- the Check Engine light is on or flashing;
- the engine is hard to start, runs unevenly, stalls or has lost power;
- the car goes into limp mode;
- fuel consumption has increased for no obvious reason;
- ABS, ESP or SRS/airbag warnings have appeared;
- the transmission shifts harshly or with a delay, or shows a fault message;
- intermittent electrical faults occur;
- the Webasto heater won't start, shuts off or runs erratically;
- the fault appears only with a cold engine, after warm-up, under load or in certain conditions.
The absence of a fault code does not mean the car is free of faults. A mechanical or intermittent fault may not set a code, so where necessary diagnostics include physical checks and measurements.
How diagnostics work at Mr.Car
-
We clarify the problem
We find out when the problem started, under what conditions it appears and what work has been done before.
-
We define the initial scope
We separate simple code reading from a full search for the cause. The customer can set a spending limit in advance, within which no further approval is needed.
-
We collect data
We read information from the accessible control units and analyse the car's live data, fault code status, data stored at the moment the fault occurred (freeze frame) and other available diagnostic information.
-
We test possible causes
Depending on the task, we use electrical and mechanical measurements, an oscilloscope, a smoke machine, checks of fuel pressure, compression, the vacuum system, injectors, sensors, actuators, wiring and CAN/LIN, and other methods. If necessary, a test drive with data monitoring is carried out.
-
We identify the cause and agree on the next step
It is not always possible to tell in advance exactly how long the search will take. Additional diagnostic time, disassembly and separate work are agreed with the customer.
-
We check the result after the repair
After the repair, Mr.Car carries out a follow-up diagnostic check and verifies that the original fault has been eliminated.
Diagnostic equipment and methods
For diagnostics we use universal and specialised systems: Launch, Autel, Bosch KTS, BMW ISTA, ODIS and VCDS. The choice of equipment depends on the car, the system and the specific diagnostic task.
Diagnostic equipment provides data but does not replace a specialist's analysis. With complex faults, the conclusion is based on the combination of data, measurements and checks needed to confirm the cause.
Systems we diagnose
- petrol and diesel engines and engine management systems;
- automatic transmissions, including ZF and DSG;
- ABS, ESP and SRS/airbag;
- starting and charging systems: battery, starter motor and alternator;
- electrical equipment, wiring, sensors, actuators and communication between control units;
- climate control systems and air conditioning;
- Webasto and parking heaters;
- DPF and EGR — diagnostics of system operation and fault finding;
- turbocharging, vacuum and fuel systems, injectors;
- ADAS — fault code reading and analysis of system data.
Mr.Car does not service electric vehicles or carry out work on high-voltage traction batteries.
If ADAS or another highly specialised task requires calibration or the work of a dedicated specialist, Mr.Car arranges that stage through a partner or a visiting specialist. The customer receives the car back from Mr.Car once the work is complete.
Specialised diagnostics and prices
| Service | What it includes | Price |
|---|---|---|
| Reading and clearing fault codes | Fault codes from accessible control units; finding the root cause is not included. | €25 |
| Computer diagnostics | In-depth search for the cause of a specific fault. | from €50 |
| ZF and DSG transmission diagnostics | Diagnostic information, live data and analysis of transmission operation. | from €50 |
| Webasto diagnostics | Fault codes, operating data and finding the cause of the heater fault. | from €50 |
| Engine borescope inspection | Visual inspection of the accessible internal surfaces of the engine. | from €15 / cylinder |
| Suspension diagnostics | Checking the condition of suspension components, play and signs of wear. | €25 |
| Pre-purchase inspection | Vehicle inspection, fault code reading and paint thickness measurement. | €80 |
The price of in-depth diagnostics depends on the complexity of the fault and the time needed to confirm the cause. If work needs to continue, additional costs are agreed with the customer. Any disassembly needed for access is charged as separate work.
ZF and DSG transmission diagnostics
Harsh shifts, delayed gear changes, limp mode or transmission fault messages require separate diagnostics. At Mr.Car, ZF and DSG transmission diagnostics start from €50. Diagnostic information and live data are assessed alongside the transmission's actual operation and, where necessary, additional checks.
Webasto diagnostics
If the Webasto won't start, shuts off after starting, produces excessive smoke or runs erratically, we diagnose the system and determine the scope of further repairs. Webasto diagnostics from €50.
Suspension diagnostics
Knocking over bumps, play, vibration, poorer handling or uneven tyre wear may call for a physical check of the suspension. Suspension diagnostics at Mr.Car cost €25.
Pre-purchase inspection
There is a separate service for assessing a used car: a vehicle inspection, fault code reading and a paint thickness check with a gauge. The price is €80.
Engine borescope inspection
A borescope allows us to inspect accessible internal engine surfaces without dismantling the engine and identify visible signs of wear or damage. Depending on the engine design and where access is possible, we can, for example, look for scoring on cylinder walls and inspect piston surfaces, deposits and other accessible areas.
The price starts from €15 per cylinder. If access to the cylinders is difficult and additional disassembly is required, that work is charged separately.
Photos and video are provided at the customer's request. If the images need explaining, our service adviser explains the result in plain language. Borescope inspection complements diagnostics but does not replace compression testing and other methods when they are needed.
Coding, adaptations and programming
As part of diagnostics and repairs, Mr.Car performs control unit coding, adaptations and basic settings, battery registration, injector coding, transmission adaptation, service interval resets and other operations supported by the diagnostic equipment. Whether control units can be programmed and factory software updated is determined individually for the specific car and task.
If an operation requires specialist expertise, Mr.Car arranges for the specialist to carry it out. The customer does not need to find a separate service provider.
What the customer receives after diagnostics
- a checklist with the current fault codes;
- a consultation with our service adviser and an explanation of the necessary next steps — depending on the customer's request;
- recommendations for the next stage of checks or repair;
- photos and video from the borescope inspection — at the customer's request;
- after the repair — a follow-up diagnostic check and verification that the original fault has been eliminated.
When you need urgent help
A flashing Check Engine light, especially with strong vibration and loss of power, may indicate misfires and a risk of damage to the catalytic converter. Stop safely and check what to do next in the owner's manual and with a specialist.
An oil pressure or engine overheating warning is a reason to stop safely and switch off the engine. If braking or steering gets worse, fuel is leaking or the engine stops while driving, the first priority is to arrange safe transport to the workshop.
A steadily lit amber warning light with no noticeable change in how the car runs also needs checking. What a specific warning means and whether you can keep driving depend on the car and the situation.
How to prepare for diagnostics
- give the make, model, year, registration number and, if needed, the VIN;
- describe the symptom and when it first appeared;
- specify the conditions: cold or warm engine, acceleration, braking, load, rain, frost, etc.;
- tell us which warnings appear and whether they stay on;
- tell us about recent repairs, battery disconnection, cleared fault codes and parts already replaced;
- if the fault is intermittent, keep a photo of the message or an audio recording made safely.
Do not try to recreate a dangerous situation just to record it, and do not film while you are driving.
Frequently asked questions about car diagnostics
What is the difference between computer diagnostics and fault code reading?
Fault code reading shows the codes stored in the accessible control units. Computer diagnostics means finding the cause: analysing the car's live data, testing possible causes and taking the necessary measurements. Reading and clearing codes costs €25; in-depth diagnostics start from €50.
Can a faulty part be identified from the fault code alone?
Not always. The code helps to determine where to look, but the cause may be the component itself, the power supply, wiring, connections or another system.
There are no fault codes, but there is a problem. Can diagnostics help?
Yes. Not every mechanical or intermittent fault sets a code. Data analysis, electrical or mechanical measurements and checking the car under the conditions in which the fault appears may be required.
Can I just clear the fault code and see if it comes back?
Clearing a code does not remove the cause and may erase data that is useful for troubleshooting. Where necessary, codes are cleared after they have been read and the initial information has been assessed.
How long do diagnostics take?
It is not always possible to determine the exact time in advance. If additional time is needed, further work and costs are agreed with the customer.
Do you check ABS, airbags and the transmission?
Yes. Mr.Car diagnoses ABS/ESP, SRS/airbag systems and transmissions. Separate diagnostics for ZF and DSG transmissions are available from €50.
Do I need diagnostics before buying a car?
Computer diagnostics are useful as part of the check but do not replace a physical inspection. A separate pre-purchase inspection costs €80 and includes an inspection, fault code reading and a paint thickness check with a gauge.
Should computer diagnostics be done every year?
There is no universal mandatory interval for fault finding. Diagnostics are needed when there are symptoms, warnings or a specific task.