Vehicle Diagnostic Check
in Wing, Leighton Buzzard
What is a vehicle diagnostic check?
A vehicle diagnostic check is a process that uses a diagnostic computer to report on your car’s electronic systems, and identify any faults within many different control units. Some vehicles now have 50+ modules as standard. Cars are now equipped with electronic control units (ECUs), which continuously monitor various sensors. This includes, but is not limited to, the engine, automatic transmission, and brakes.
During a diagnostic check, live data may also be viewed to track down an issue, such as engine air flow readings, fuel trims, sensor readings, and fault statuses. This helps build a clearer picture of the vehicle’s overall condition, and leads to a more detailed test plan.
Diagnostic checks are not limited to identifying faults that have already triggered warning lights. They can also reveal hidden faults that you may not have noticed in day to day driving.
When there is a fault in the system, the ECU records a fault code, and may trigger one of several warning lights on your dashboard. A diagnostic involves connecting a scan tool to your car’s OBD port to retrieve fault codes. These codes can sometimes provide valuable insight into what may be causing the issue, but is often only the first step of a good diagnostic procedure. A test plan is then put together after carrying out a scan, and then systems are tested to pinpoint an issue with the vehicle. Sometimes this may require extra time, depending on the complexity of the problem. Proper testing is the key to a first time fix without having additional problems, however, this isn’t always simple due to the complexity of many issues a vehicle develops.
A diagnostic check is an essential part of modern car maintenance. It provides a way to identify issues, improve performance, and ensure your vehicle remains safe and reliable.
How do I know if my car needs a diagnostic test?
There are several signs that your vehicle may need a diagnostic test carried out. The most obvious is a warning light on the dashboard, such as the engine light, ABS light, or other system faults. These lights indicate that the vehicle’s onboard computer has detected a fault that requires attention.
Not all problems trigger warning lights immediately. These are a common occurrence and are intermittent faults, which often require a lot more time to diagnose. You may notice changes in how your car drives, such as reduced performance intermittently. These symptoms can indicate underlying issues that a diagnostic check can help to track down.
Common warning lights we see:
Engine warning light – The engine warning light is one of the most common issues we see in our workshop. It can be triggered by something relatively minor, such as a faulty sensor, but it may also be a more complex problem like wiring faults. Because there are many possible causes, it’s essential to carry out a professional diagnostic check first.
ABS light – The anti-lock braking system is designed to prevent your wheels from locking up during emergency braking. If the ABS warning light comes on, your regular braking system will still function as normal. However, the ABS system itself may not operate correctly in an emergency situation.
TPMS light – The tyre pressure warning light usually indicates that one or more of your tyres have dropped below the recommended pressure for the car. In many cases, the light is triggered by a slow puncture, but it can also be caused by faulty TPMS sensors.
It’s also worth completing a diagnostic check as part of routine maintenance, especially if your vehicle has covered a lot of miles. Regular diagnostics can help detect intermittent or developing faults, so it can be seen as preventative maintenance.
Frequently asked questions
How long does a diagnostic test take?
A standard diagnostic check typically takes 1 hour+, depending on the complexity of the issue. Retrieving fault codes is usually quick, but additional time will be required to investigate further, check live data, and carry out a test plan.
Will the garage explain the results?
Yes, the diagnostic test will always be explained clearly without using too much technical jargon. Technicians will outline any fault codes found, and what repairs are recommended to fix the problem. An estimate for the work required will also be provided.
What does the check engine light mean?
The check engine light indicates that the vehicle’s computer has detected an issue with the engine system. This could be caused by a lot of different issues. It could be something as simple as a loose fuel cap, or could be an engine misfire. Making a note of symptoms before bringing the vehicle in to be checked is important.
If the light is flashing, it usually indicates a more serious problem that could cause damage if ignored, and therefore, the vehicle should be inspected as soon as possible. Along with a flashing light, you may have reduced power, making the car difficult to drive.
Should I get a diagnostic check immediately if a warning light appears?
Yes, it’s recommended to have a diagnostic check carried out as soon as possible when a warning light comes on. While some issues may be minor, others can develop into serious faults if ignored. We have seen cases where ignored sensor faults can lead to blocked diesel particulate filters (DPFs), increasing the cost of repairs.
Can diagnostics detect intermittent faults?
Yes, diagnostic systems can sometimes detect intermittent faults, especially if the vehicle’s computer has logged fault codes from previous occurrences. Even if the issue is not currently active, stored codes can sometimes help provide a direction for testing. This isn’t always the case, as sometimes, the fault must be replicated to come up with a test plan.