New OBD checks to be introduced to NCT from Monday

In an effort to meet Ireland’s strategic objectives and in accordance with EU Directive 2014/45, the National Car Testing Service (NCTS) will commence the use of OBD testing as part of the NCT from next Monday, June 21.

Ireland will be one of the first of the EU Member states to implement this new approach of testing which will help contribute to significantly safer vehicles on Irish roads.

From June 21, a new version of the NCT manual V5.0 (June 2021) will come into operation. The NCT manual lists each item on which a car will be tested. It lays down the test method and pass/fail criteria to be adopted for the compulsory road-worthiness testing of passenger vehicles. It provides guidance in relation to why a vehicle may fail the NCT and the categorisation of defects.

From the same date, OBD testing will become an inspection item in the NCT and will be introduced on a phased basis.

An On-Board Diagnostics System (OBD) is a computer system inside a vehicle, that tracks and regulates a car’s performance. It collects information from sensors inside the vehicle, to alert the user to a problem, often before it becomes a major issue.

Initially, when an OBD error code is detected it will result in the vehicle receiving an “Advisory Pass”. Then, from early 2022, when an error code is detected, this may constitute a reason for “failure”, according to the NCTS.

The NCT vehicle inspector will plug the OBD scanner into the vehicle’s OBD computer port known as the DLC (data link connector). This port is usually located under the steering wheel but may also be found in the glove compartment of the vehicle.

This OBD scanner will quickly indicate whether or not error codes exist, and it also helps and alerts the vehicle inspector to possible defects within the vehicle.

In order to conduct the inspection, the NCTS has advised customers to ensure that their glove compartments are unlocked and clear of personal belongings before their NCT, and that any devices using the OBD port in the vehicle are removed in advance of the test.

The OBD scanner will scan the OBD system for the Vehicle Identification Number (VIN) and Odometer Reading, both being included on the vehicle inspection report.

Any error code associated with the electronic braking system and/or the antilock braking system, will also be recorded on the vehicle inspection report provided to the customer following their NCT inspection.

The NCTS says that while vehicles with error codes will initially be recorded as ‘Advisory Pass’, it recommends that any error codes be addressed by the vehicle repairer.

However, the vehicle will not need to return for re-inspection for these items alone, the NCTS says.

From early 2022, should certain error codes be detected, they will constitute a reason for failure in the NCT. An NCT certificate will not be issued until the items are rectified and a pass result is achieved, according to the NCTS.

Meanwhile, the new NCT manual identifies that, where a combination of deficiencies is recorded in the NCT in one area of a vehicle, this could lead to the result of the NCT being escalated to ‘fail dangerous’.

In such instances, the NCTS says that the deficiencies are considered to constitute a direct or immediate risk to road safety and the vehicle should not be driven on the road under any circumstances, in accordance with The Road Traffic (National Car Test) Regulations 2017, S.I. 415 of 2017.

The new manual is updated in line with Directive 2014/45 (EU) and is available for download on the NCTS website ( and Road Safety Authority website (

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