Failed the APK (MOT) on the exhaust: leak, noise, DPF or emissions

Your inspection report shows a rejection point for the exhaust or the emissions. What does that wording mean, and what needs to happen before the car passes? The APK is the compulsory Dutch vehicle inspection, comparable to the British MOT. Below we translate the requirements from the APK manual of the RDW (the Dutch vehicle authority) into plain language and explain how we repair the rejection point.

By the team at Autobedrijf Willemsbrug, RDW-approved APK (MOT) test station since 1979 · Updated 6 November 2026

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The short answer

At the APK, a car fails on the exhaust if the exhaust leaks, is not securely fitted or makes too much noise, or if the emissions do not meet the requirements. The requirements are in article 5.2.11 of the RDW APK manual. A rusty exhaust that does not leak and is securely fitted is not a rejection point. After the repair, the car has to be inspected again. If we repair the items that failed, we will also arrange the retest. We will tell you the cost of the repairs and the retest in advance.

Exhaust repairs at Autobedrijf Willemsbrug: we first check whether a repair is enough. We weld, replace a single part or make a section to measure, and we replace catalytic converters and oxygen sensors after a diagnosis. We do not clean, replace or remove diesel particulate filters. We tell you the price in advance based on your registration number. Call +31 10 479 00 00. You bring the car and we call you when it is ready. A loan bike is free while one is available. Bringing the car on a Saturday is possible by arrangement. Our team speaks English. More about exhaust repairs

On which points does the exhaust fail the APK?

The inspector looks at two things: the condition of the exhaust itself and what comes out of it. The inspection report uses a fixed description with the code 5.*.11. The asterisk stands for the type of vehicle. For a passenger car it is 5.2.11. These are the rejection points from the RDW list of inspection items (keuringsaspectenlijst). We give the Dutch wording as it appears on the report, with a translation:

Wording on the report (Dutch) What it means Which cars
Uitlaatsysteem niet gasdicht What it meansThe exhaust leaks somewhere along its length, including at the turbo or the EGR valve Which carsAll cars
Uitlaatsysteem ondeugdelijk bevestigd What it meansThe exhaust is loose or not hanging properly on its mountings Which carsAll cars
Geluidsniveau hoger dan toegestaan What it meansThe exhaust makes more noise than allowed Which carsAll cars
CO meer dan wettelijk toegestaan What it meansToo much carbon monoxide in the exhaust gases Which carsPetrol and LPG
Lambdawaarde wijkt af What it meansThe ratio of air to fuel is outside the limit Which carsPetrol and LPG with a catalytic converter
Emissiebestrijdingssysteem niet compleet What it meansThe catalytic converter or the oxygen sensor is missing or not working Which carsPetrol and LPG with a catalytic converter
Absorptiecoëfficiënt te hoog What it meansToo much soot in the smoke test Which carsDiesel without a compulsory DPF
Roetfilter niet aanwezig of duidelijk defect What it meansThe diesel particulate filter (DPF) is missing or visibly broken Which carsDiesel with a DPF according to the vehicle register
Roetfilter werkt niet (goed), aantal deeltjes meer dan toegestaan What it meansThe particle counter test finds too many soot particles Which carsDiesel with a DPF according to the vehicle register

Source: RDW APK manual, list of inspection items and article 5.2.11 (noise and environment). Consulted November 2026.

The list of inspection items has no advisory points for the exhaust, only rejection points. What else is checked at the APK is explained on our page about the APK at our garage in Rotterdam.

A leak or a loose exhaust: what does the inspector check?

According to article 5.2.11, paragraph 1, the exhaust must be gas-tight along its full length, apart from the drain holes. Paragraph 2 says the exhaust must be securely fitted. The inspector checks this by eye and by ear, with the engine running and the car over an inspection pit or on a lift.

  • Drain holes are allowed: some silencers have a small hole that lets condensation water out. That does not count as a leak.
  • The turbo and EGR valve count: according to the manual, the turbo and the EGR valve (the valve that feeds part of the exhaust gases back into the intake) are part of the exhaust system. They must not leak exhaust gas either.
  • Exception for some diesels: leakage past the injectors of certain common-rail diesels is not an exhaust leak for the purposes of the APK.
  • Last section missing: if the last section of the exhaust is missing, the car fails.
  • Mounting: cracked rubber hangers or rusted-through brackets can mean the exhaust is no longer securely fitted.

Rust on the exhaust is not a rejection point in itself. What counts is leaks, mounting and noise. According to the ANWB (the Dutch motoring organisation), rust does eventually cause holes, so that the exhaust starts to leak. Rust usually starts at the rear silencer.

Too much noise: what is the limit?

The inspector judges the noise by ear. Where needed, the inspector measures it with a sound level meter. The limit depends on what is in the vehicle register:

  • With a noise value in the vehicle register: the noise at the exhaust outlet must not exceed that value plus 2 dB(A) (paragraph 3).
  • Without a noise value in the register: no more than 95 dB(A), measured at 3,500 revs per minute for a petrol engine or 2,000 revs per minute for a diesel (paragraph 4).

An exhaust that is too loud often has a hole or a rusted-through silencer. Which noise points to which problem is explained in exhaust noise: rumbling, rattling or hissing.

Failed on emissions: CO, lambda value or catalytic converter

For a petrol car, the inspector measures the exhaust gases. According to the Dutch government (Rijksoverheid), cars built in 1993 or later get a four-gas emissions test if they have a petrol engine, or an LPG engine with a regulated catalytic converter. This test shows whether the car’s emissions stay within the legal limits.

  • Lambda value: at raised engine speed, the lambda value must be between 0.97 and 1.03, according to paragraph 6. A deviation points to a mixture that is too rich or too lean.
  • Catalytic converter and oxygen sensor: according to paragraph 8, a petrol car first registered after 31 December 1995 must have a properly working emission control system consisting of a catalytic converter and an oxygen sensor.
  • A reading instead of a measurement: for cars up to 3,500 kg first registered after 31 December 2005, the inspector may read the on-board diagnostic system (EOBD). If that reading is in order, without fault codes, it replaces the measurement (paragraph 10).

If the engine warning light is on, the inspector measures the exhaust gases. According to the APK manual, a car can no longer fail on an EOBD reading alone. More on this in engine warning light on: will your car fail the APK.

If the car has failed on emissions, that does not automatically mean the catalytic converter is broken. A leak in the exhaust, an oxygen sensor or an engine fault can also be the cause. That is why we first read the fault codes and take measurements. See also catalytic converter fault: is it the converter or the oxygen sensor.

Diesel: DPF, particle counter test and smoke test

Does your diesel have a diesel particulate filter (DPF) according to the vehicle register? Then the inspector counts the soot particles in the exhaust at the APK. If there are too many, the car fails. According to the Dutch government, this test has been a compulsory part of the APK since 1 January 2023. The inspector also checks that the DPF is present and not clearly defective. How the test works is explained in the APK particle test: what it means for your diesel.

If the DPF has been removed without this being reported to the RDW, the car fails. According to the RDW, some passenger cars with a factory-fitted DPF and a date of first registration before 1 January 2017 can have the DPF details removed from the register. The car then no longer fails on this at the APK, but you do pay the particulate surcharge on road tax (fijnstoftoeslag).

A diesel without a DPF in the vehicle register gets a smoke test. If it fails, the report says “Absorptiecoëfficiënt te hoog” (absorption coefficient too high).

Failed on the DPF? We do not clean, replace or remove diesel particulate filters. We do find the cause of the fault and tell you what is needed.

Can I still drive a car that failed on the exhaust?

That depends on the rejection point and on whether your APK is still valid. What the law says after a fail is explained in failed APK: repairs and retest in Rotterdam. From a safety point of view, we use this rule:

Can I still drive? Is the exhaust hanging loose or touching the road? Then do not drive on. Can you smell exhaust fumes inside the car? Open the windows and have the car checked soon. Exhaust gases contain carbon monoxide. If the car failed on noise or emissions and your APK is still valid, you can drive to the garage. You will not notice every leak by its smell, so do not wait too long. If you are in doubt, call +31 10 479 00 00.

What do we do after a fail on the exhaust?

We repair the rejection points and arrange the retest at one address. Bring the inspection report or a photo of it. It shows which point failed. This is how it works:

  1. Investigation: for a leak, a loose exhaust or too much noise, we find the problem on the lift with the engine running. For a fail on emissions, we first read the fault codes and take measurements.
  2. First checking whether a repair is enough: welding, replacing a single part or making a section to measure is often possible. According to the ANWB, small holes can sometimes still be welded or sealed with a special paste.
  3. Price in advance: we tell you one price in advance, based on your registration number. We only carry out repairs with your approval.
  4. Repair: we weld, replace rubber hangers, clamps or a single part such as a silencer or the flexible section, and replace the catalytic converter or the oxygen sensor if the diagnosis points to it.
  5. Retest: if we repair the items that failed, we will also arrange the retest. We will tell you the cost of the repairs and the retest in advance. We carry out the APK Monday to Friday.

We do this for all makes, including vans and motorhomes up to 3,500 kg. You bring the car and we call you when it is ready. Bringing the car on a Saturday is possible by arrangement. How we repair and replace exhausts is explained on our page about exhaust repair and replacement in Rotterdam.

Frequently asked questions

Does a rusty exhaust fail the APK?

No, not on rust alone. The car fails if the exhaust leaks, is not securely fitted or makes too much noise. The RDW list of inspection items has no advisory points for the exhaust either. Over time, though, rust can make an exhaust leak, so have it checked.

Will my car fail if the engine warning light is on?

No, not for that reason alone. According to the APK manual, a car can no longer fail on an EOBD reading alone. If the engine warning light is on, the inspector measures the exhaust gases. If they are not in order, the car fails on emissions.

Is a leak at the turbo or the EGR valve also an exhaust leak?

Yes. According to article 5.2.11 of the APK manual, the turbo and the EGR valve are part of the exhaust system and must not leak exhaust gas. Leakage past the injectors of certain common-rail diesels does not count as an exhaust leak.

Will my diesel fail if the DPF has been removed?

Yes, if the DPF has been removed without this being reported to the RDW. Some passenger cars with a factory-fitted DPF and a date of first registration before 1 January 2017 can have the DPF details removed by the RDW. The car then no longer fails on this, but you do pay the particulate surcharge on road tax.

Can I have the retest done at your garage?

Yes. If we repair the items that failed, we will also arrange the retest. We will tell you the cost of the repairs and the retest in advance. We are an RDW-approved APK station in Rotterdam-IJsselmonde. Call +31 10 479 00 00.

Do you repair a DPF that failed?

No. We do not clean, replace or remove diesel particulate filters. We do find the cause of the fault and tell you what is needed. We do repair exhaust leaks ourselves, and we replace catalytic converters and oxygen sensors ourselves after a diagnosis.

Failed on the exhaust? We repair and arrange the retest

Call +31 10 479 00 00 and have your registration number and the inspection report to hand. We will tell you the cost of the repairs and the retest in advance.

You will find us at Boterdiep 11 in Rotterdam-IJsselmonde, close to Stadion Feijenoord (De Kuip). We work by appointment. For a quick question or check you can walk in without an appointment.

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