The emissions and exhaust system of the Peugeot 307 is prone to faults that often appear unexpectedly. Diesel models in particular regularly suffer from warning lights coming on, clogged particulate filters and exhaust parts that rot away. These problems can lead to loss of power and MOT failure if you do not tackle them in time. Find out which issues are most common and what you can do about them.
Why does the exhaust of the Peugeot 307 rot away so quickly?
The exhaust of the Peugeot 307 has a solid reputation when it comes to premature corrosion. Owners report that the back box and centre section in particular are susceptible to rust. This is because the materials used in the exhaust system are not always optimally protected against moisture and salt.
The service life of the exhaust system depends heavily on how you drive. Short journeys make the problem worse because the system does not fully warm up. As a result, condensation remains in the silencers and pipes, which speeds up rust formation. By regularly driving longer distances, where the system warms up properly, you can get more years out of your exhaust.
On average you can expect a lifespan of five to eight years for the back box, depending on use and maintenance. The catalytic converter and the front part of the system often last a little longer. As a preventive measure you can regularly check the underside of your car for rust and treat early signs of corrosion with protective products.
Emission fault Peugeot 307: how do you use OBD2 diagnostics?
The emissions warning light on the Peugeot 307 often comes on without any noticeable loss of performance. This makes it difficult to estimate the cause without diagnostic equipment. An OBD2 scanner is therefore essential for every 307 owner who regularly has to deal with this problem.
The most common fault code is P0108, which points to a problem with the MAP sensor. This fault causes jerky acceleration, especially in cold weather. Faulty wiring to the sensor or problems with the tone ring can also trigger this code. Other common codes relate to the particulate filter, the additive tank or the engine management.
When reading fault codes it is best to follow these steps:
- Connect the OBD2 scanner to the diagnostic port under the dashboard
- Read out the active and stored fault codes
- Write down the codes and look up the exact meaning for your model
- Clear the codes after fixing the problem and reset the ECU
- Do a test drive to check whether the light comes back on
Owners recommend always resetting the ECU after repairs to the emissions system. Some faults otherwise remain stored in the memory even when the problem has been resolved. Note that the light sometimes also comes on due to a leaking additive tank (a tank for an additive fluid that supports the particulate filter) on diesel models with a particulate filter.
Particulate filter Peugeot 307 clogged: what are the symptoms?
A clogged particulate filter is one of the most common complaints on diesel versions of the 307, especially the 2.0 HDi. The problem often occurs on cars that make a lot of short trips. The system then does not reach operating temperature and cannot regenerate the particulate filter.
You can recognise a clogged particulate filter by several symptoms:
- Loss of power during acceleration
- Emissions warning light on
- Higher fuel consumption than normal
- Car goes into limp mode in case of severe blockage
- Raised idle speed
With a clogged filter you can try to regenerate the system by doing a longer motorway drive. Drive for at least 20 to 30 minutes at a constant engine speed of around 2,500 revolutions per minute. This brings the exhaust system up to the right temperature to burn off soot particles.
If this does not help, professional cleaning or replacement is necessary. Note that after replacing the particulate filter you must also top up the Eolys additive (a special fluid that supports regeneration of the particulate filter). This additive helps with the regeneration process and is important for the lifespan of the new filter. Do not forget to reset the system after replacement, otherwise the warning light will stay on.
What are the consequences of a leaking exhaust system for the MOT?
A leaking exhaust system almost always leads to MOT failure. The test checks for both visible leaks and excessively high emission values. On the Peugeot 307, a non-gas-tight exhaust is common due to corrosion at the weld seam and joints.
The MOT test checks the following points in particular:
- Visible holes or cracks in the exhaust system
- Leaks at welded joints and flange joints
- Exhaust gases escaping before the catalytic converter
- Emission values above the legal limit
- Loose or damaged mounting brackets
A lit emissions warning light is also a reason for failure. The tester checks whether all warning lights operate correctly and may fail the car if the light is on during the test. This makes it important to resolve faults in the emissions system in good time.
With a leak in the front part of the exhaust, before the catalytic converter, you often cannot pass the emissions test. Unburnt gases then escape before they have been cleaned, resulting in excessively high readings. A leak after the catalytic converter usually causes fewer problems with the emissions test, but is still a reason for failure because of noise pollution and safety.
‘ So replace the fuel filter as a first step in the case of recurring emission faults, before you replace expensive components such as the particulate filter. ’
Common problems with sensors and additive tank
In addition to the particulate filter and exhaust, sensors and the additive system are also weak points. The MAP sensor regularly gives faults, especially in cold weather. This leads to codes in the engine management and jerky acceleration.
The additive tank (a tank for additive fluid that supports the particulate filter) on diesel models is another well-known weak spot. This tank contains Eolys fluid, which helps regenerate the particulate filter. The tank and the associated pump regularly leak, causing a warning light to come on. You can often recognise leaks by traces of fluid under the car or a chemical smell.
The fuel filter also plays a role in emission faults. A clogged filter can lead to incomplete combustion and therefore a warning light. So replace the fuel filter as a first step in the case of recurring emission faults, before you replace expensive components such as the particulate filter.
Practical tips for maintenance and prevention
Regular maintenance prevents many problems with the emissions and exhaust system. Drive at least once a week on a longer trip to bring the system up to full operating temperature. This helps regenerate the particulate filter and prevents condensation in the exhaust.
On cars with more than 100,000 kilometres, check the key components as a preventive measure. Have the MAP sensor, the fuel filter and the condition of the particulate filter checked before they cause problems. This prevents you from being stranded with a warning light on and possible loss of power.
When replacing exhaust parts, choose quality components with a good warranty. The back box and catalytic converter are readily available for the 307 and are often affordable. After any repair to the emissions system, clear the fault codes and reset the system. Otherwise, some faults remain stored in the memory even though the problem has been resolved.
The Peugeot 307 SW shares the same problems as the hatchback, with extra attention needed for the particulate filter on 2.0 HDi engines. Regular checks and timely repairs keep this car reliable for daily use. On the Carnews website you can find more information about common problems with the Peugeot 307 and other models. Discover useful tips and detailed technical information to help you maintain your car.
Frequently asked questions
Common problems include the emissions/engine management warning light coming on, a clogged particulate filter (especially on diesels) and faulty or contaminated sensors (such as the MAP sensor). You can recognise this by warnings such as “antipollution fault”, irregular or jerky acceleration, higher fuel consumption and sometimes loss of power. Leaks or faults in the additive tank/pump (Eolys fluid) are also common, recognisable by recurring emissions faults despite normal driving behaviour. An OBD2 diagnosis and inspection of the particulate filter, additive tank, sensors and fuel filter are the first steps when dealing with these issues.
Have your exhaust system regularly checked for leaks, rust and mountings, and replace wear parts such as silencers, particulate filter and (on diesels) Eolys additive in good time according to the schedule. Once a week or once a fortnight, take a longer journey at motorway speed to allow the particulate filter to regenerate properly and prevent clogging. Replace the fuel filter and (MAP) sensors preventively at higher mileages and have fault codes read immediately with an OBD2 scanner if an emissions light comes on. When replacing parts, always choose quality components and, after repairs, make sure the ECU and the particulate filter system (DPF/Eolys) are correctly reset.
The main MOT requirements for the emissions system are that no warning light for the exhaust gas/emissions system is on, that the particulate filter (on diesels) and catalytic converter function correctly and that the measured emissions remain below the legal limits. Make sure the particulate filter does not become clogged (regularly making longer journeys), that the Eolys additive is topped up and that the system has been correctly reset after any work. Replace the fuel filter and any faulty sensors (such as the MAP sensor) in good time and have fault codes read and resolved if a warning light comes on. Shortly before the MOT, have a diagnosis and emissions test carried out so that any problems can still be fixed.
Possible upgrades include a sports back box or cat-back system, a high-flow catalytic converter and in some cases a fully custom stainless-steel exhaust system. Advantages are a sportier and fuller sound, slightly better throttle response and, in combination with tuning, a small increase in power. Disadvantages include more noise in the cabin (drone on the motorway), higher costs, the risk of MOT failure or issues with emissions regulations, and potentially higher insurance or inspection sensitivity. On diesel models you must be particularly careful with modifications around the particulate filter because of legal and technical risks.
A defective or poorly functioning emissions or exhaust system on a Peugeot 307 can lead to higher fuel consumption, for example due to a clogged particulate filter or incorrectly operating sensors causing the engine management to inject more fuel. Performance can deteriorate due to loss of power and poorer acceleration, especially if the particulate filter is blocked or the exhaust gas flow is restricted. In addition, the engine may run more roughly, noise levels may increase and a warning light may come on, all of which negatively affects the overall driving experience. With timely diagnosis and replacement or cleaning of the filter, sensors and exhaust parts, the 307 usually returns to normal driving behaviour.