Diesel Particulate Filters

Peugeot Citroen diesel particulate filter

A diesel particulate filter (DPF) is a device designed to remove diesel particulate matter (PM) or soot from the exhaust gas of a diesel engine. The DPF captures and stores the particulate matter and then uses heat to burn off the accumulated PM, preventing it from being released into the atmosphere. It is an important component of the emissions control system of diesel engines, as it helps to reduce the harmful effects of diesel emissions on both human health and the environment.

A diesel particulate filter regenerates through a process called “passive” or “active” regeneration. In passive regeneration, the high exhaust temperatures generated during normal driving are used to burn off the accumulated particulate matter. However, if the vehicle is not driven at high enough speeds or for long enough distances, this process may not occur, leading to clogging of the filter. In active regeneration, the engine management system injects additional fuel into the engine to increase exhaust temperatures and initiate regeneration. Some vehicles also use a catalyst coating on the DPF to assist with the regeneration process.

It is important to note that if the regeneration process is not completed successfully, it may result in costly repairs or replacement of the filter. Other potential causes of DPF failure include faulty engine sensors or injectors, poor fuel quality, or malfunctioning EGR valves. Therefore, regular maintenance and proper use of the vehicle can help avoid DPF issues.

Changes to MOT rules regarding headlamp conversions

Section 4.1.4 of the current MOT inspection manuals for both motorcycles and cars and passenger vehicles states ‘Existing halogen headlamp units should not be converted to be used with high intensity discharge (HID) or light emitting diode (LED) bulbs. If such a conversion has been done, you must fail the headlamp.’

Class 3, 4, 5 and 7 vehicles
For class 3, 4, 5 and 7 vehicles, the defect ‘Light source and lamp not compatible’ only applies to vehicles first used on or after 1 April 1986.

Should a vehicle be presented for an MOT test with conversions before 1 April 1986 they must not be failed with immediate effect.

Vehicles presented with converted halogen headlamp units first used on or after 1 April 1986 will continue to be failed.

Headlamps must comply with all other requirements of the test and headlamp aim.

Source: MOT special notice 01-21: headlamp conversions – GOV.UK

TPMS Diagnostic Health Check

Tyre pressure monitoring systems (TPMS) have been fitted to cars for many years but recently TPMS has become mandatory for all new vehicles and has become a testable item for the annual MOT inspection.

Two main technologies exist; indirect and direct TPMS. Indirect systems detect wheel speed rotation differences resulting from a deflated tyre by using inputs from the ABS wheel speed sensors. This technology was unreliable and could not detect tyre deflation in more than one wheel. All modern vehicles are fitted with direct TPMS which includes a pressure sensor in each wheel which transmits readings to a control unit using radio signals. The driver’s information display can then, in most cases display the tyre pressures for each wheel and warn the driver if a tyre suffers an unexpected pressure loss.

Like with all complex electronic systems, faults can occur with TPMS components resulting in the TPMS warning lamp illuminating. We have designed our TPMS Diagnostic Health Check to help identify the most common causes of unexplained TPMS warnings both quickly and cost effectively.

Our TPMS Diagnostic Health Check uses the latest dedicated TPMS diagnostic equipment and covers the following tests:

  • Checking and adjusting the tyre pressures in accordance with the tyre pressure placard.
  • Carrying out a scan of all TPMS sensors to check they are responding and reporting the correct tyre pressure.
  • Checking the sensor battery level*.
  • Carrying out a TPMS module fault code scan.
  • Carrying out a TPMS sensor ID comparison with the TPMS module*.
  • Carry out a TPMS sensor relearn procedure if required*.

* When vehicle is equipped with this function.

Our TPMS Diagnostic Health Check is suitable for vehicles equipped with direct TPMS. We can also carry out diagnostic work on indirect TPMS systems, please contact us for details. Further chargeable diagnostic and/or mechanical work may be required to resolve some TPMS faults.

Buying a Car? Get it Inspected!


One of my brother-in-laws passed his driving test last Thursday and promptly went out and put a deposit down on a ten year old Ford Fiesta from a local used car dealer.

He picked the car up at 6.00pm last night and no doubt being extremely excited went to collect his wife from work where the car then broke down. He’d had the car less than one hour.

I was called out and found the battery not just discharged but dangerous. The state-of-charge indicator in the top of the battery was showing red. I was told the car dealer had serviced the car prior to collection. As you can see from the photo above the oil filter hadn’t been replaced so it hadn’t been serviced at all. The bonnet wouldn’t lock down properly leaving it at risk of flying open when driving. The car also had a full MOT but the passenger side windscreen wiper blade was split. If they’ve missed a wiper blade what else have they missed?

This all could have been avoided if the car had been inspected prior to purchase and any repairs subsequently carried out by the car dealer checked before handing over any money. It doesn’t matter whether you’re spending £500, £5000 or £50,000 on a used car, it’s cheaper to get it inspected than to find yourself stranded miles away from home.

Which? The second-hand car I bought has a problem, what are my rights?

Exploding Battery Post

I arrived at work this morning to find a gentleman waiting outside for me. His car was at a garage in a West Hull village and whilst there an explosion had occurred at one of the two batteries which power this large four wheel drive vehicle. The garage wasn’t sure what had caused it to happen and didn’t want to get involved.

The only option was to have the vehicle recovered to my workshop so I could carry out a detailed inspection and my preferred recovery company was then contacted and transported the car during the afternoon.

It was quickly apparent that the damage was limited to the positive battery post of the main starting battery. The battery post had become so hot as to cause molten lead to be ejected from it onto the top of the battery. The battery terminal was now badly damaged too.

On inspecting the battery terminals on the other battery it was clear that they hadn’t been tightened up properly and were insecure. This causes a high electrical resistance which in turn produces a lot of heat. It’s this heat which caused the explosion and subsequent damage.

The repair was straightforward. A new battery and new Durite battery terminals which are far superior to the original ones.

And a word of warning. Car batteries are dangerous. Incorrect installation can cause the battery to explode. If your car needs a battery fitting leave it to a competent mechanic!